Diffractive optics: state of the art
Author(s):
Jari Turunen
Show Abstract
In diffractive optics macrostructured surface relief profiles or index-modulated media are employed to modulate electromagnetic fields in such a manner that a given optical function is achieved [1,2]. Diffractive elements range from linear gratings and microlenses to complicated structures that can shape or split a laser beam in a rather arbitrary manner, or display scenes or patterns that need not exist in the real world. In a sense diffractive optics can be understood as an extension of classical optics, in which macrostructured surface profiles of graded-index media are employed. In recent years both the design methods and the fabrication techniques have developed rapidly, and a large number of new applications have emerged. As a result diffractive optics has already become a mature technology, with considerable technological and commercial impact, in several of its application areas.
Near field optics and photon force
Author(s):
Satoshi Kawata
Show Abstract
For the future progress of the modern advanced sciences and engineering such as biological science, material science, quantum physics, and semiconductor and microelectronics industries, the nanometric-scale technology for manipulation, fabrication, control, observation, and analysis for ultra-small structures is required. If photons could interact with small and fine structures within the extent of subwavelength area, it would be helpful for the academic studies on the dynamics of single atom, single molecule and single cell and its engineering applications to the manipulation of molecules, cells, and mesoscopic devices in nanometric dimensions. However, as is well known, the minimum size of the focused spot size formed by photons is as wide as a half of the wavelength due to the diffraction limit.
Multiple aperture imaging system for lithography
Author(s):
R. Völkel
Show Abstract
An optical system will be presented which uses a stack of microlens arrays for the 1:1 imaging of extended object planes. The system is based on the well-known concept of multiple aperture imaging. A compact imaging system was discovered which is remarkable in that it provides a diffraction limited resolution of 3 μm free of distortion and magnification errors for large object and image areas. 5 μm resolution was demonstrated by using melting resist microlens arrays.
Catadioptric systems for sub-quarter micron lithography
Author(s):
Kag Hyeong Lee
Show Abstract
Nowadays, ArF excimer laser projection lithography has been spot lighted due to its potential high resolution applicable to 1 G Bit DRAMs( < 0.2μm design rule ). The unique refractive material in ArF excimer laser lithography is fused silica and there is no way to correct the chromatic aberration by combination of different materials. Hence, the catadioptric configuration is inevitable in this field.[1, 2]
Modification of the resolution limits of the photolithographic process due to nonlinear optical propagation effects in the resist layers
Author(s):
A. Erdmann
Show Abstract
The basic limitations of optical lithography are characterized by the minimum resolvable feature size dmin = k1λ/NA and the depth of focus dfoc = k2λ/NA2, where λ is the wave- length of light and NA the numerical aperture of the projection system. The parameters k1 and k2 depend on the imaging technology. Typical production values are k1 ≥ 0.7 and 1 ≤ k2 ≤ 2. The upper formulas are commonly used for the evaluation of the imaging process in air. The projection of the image into optically linear resists only scales these formulas according to its refractive index.
Analysis of x-ray interferometers for phase distribution measurement
Author(s):
T. Nakano
Show Abstract
The X-ray interferometers are analyzed as a tool to measure a phase distribution of X-ray beams transmitted through phase objects. We calculate beam width using a dynamical diffraction theory of a spherical wave. The width defines the image resolution. From these results, it is found that the X ray quadruple-Lane-case (LLLL) interferometer has high image resolution compared with the X-ray triple-Lane-case (LLL) interferometer.
Excited states and photoprocesses in the series lasers active molecules
Author(s):
A. E. Obukhov
Show Abstract
The experimentally made measure-ments and theoretical calculations of the photophysical properties of some new and also some known lasers-active lumino-phores emission and generated radiations in the wavelength interval ∆λoscmax ≈ 300−560 nm have been studied in a wide range of free molecules and solvent. We show that the method of a priory-structural modeling was created: structure and properties of molecules for the quantum-mechanical control of the properties of molecular excited states (Si, Ti)and electronic-vibration transitions.
Simple photosculpture techniques for making arrays of lenses with controlled aberration
Author(s):
M. C. Hutley
Show Abstract
Many of the popular techniques for the manufacture of microlenses do not offer proper control over the shape of the lens produced. This applies in particular to the melting of photoresist, to graded index lenses produced by ion exchange through a hole in a mask and to photothermal techniques. Although it is possible to influence the process by optimising some of the process parameters it is not in the true sense possible to control the final result. Two techniques which do offer proper control are binary techniques and "photosculpture". The purpose of this paper is to describe a simple variation of photosculpture applied to the manufacture of arrays of microlenses.
UV induced organic polymer micro-lens array
Author(s):
Heihachi Sato
Show Abstract
Micro-optical elements such as lens, array and diffraction grating are key devices in optical communication, signal processing, neural network and image processing. Thus far, there are several schemes to realize these micro-elements with glass material, e.g., casting with micro structured mold, shrinking effect of photo-sensitive glass and graded index caused by selective diffusion of metallic ions. However, those elements made of glass have some disadvantages, in mass producibility, flexibility, difficulty for making film, heavy weight and cost. In order to overcome these problems it is quite recommended to adopt organic polymer for micro optical elements.1)
Optical imaging and transforming by using planar integrated optics
Author(s):
Seok Ho Song
Show Abstract
A planar optic set-up[1] composed of free-space optical components integrated on a glass block makes signal connections between 2-dimensional array of input and output optoelectronic devices via 3-dimensional glass space. Taking advantage of the compactness, easy alignment and thermal/mechanical stability, it can provide a useful approach to realizing an optical interconnection system in a practical way[2]. Therefore the planar optics imaging and transforming can render much improvement in power requirement, cost in alignment and packaging, and component size for the imaging and transforming optics.
In this paper, we investigate the imaging and transforming properties of planar integrated optics. The space band-width product of the planar optical imaging can be maximized by adjusting the number of zigzag bouncing in the glass substrate. The non-uniform spacing between the orders of planar optical transformation, such as Fourier transform and fractional transform, can also be reduced by the use of a toric-shape lens instead of spherical lens. Some experimental results to verify those properties are presented.
F-theta mirror scanning optics
Author(s):
Hiromichi Atsuumi
Show Abstract
Ever since the world's first laser printer1) was introduced in 1975, the standard for scanning optics systems has been the fθ lens (FTL), however fθ mirror (FTM) systems have also been under consideration since roughly the same date. In 1977 a theoretical analysis of parabolic FTM was made2), and they were put to practical use in large-format printers. Since then, many papers and patents concerning FTM have been published 3). In October of 1990, a letter-size laser printer that used an FTM went on sale, and a related technical paper was released4), but FTL systems nonetheless remained the main choice for scanning optics. In the course of developing plastic FTL, we found out the usefulness of FTM, in particular on the advantages that come with making them out of plastic, and studied some FTM systems. As a result, we have arrived at an original structure built by combining rotationally symmetric aspherical FTM with an ABTL (aspherical barrel-shaped toroidal lens), that is applicable to high-resolutions of 600 dpi and above.
Combined structures for high efficiency diffractive optical elements
Author(s):
L. L. Wang
Show Abstract
It is possible to enhance the efficiency of diffractive optical elements(DOE), by multilevel structures, blazed structures, or by high frequency gratings. But for some purposes, in one DOE, one part is with 'big' structures and another part with 'small' structures. For example, the reflective beam shaping DOE for stripe laser diode. In this case, if only using the multilevel structures or blazed structures for the whole DOE, in 'small' structure area, is not easy to fabricate. On the other side, if only using binary structures for the whole DOE, in 'big' structures, the efficiency is not high enough. We propose a new method to combine the two structures in one DOE, for high efficiency and convenient fabrication.
Electromagnetic diffraction in high aperture optical systems
Author(s):
C. J. R. Sheppard
Show Abstract
The field distribution in the focal region of a high aperture optical system is calculated using an efficient method based on expansion into multipole components. Aberrations in high aperture systems are considered. Combinations of aberrations which form a complete, orthogonal and normalized set over a weighted spherical pupil are evaluated.
Behavior of digital hologram when they are represented in finite gray levels on a tv monitor
Author(s):
J. L. Juárez-P.
Show Abstract
In this work we show the behavior of digital hologram obtained with the Kirchhoff-Fresnel's integral when these hologram are written on a TV monitor and this monitor has a finite number of gray levels. The Kirchhoff-Fresnel integral is numerically evaluated and represented in the computer virtual space. When the integral obtained values are showed on the TV screen they are changed due to the number of gray levels. Therefore in the reconstruction step of the hologram obtained on the TV screen we expect some details deterioration in the obtained holographic image.
Holographic nonspatial filter for laser beams: 2D selection
Author(s):
Yu. L. Korzinin
Show Abstract
The present paper deals with new results on the development of a holographic nonspatial filter to be used for laser beam clean up. This is the problem which any user of laser radiation necessarily meets. At the present time it is usually solved by means of spatial filters (pinholes or single mode optical fibers) which are placed on the beam way. Such filters exhibit, however, some important drawbacks, namely, they are rather expensive, require a long time for their alignment, can not be used with powerful lasers. Recently [1,2,3] we reported theory and ffitt experiments on the development of a holographic optical element to be used for filtration of spatial frequencies in laser beams, which is a principally new solution of this task. Such elements have several advantages as compared with traditional elements, namely, they operate directly in laser beam, without its focussing, they are aligned considerably easier, may be used with high power lasers, and are cheaper in manufacturing. However, our previous investigations were devoted mainly to the development of a holographic filter which allows to select spatial frequencies only in one direction. In the current paper we present results on 2D selection of laser beams. The theoretical estimations and first experimental results [2] show the possibility to obtain a holographic filter with angular selectivity of 10-104 rad, that is close to the magnitude of the initial divergence of laser beam.
Manufacturing a multicolored line drawing hologram using galvanometer scanners
Author(s):
Kenichi Kimura
Show Abstract
We presented the method of making a line drawing hologram by the holographic contact duplicating method using galvanometer scanners at the ICO topical meeting in 1994[1]. Here we describe that we realize a multicolored line drawing hologram using the method. Figure 1 shows the optical apparatus that consists of a laser, a pair of galvanometer scanners, a rainbow hologram which reconstructs an image of a diffusing plate, and focusing lenses. To obtain a multicolored hologram, three rainbow holograms are prepared which recorded a diffusing plate at different spatial frequency respectively These three rainbow holograms are made of photoresist plate.
Neutron optical elements produced by holographic technique
Author(s):
U. Schellhorn
Show Abstract
Holographic gratings in photopolymers are useful tools in optics for cold neutrons. After explaining their advantage over photoresists, we are presenting the latest development in their technology as well as in their application. The successful construction of a neutron interferometer indeed established the novel holographic technique in neutron optics.
The lippmann hologram contact duplicator with galvanometer scanners
Author(s):
Tsuyoshi Uematsu
Show Abstract
We showed an advanced way to make a line drawing hologram using a holographic duplicating method with a pair of Galvanometer scanners at the ICO topical meeting in 1994. As the former system is based on the Rainbow hologram contact duplicating (RHCD) method, we can get only Rainbow holograms. Here, we report that we apply this RHCD method to the Lippmann hologram.
Criteria of image performance for high-precision imaging of sharp-edged 2-dimensional objects
Author(s):
Johannes Schlichting
Show Abstract
It is well known that in the case of very high precise reproducing of sharp-edged two- dimensional objects by imaging there are several and especially nonlinear influences. This is important in cases of fotolithography and of high-precision measurement of edge position. in this case there are high contrast objects like masks which leads to an essentially nonlinear interaction of diffraction, interference, and illumination in image generation. For this reason there is a nonlinear influence of wavefront distortion (aberrations of the imaging system) on image intensity distribution. /1/,/2/. Because of this reasons and the fact, that the design and adjustment /3/,/4/ of high performance optical systems has to take into account also very small residual aberrations, the question of optimum aberration balancing for edge imaging is worth to be considered in more detail.
Fluorescence imaging system (FIS): function and use in the assessment of vegetation
Author(s):
Moon S. Kim
Show Abstract
Our laboratories have developed a fluorescence imaging system (FIS) to acquire steady state fluorescence images at the wavelength centered at 450 nm, 550 nm, and 680 nm. The imaging system shows that fluorescence emission intensity from vegetation is not uniformly distributed across the surface of the leaf. Determination of steady state fluorescent patterns and measurements of fluorescence induction kinetics are of significant value. This system compliments non-imaging fluorescence systems by determining the areas of variability in samples.
Specular-optical autostereoscopic displays
Author(s):
Stephen A. Benton
Show Abstract
Three-dimensional displays that do not require viewing aids such as spectacles, termed "autostereoscopic" displays, present two or more distinct perspective views to two or more distinct viewing locations such that the viewer's two eyes may receive a stereo pair of images and perhaps may also move from side to side to enjoy further depth cues such as motion parallax. The management of the image-bearing light, and in particular its focusing or convergence to distinct viewing zones, is typically effected with the help of optical components at or near the apparent location of the image in space. Those components may consist of an array of micro-optical components such as cylindrical lenslets (a lenticular sheet, for example), or a single macro-optical component acting as a field lens or mirror (perhaps with a directional diffuser). The differences between these two design approaches, micro- and macro-optical, present different choices in determining whether the resulting spatial image will be ortho- or pseudo-stereoscopic, and also present different limitations to image depth based on diffraction by the relevant apertures. Following Weiss, we refer to the second category of optical systems, the macro-optical types, as "specular" autostereoscopic displays, even if some of the components are replaced with their Fresnel-optical equivalents (1).
Rainbow hologram recording on photothermoplastic media
Author(s):
Lev M. Panasyuk
Show Abstract
The report presents the results of rainbow hologram record on photothermoplastic media by He-Ne laser radiation. Hologram characteristics as depended on slit diaphragm width are studied in a case of dimple-natured relief formed on the medium's surface. The recorded holograms are characterized by the value of diffraction efficiency being up to 12% at holographic sensitivity values being not worse than 105cm2/J. Rainbow holography is among the most perspective approaches for visual observation of restored images in polychromatic light. Different media are used for holographic recording, comprising AgHal media, bichromatized gelatine layers, photoresists., chalcogenide vitreous semiconductors and others. Together with these media the use of two-layer photothermoplastic medium (PTPM) com- prised a photosensitive semiconductor layer and visualizing thermoplastic one, seems to be perspective. The characteristic feature of PTPM is a combination of high values of both pho- tosensitivity (up to 105 locro ) and resolution (up to 2000mm-1), developing processes being of a dry nature and rather operative (about 1s). The thinner thermoplastic layer, the higher resonant frequency of PTPM and the wider frequency band of record, allowing to realize the high quality recording of high-frequency holograms. The record of rainbow holograms on PTPM is preferable as well due to the relief-phase nature of recording that is rather convinient for copies making and holographic patterns stamping. To record the rainbow holograms we use the tape PTPM consisted of 1.5pm semiconductor heterostructure, As2S3 As2Se3, and 0.8iim thermoplastic layer based on bytilmethacrylat co-polymer with styren, been deposited in succsession on the metallized PETF-support. The influence of different parameters of PTP recording, such as medium temperature, coroning electrode potential and duration of PTPM charging, on the character of surface deformations forming the relief hologram on PTPM is studied. The diffraction efficiency (DE) of a hologram is found to reach the maximum value at dimple nature of surface deformation. When recording the holograms by making use of such process an interference band is reproduced by dimples arranged in a row; the dimple size is less than 1,um. For the regimes providing a dimple nature of the record (V = 6.2 -÷ 6.8kV, T = 60 + 70C, t = 0.8 + 4.5s) the dependence of DE on spatial frequency is studied.
Birefringence sheet polarizer suitable for different wavelength
Author(s):
Yansong Chen
Show Abstract
A birefringence polarizer is proposed, which has sheet form, large aperture, high extinction ratio, relatively large beam-splitting angle and even low cost, besides, it is suitable for different wavelength. This new kind of polarizer will be very useful in optical technology.
Design of narrowband high reflector
Author(s):
Yongchang Lin
Show Abstract
This paper proposes a new method by utilizing the ultrathin metallic film that has a property of n k to design narrowband high reflectors, derives a few of formulae about its spectral reflection properties and gives examples of the design.
Methylene-blue sensitized dichromated gelatin holograms, a study of optimum coating and processing parameters
Author(s):
H. Madjidi-Zolbanin
Show Abstract
The optimum conditions for preparing, recording and processing of Methylene-Blue Sensitized Dichromated Gelatin (MBDCG) depend on some atmospheric parameters of laboratory where the operations are carried-out and the optimum value of different parameters approprite to different conditions must be determined by experiment. In this paper these conditions as well as the quality control of DCG plates and the diffraction efficiency (DE) of holographic gratings registered on these plates are reported.
Critical light reflection from curved liquid surface and apptication for measuring contact angle
Author(s):
Run Cai Miao
Show Abstract
Critical tight reflection, interforence and diffraction from raised and depressed curved liquid surface were discovered and its extraordinary intensity distribution photographed. Their formation and characters were discussed as wet 1, Furthermore, The applications formeasuring contact angle were discribed and experimental results were reported.
Design of a flight simulator used in training pilots
Author(s):
Lin Li
Show Abstract
A flight simulator, which is a precising optical instrument based on the theory of virtual reality used in training pilots, has been introduced in this paper. The scheme and the design methods for the flight simulator have been also presented.
The effect of exposure quantity as a catalyst on the development reaction in the fabrication of holographic phase diffraction grating
Author(s):
Byeong Ho Yun
Show Abstract
A new method for analyzing the refractive index modulation of the holographic phase diffraction grating is presented with the chemical mechanisms of wet processing. It is proved that the exposure quantity reacts as a catalyst at developing process and promotes the velocity of development reaction time fast. The experimental investigation has revealed that the good holographic phase gratings with diffraction efficiencies(<70%) could be taken, if the development reaction time were controlled in the 50 350[,a--- J/cm2] range of exposure quantity.
Merit functions of CCD cameras based on edge image processing
Author(s):
A. Simon
Show Abstract
We present a comparative study between two experimental methods to determine the modulation transfer function (MTF) and the merit functions of the CCD arrays as detectors in optical-digital correlators. The first method is the standard Foucault test.The second one is based on edge digital image processing. We also search to obtain the cuttof-frecuency of arbitrary optical digital correlator. The results are commented.
General conception of a Gaussian light beam
Author(s):
Won Don Joo
Show Abstract
Propagation of a general incoherent Gaussian light beam in free space and through an optical system in paraxial approximation is considered. It is shown that such a beam is described using the same parameters as for a classical coherent Gaussian beam. Kogelnik's " A BCD" law is also true for a general Gaussian beam.
Characterization of aliased fresnel hologram by pixel phase error function
Author(s):
Raimo Silvennoinen
Show Abstract
We present what is to our knowledge the first experimental observation of the controlled intensity fluctuations of aliased Fresnel holograms of an 8pmx8pm pixel size by using an analytical function for calculating optical phase errors from the pixel area of an aperture of synthetic Fresnel holograms.
Design of a viewing lens for virtual reality
Author(s):
Yongtian Wang
Show Abstract
The design principles of a viewing lens for virtual reality are discussed, and a design example given. Used with a 2.2" colour LCD, the system gives a 120° field of view for each eye. Monochromatic and chromatic aberrations are corrected for all the points in the field, while the large barrel distortion of the lens is compensated by a reverse compression of the image on the LCD. The system can establish a good stereoscopic view with a strong sense of immersion.
Stray light suppression baffle with radial leaves
Author(s):
Mangzuo Shen
Show Abstract
In this paper, we propose a new type of optical baffle with radial leaves, which can effectively reject stray light caused by primary mirror scatter while makes the baffle length shorter than the ordinary one. The stray light test setup for measuring the Point Source Transmittance (PST) of such an optical baffle is described. The test results show that this type of optical baffle can well suppress the stray light from an out-of field light source.
Optical imaging of small structures in optical lithography: high focal depth with optical filters.
Author(s):
R. Hild
Show Abstract
The main goal in photolithography is to produce smaller and smaller structures with high Depth of Focus (DOF). In this contribution the image intensity of small isolated structures is studied under the influence of nonuniform pupils. Special interest is dedicated to axial apodizing filters, which produce high DOF with sufficient small line width. The influence of partial coherent illumination has been taken into account.
High-efficiency second-harmonic generation of copper vapor laser and its application in sub-micron photolithography
Author(s):
Hong Ren
Show Abstract
Three approaches available to raise the conversion efficiency of the sec- ond harmonic generation of copper vapor laser in a BBO crystal have been demonstrated. The high optical conversion efficiency, 14.4%, was achieved at 5.4-W coppor vapor laser power. Sub-micron photolithography was attained using the second harmonic light of coppor vapor laser, a new UV light at 255.3-mxi, by a 1:1 catadioptric high NA lithog- raphy lens for the first time. The resolution of lines was 0.7-pm.
Power spectral analysis for evaluating optical near-field images of 20 nm gold particles
Author(s):
Uma Maheswari R.
Show Abstract
In spite of the very wide applications of a near-field optical microscope (NOM) in various fields such as observation of biological specimens, optical storage etc. [1,2], a systematic analysis of the images with respect to resolution and contrast is lacking. In this work using 20 nm gold particles (calibrated by electron microscope) fixed on a glass plate as the observation object, we have evaluated the transfer function of NOM.
Objects displacements measuring using Gabor functions
Author(s):
Jerzy Woznicki
Show Abstract
We present new method of measuring of the objects movements on the images. This method is based on Gabor functions representation of the images. We use a phase information of the complex Gabor function coefficients to compute a displacement vector.
Specular-optical autostereoscopic displays
Author(s):
Stephen A. Benton
Show Abstract
Three-dimensional displays that do not require viewing aids such as spectacles, termed "autostereoscopic" displays, present two or more distinct perspective views to two or more distinct viewing locations such that the viewer's two eyes may receive a stereo pair of images and perhaps may also move from side to side to enjoy further depth cues such as motion parallax. The management of the image-bearing light, and in particular its focusing or convergence to distinct viewing zones, is typically effected with the help of optical components at or near the apparent location of the image in space. Those components may consist of an array of micro -optical components such as cylindrical lenslets (a lenticular sheet, for example), or a single macro -optical component acting as a field lens or mirror (perhaps with a directional diffuser). The differences between these two design approaches, micro- and macro-optical, present different choices in determining whether the resulting spatial image will be ortho- or pseudo-stereoscopic, and also present different limitations to image depth based on diffraction by the relevant apertures. Following Weiss, we refer to the second category of optical systems, the macro-optical types, as "specular" autostereoscopic displays, even if some of the components are replaced with their Fresnel-optical equivalents 1.
Lens design using genetic algorithm in the stage of optimization
Author(s):
S. Vazquez-Montiel
Show Abstract
When optical systems are designed, the final stage corresponds to the optimization of an initial design, and frequently the methods of damped least squares are used. However, some methods as the one mentioned find local minimums and not the global one. Therefore, the solution depends mainly of the initial design. The method proposed in this work, is based in the genetic algorithms that find the global minimum, and besides an initial design is not necessary to begin the optimization process.
Photon tunneling scanning image separating method
Author(s):
Shifa Wu
Show Abstract
In 1991, American Patent Bureau Published the Patent of Photon Scanning Tunnel- ing Microscopy CUSP 5,018,865). Now we name that instrument 1st generation PSTM. Our group obtained first PSTM image of a holographic grating with resolution of 100nm october 1991, and super-resolution images with lateral beter than 10nm and longitude bet- ter than 1nm, using the 1st generation PSTM in 1993.
A new super-resolution optics with thick double-concave-cone lens for optical disc memories
Author(s):
Keizou Kohno
Show Abstract
To minimize the spot size of a light focused by a lens of optical disk system, other than adoption of higher NA lens or shorter wave length laser diode, super-resolution method has been examined. It is practically used in another products, but it is rare in optical head because of its light power loss. Light power loss is essential for optical head because output light of laser diode is rather weak, Super-resolution optics up to this time uses shield which covers central part of pupil of objective lens where the peak of light power exist, so it wastes much energy. In addition to it, most of all practical use optical heads (We choose this type of head for the standard.), a part of the Gaussian beam outer than the level about 28% of its peak is shaded by pupil of the objective lens.
Computer simulations of an autostereoscopic lenticular lens system
Author(s):
Bong-Ryeol Lee
Show Abstract
The lenticular lens is widely used to produce autostereoscopic images because of its simplicity. A lenticular lens system is composed of an LCD on which a lenticular lens is attached such that a pair of LCD pixel columns is roughly covered by a single lenticular lenslet. In this case, by the lenslet, the left and right pixel columns are optically separated and made incident to the left and right eyes of the observer, respectively, to produce parallax (see Fig. 1). A lenticular lens system contains a lot of parameters such as period of lenticular lens, focal length and focal position of the lens, period and size of LCD pixel, and observer distance. Since it is almost impossible to optimize a lenticular system in experiments with different lenticular lens sheets, we employ computer simulations to characterize the optical properties of a lenticular lens system and therefore optimize it.
Image formation in the near-field scanning optical microscope
Author(s):
Hiromitsu Furukawa
Show Abstract
The near-field scanning optical microscope (NSOM) has been developed to extract optical information from a nanometric area of sample. The amount of information contained in an NSOM image is potentially vast but it could not yet be fully exploited because of the need for a more complete understanding of the effects of the probe-sample interaction on the imaging process. A better understanding will lead to an unambiguous analysis of an NSOM image and will make the NSOM a reliable imaging tool. In this paper, we present the analysis of NSOM imaging through the numerical calculation based on an electromagnetic-theory-based algorithm,called Finite-Difference Time-Domain method (FDTD).
Imaging with a kilometer-long focal depth
Author(s):
Shu Wing Li
Show Abstract
By modifying the wavefront at the aperture of an optical system, it can be made to have a long focal depth. Computer simulation results of such an imaging system show that, images can be resolved over a distance longer than a kilometer.
Near-field optical microscope with ultrasonic resonance regulation and its application to quantum confined system
Author(s):
Xing Zhu
Show Abstract
Near-field optics has drawn wide attention in the last 10 years since it provides the possibilities of ultra-high resolution exceed the optical diffraction limit and local optical imaging and spectroscopy at the nanometer scale. One key problem in developing new type of scanning near-field optical microscope (SNOM) is the method of tip-sample regulation, which can keep the detecting tip in the near-field regime and should have little or no optical interference with the signals to be detected.
Gaussian pupil for superresolution at soft x-ray wavelength
Author(s):
Young Ran Song
Show Abstract
By using Gaussian pupil, the resolution limit eG can be made less than Rayligh's limit of resolution ER. The Gaussian form of the amplitude impulse Uo(x) is initially defined by e 'x2 and by Fourier transform relation the pupil function A(w) is obtained and then the amplitude impulse U(x) is derived for a finite aperture. It is shown EG is < 1/2 radius of the Airy disk = 1/2 ER in the system of NA=0.25 and 2=130nm(Soft X-ray). Also, it is shown the OTF of the annular Gaussian aperture depends only on the outer diameter of the pupil, which is a special feature of the Gaussian pupil. , .
Model for analyzing visual images of non-lambertian objects observed through a light-scattering medium
Author(s):
Vladimir V. Barun
Show Abstract
This paper presents an approach to treat the imag- ing of objects with arbitrary reflection diagrams. We consider here the observation of retroreflective objects through a light scattering medium. Their images formed by an active vision system show a number of surprises. First, a retroreflector may be perceived as several different objects. Its image, under uniform illumination and invariable reflec- tive characteristics, can be highly-nonuniform in brightness, etc. Second, a retroreflector with very low albedo viewed against an ideally-white back- ground may be seen as a clearer object than the background. These features should be accounted for when analyzing the imaging of objects with reflection patterns differing greatly from that of Lambertian ones.
Deformation of the speckle pattern under optical magnus effect
Author(s):
I. V. Kataevskaya
Show Abstract
An experimental investigation of the dependence of the angle of rotation of the speckle pattern of the light, transmitted through an optical fiber with a step refrac- tive index profile, on the angle a of entry of a narrow light beam into the fiber was carried out. It was shown that magnitude of the optical Magnus effect depended on this angle as a2.
Using of vitreous chalcogenide semiconductors in microelectronic fabrication
Author(s):
Lev M. Panasyuk
Show Abstract
This report describes the application of thin film Vitreous Chalcogenide Semiconduc- tors (VCS) for high resolution recording of the integrated elements. The processes of selective chemical etching of VCS layers are investigated both of the exposure conditions and parameter of etching solution.
Adiabatical quarter wave plate
Author(s):
M. Ya. Darscht
Show Abstract
The possibility of adiabatical conversion of circular polarized light into linear polarized one is considered for the case of the medium with both optical activity and inhomogeneous birefringence.
Equipment for real time MTF testing of copier and fax lenses
Author(s):
Hyun Mo Cho
Show Abstract
This paper describes the fabrication and performance of a testing system for copier and fax lenses in mass production. With the crossed line objects and 2-dim CCD arrays, we could measure the radial and tangential MTF in on-axis and off-axis at the same time. The MTF characteristics of copier and fax lenses measured by this equipment show different results according to the direction of the charge coupled shift register, shutter speed and the amplifier gain of CCDs. This equipment is calibrated by using standard lenses.
New mobile scanning aerosol-ozone lidar maket-2
Author(s):
Hyun Mo Cho
Show Abstract
The lidar is a good tool for investigations of atmospheric aerosol and ozone due to its possibility to give a continuity of measurements, to its easy handling and to its low cost[1]. Now Mobile scanning lidars are in use for multispectral and polarization measurements[2,31. To investigate the formation and life cycle, height, thikness and optical parameters of contrails the Fraunhofer Institute for Atmospheric Environmental Research has built a mobile scanning lidar employing a Nd:Yag laser(1064, 532 and 355 nm) and 52 cm cassegrain telescope for depolarization and multiwavelength backscattering measurements[1]. The lidar is accommodated in a 20 feet container for the sake of mobility. A similar mobile lidar (optical receiver 30cm) was built in the Meteorological Institute of the University of Munich for monitoring the spatial distribution and temporal evolution of cloud fields and aerosol layers[3].
Grin optics, Fourier optics and optical connections
Author(s):
C. Gomez-Reino
Show Abstract
GRadient-INdex optics is an active area of research in optical communications. The goal of this paper is to give an overview of GRIN optics and its applications in optical connections.
Improving soliton transmission by filters and optical phase conjugation
Author(s):
Sien Chi
Show Abstract
Reductions of the soliton interactions by using the optical sliding-frequency filters and optical phase conjugation are numerically studied. For the filters, the second-order Butterworth filters can more effectively reduce the soliton interactions than the Fabry- Perot filters or the third-order Butterworth filters, and the zigzag-sliding case is better than the up-sliding or the down-sliding cases. It is shown that, by properly applying the conjugators and choosing the filter bandwidth, the soliton transmission can be significantly improved.
Optical surface topography measurements and characterization
Author(s):
H. J. Tiziani
Show Abstract
For surface topography measurement and characterization it is necessary to calibrate the measuring devices. For comparison of measurements using different techniques it is important to specify the spatial frequency range of the microstructure. Two new methods for the measurements of surface shape and microstructure will be described; namely a confocal technique based on microlens arrays and an interferometrical technique based on heterodyne interferometry.
Imaging with reflection near-field optical microscope in light of evanescent dipole radiation
Author(s):
Mufei Xiao
Show Abstract
A theory to decompose the propagating waves and the evanescent field in the optical dipole radiation is applied to analyze the reflection near-field optical microscopy. It is theoretically and numerically demonstrated that a local field vertically polarized toward the sample surface at the very end of the probe will provide a longer evanescent field tail into the gap between the probe and the sample and, hence, will improve the imaging quality of the microscope.
Assembly and adjustment of a lithographic lens
Author(s):
U. Kruger
Show Abstract
The imaging performance of projection lenses is strongly influenced by the used tools and procedures of assembly and adjustment. This paper presents the experience we have, using the example of a wide-field g-line lens.
LC vision for the materials testing
Author(s):
M. G. Tomilin
Show Abstract
A thin layer of a homogeneously oriented nematic liquid crystal (NLC) can be used as an unusual recording medium for the materials testing in order to visualize the distribution of the weak power physical fields, local modifications and microrelef defects on the surface, and the structural inhomogeneities in the bulk. The initial NLC molecular ordering represents the basis for the external fields visualization. The ordering may be disturbed locally under the influence of the thermal, electric, or magnetic fields, molecular interactions, or electromagnetic irradiation. The recording of these areas becomes possible if the NLC deformed structure is illuminated in the transition or reflection mode, and the interference pattern to appear is studied in the crossed polarizers in comparison with the background structure [1]. The light intensity over NLC layer I(x,y) modulated by the defovried structure is described by the equation I(x,y) = Io sin4[6(x,y)/2], where phase delay o = f(n, nd, ne, no, H); n, nd are the refractive indices of a nondeformed and deformed NLC layers; no, ne are the refractive indices of the NLC layer for the ordinary and extraordinary polarizations, H - the NLC layer thickness.
Substrate mode hologram for high efficient aberration-free coupling between collimated and uncollimated beams
Author(s):
Pavel Cheben
Show Abstract
The substrate mode hologram (SMH) design for high efficient and aberration-free direct coupling (in absence of the collimating optics) between collimated and uncollimated beams via totally internally reflected (TIR) beam is presented. Some experimental results are submitted for one particular geometry (plane wave - to - divergent Gaussian wave coupling via substrate; the coupling efficiency 58 %). The proposed method can be implemented in design and fabrication of the holographic optical interconnectors based on the substrate mode holograms.
Image reproduction of Bragg gratings
Author(s):
Hyun R. Lee
Show Abstract
A technique is described that precisely controls the spectral resonance wavelength of Bragg grating before they are written onto an optical fiber. The Bragg reflector filters can then be produced at any desired wavelengths.
A calibration method of the system error used for CCD MTF measurement
Author(s):
Changyuan Han
Show Abstract
A specific equipment for testing the CCDs has been built in our institute. The schematic diagram is shown in Fig. 1 . A 40A microscope objective with long working distance of 2.5mm is used for observing and adjusting the array elements of the undertest CCD. The CCD and its driving circuits are mounted in a CCD box that is fixed on the table which can be adjusted precisely on five dimensions. Along the CCD array direction the table can move about 100mm. The precision slide used for this displacement has the straightness of 1 arc second. The distance of the displacement is measured by a heterodyne laser interferometer with the accuracy of 0.1µm.
Design of quasioptical diffractive millimeter wave antenna
Author(s):
Zhenwu Lu
Show Abstract
Based on scalar diffraction theory, a new type of millimeter wave antenna--quasioptical diffractive antenna is designed and manufactured. The design theory and space shadow are discussed in details, and the calculated and measured results are presented. The results show that the diffractive antenna has good properties.
Plasma ion assisted deposition: a novel technique for the production of optical coatings
Author(s):
K. Matl
Show Abstract
Ion assisted deposition (IAD) is a well known technique to improve the properties of thermally evaporated thin films. A wide range of materials and completed layer systems have already been investigated. Because of the low total ion current and the small beam size of the commercial available ion sources, the useful substrate area is strongly limited. With a newly developed advanced plasma source (APS) we have overcome these problems. A total ion current of up to 5 A with excellent uniformity over a large area substrate holder ( 1 m2) has been achieved. The plasma source is installed in conventional box coating systems. Besides plasma-IAD the APS is also useful for plasma- CVD processes like plasma polymerization. The principle of operation of the plasma assisted processes with the APS is described. Results of dielectric materials and completed layer systems like shift free line filters, ITO-coatings and AR-coatings are presented. In particular, in case of organic substrate materials, the advantages of the APS are outstanding. Scratch resistant layers in combination with AR-coatings and hydrophobic surface layers onto organic substrates are successfully introduced in production.
Three-dimensional microfabrication with two-photon absorbed photopolymerization
Author(s):
Shoji Maruo
Show Abstract
Fabrication technology for three-dimensional microstructures with submicrometer accuracy has been needed in the fields of modern optics, such as micro mechanical system driven with photon pressure[1, 2] and laser-trapping near-filed optical microscopy[3]. However, the present accuracy with stereolithography[4] is not yet satisfactory to this purpose. Moreover, it is not so flexible to make a three- dimensional structure with the present technique. In this paper, we propose a new microfabrication method in which a point in three-dimensional volume of UV photopolymerizing resin is photopolymerized through two-photon absorption process. The microfabrication with two-photon absorption drastically improves the depth resolution due to a nonlinearlity between the power of the irradiation and that of the absorption[5].
Advanced concepts of laser beam integration by beamlet shaping
Author(s):
E. W. Kreutz
Show Abstract
Many applications of micromachining with laser radiation require homogenous illumination of a mask or a workpiece or even illumination by a process adapted power density distribution. Especially, in laser structuring of surfaces e. g. photolithography or ablation the power density distribution significantly influences the processing result. Thus, process adapted beam shaping becomes an important task for the optimization of the beam delivery system. The most prominent problem especially for mask imaging with UV laser radiation is the generation of power density distributions, which are adapted to the mask geometry in order to improve the processing efficiency considerably. No satisfactory concepts exist for the generation of arbitrary processing adapted power density distributions. Beam shaping with conventional holographic devices shows a pronounced dependence of the resulting distribution on energy fluence and phase distribution of the incident beam. Thus, a sufficient quality of the processing result cannot be assured. The analysis for the performance of the beam shaping by multifaceted imaging and non-imaging integrators with respect to the statistical properties of the incident laser radiation is reported using advanced beam shaping [1].
Deposition and analysis of carbon and silicon clusters generated by laser-induced gas phase reaction
Author(s):
M. Ehbreht
Show Abstract
Laser driven gas-phase synthesis in a flow reactor was employed for the production of carbon and silicon cluster beams starting from gaseous compounds. It is based on a CO2-laser-induced decomposition of molecular gases containing carbon and silicon, such as C2H2 and SiH4. By introducing a skimmer into the reaction zone, the generated clusters are transferred to the free molecular flow and analyzed with a time-of-flight mass spectrometer. These clusters were deposited on a silicon or saphire target at room temperature. Micro-Raman spectroscopy techniques was used for- characterization of this deposits. The present studies show that the laser-driven nucleation in a flow reactor is a powerful technique to produce fullerenes and silicon quantum dots and other nano-size semiconductors or high-temperature evaporated materials.
Photo-isomerization dynamics of isolated and surface-adsorbed stilbene molecule: comparative study
Author(s):
Raimo Silvennoinen
Show Abstract
A clear understanding of dynamics of conjugated it-systems on the surface provides a fundamental theoretical basis for the design of photochromic materials, organic conduc- tors, and nano-switches centers. The present paper is focused on a detailed examination of the excited state dynamics of stilbene molecule, both isolated in the gas phase and physisorbed on an inert surface. By obtaining a fundamental understanding of the pro- cesses this molecule can undergo in both environments, we hope to gain insight into not only how desired isomerization channels in the case 7-systems might be enhanced and controlled, but also how a surface can influence a photoisomerization process.
Measuring complex index and surface profile through phase-shifting interferometric techniques and maximum-likelihood estimation theory
Author(s):
Eric W. Rogala
Show Abstract
A novel interferometer based upon a conventional phase-shifting design is presented. The aim is to introduce the capability of measuring both the surface profile and the complex index of refraction of the test surface. Maximum-likelihood estimation theory and Cramer-Rao lower bounds are introduced and shown to be an effective means of extracting the complex index and surface profile parameters from the measured data and quantitatively assessing the performance. As the design parameters are optimized, the results are shown to improve and approach the theoretical performance limit.
Non-destructive contactless tool for semiconductor wafer inspection
Author(s):
O. V. Astafiev
Show Abstract
A method for semiconductors investigation and technological inspection are represented. It's optical non-destructive contactless and expressive tool. There are two general ways for the method applications. The first one is detection of inhomogeneities for free carrier distribution in bulk of semiconductor, which occur due to electrically active defect. The second one is direct visualization of recombination picture on surface of semiconductor wafer (in over words, it's lifetimes mapping).
An intelligent system for the measurement of surface microstructure
Author(s):
Zhihua Ding
Show Abstract
We have developed an intelligent surface profilometry, with vertical resolution of 0.3nm, lateral resolution of 0.93 μm and testing accuracy of 0.5nm. This system can provide not only 2-D and 3-D topographies of testing surface, but also different evaluation parameters of surface roughness. In our system a feedback-control is implemented for phase shifting, and therefore problems encountered in the piezoelectric transducer are overcome. Comments on interferometer design and experimental examples are given in our paper.
Optical Gabor transform in surface reconstruction
Author(s):
Michael Friedmann
Show Abstract
For an experiment in which a surface is scanned by a coherent beam and the scattered far field is measured, the correct mathematical tools are provided by the Gabor transform formalism. This work describes a method that uses this approach together with a parallel POCS algorithm, to reconstruct surface features. The method shows how to reconstruct a phase only object from amplitude-only data measured in a scanning experiment. An improvement of the method permits to recover frequencies lost due to the finite aperture of the optical setup.
Characterization of silica-based waveguide layers for integrated optics application
Author(s):
Hyung Jong Lee
Show Abstract
Sensitive and simple methods to examine the quality of waveguide layers, such as in-plane scattering method and laser beam scattering method, are newly introduced. We apply this methods to evaluate the silica-based CVD and FHD waveguides layers and compare these methods with others such as the stylus scan measurement of the surface, the interferometric test of waveguide layer, and the measurement of propagation loss. The Fl-ID waveguide generally shows higher loss with more surface waviness than the CVD waveguide, which comes from the different nature of the FHD process. The quality of the best optimized FHD wafer aproaches that of the CVD wafer, but depends highly on the process condition.
New type of auto oscillations under the interaction of laser radiation with an absorbing liquid
Author(s):
Andrey V. Levin
Show Abstract
New type of auto oscillations during the interaction of cw laser radiation with absorbing liquid was examined. It is noted that the oscillations do not originate from laser beam transformation by the material vapor jet. The conditions of existence of auto oscillations were investigated experimentally. It was shown that the heating of interaction zone to the boiling point of the liquid was necessary for the oscillations observation. Modeling of the process was carried out. The qualitative agreement with the experimental results was obtained.
Measurement of grain boundary sliding in copper by two-beam interferometry
Author(s):
A. Ayensu
Show Abstract
A two-beam interferometry has been used to determine the extent of grain boundary sliding contribution to total creep deformation in polycrystalline copper. The sliding strain was evaluated from the relationship, egbδ (%) - Φv̄/d, where Φ is geometrical factor, v̄ is mean vertical offset and d is grain size.
Measuring small angle with Talbot effective
Author(s):
Cheng Wang
Show Abstract
A novel method to measure a small angle of optical ray with Talbot image combined with moire technology. The accuracy of the method will reach the 0.04", if we use this method with the opticelectron elements as a receptor.
Method for defect selection in grinding sapphire wafers
Author(s):
O. V. Astafiev
Show Abstract
It is known that inexpensive sapphire produced by means of Verneuil growth method contains special type of defects. The defects are accumulations of micron scale bubbles that occur due to growth process. General consumer of the sapphire is watch industry, which demand for the material is quickly increased for last time. It's very important to select the defects before stage of fine polishing. We represent a new technique for selection defective sapphire wafers with grinding surfaces. The technique is non-destructive, contactless and expressive tool for technological inspection.
Diffractive optics produced by holography and RIE
Author(s):
Lucila Cescato
Show Abstract
New diffractive optical elements were performed by holographic exposition of photoresist masks and reactive ion etching of the substrates. In particular we report the project and fabrication of a diffractive element which splits the incident unpolarized light its two orthogonal polarizations by reflection.
A CMOS-compatible pin photodiode with variable photosensitivity for optical interconnection
Author(s):
Jung Woo Park
Show Abstract
For optical interconnection application, typically GaAs light source or Si photodiodes are employed. For the receiver electronics, however, the CMOS technology would be the technology of choice for both the performance and the cost. In this paper, we present a photodetector technology that is completely CMOS compatible and has a novel structure that leads to variable photosensitivity. The latter can be used for both optical switching and logic applications as well.
Integral poly-Gaussian model for non-Gaussian rough surfaces
Author(s):
Michael Ya. Litvak
Show Abstract
A new statistical model for non-gaussian stationary random processes and fields is proposed. The distinctive feature of the model is that the probability distributions of all orders have the form of integral polygaussian mixtures. The model can be applied for the description and computer simulation of one- and two-dimensional rough textures as well as for theoretical studies of interaction of light or particle flows with non-gaussian roughness.
New conception in microoptics aspherisation: laser shaping and polishing
Author(s):
V. P. Veiko
Show Abstract
A new laser method and apparatus for aspherisation of optical surfaces are described. The physical model of laser action on glass including laser shaping and laser polishing are discussed. The principals of design of laser installation for aspherisation of mini- and microoptical components are given. Some type of aspherical components like cylindrical lenses with hyperbolic and elliptic surface are produced, tested and presented.
Optical properties of SiOxNy thin films prepared by ion beam assisted deposition
Author(s):
Hyun Ju Cho
Show Abstract
Silicon oxynitride thin films were made by reactive ion beam assisted deposition. The refractive index of deposited films, determined by both envelope method and prism coupling method, was able to be varied from 1.46 of SiO2 to 1.97 of Si3N4 by controlling the stoichimetry. The packing density of silicon oxyniteride films was measured by the vacuum-to-air spectral shift and water absorption band.
Efficiency of transmission inclined surface-relief holographic gratings for backplane interconnects
Author(s):
M. Miler
Show Abstract
Holographic transmission grating couplers with an inclined surface relief, which are destined for backplane interconnects, were fabricated and their diffraction efficiency was measured during step-by-step development process. The highest efficiency achieved was obtained for p-polarized light which propagates inside a medium of lower optical density and is outcoupled into a medium of higher optical density.
Speckle smoothing using polarization control plate made of liquid crystal
Author(s):
Keiichi Sueda
Show Abstract
In the direct drive laser fusion, the smoothness of the intensity distribution of illuminating beam has been improved by the use of the random phase plate (RPP). A laser beam through the RPP is divided into many small beamlets and then piled up at a target plane with a focusing lens. The RPP reduces the nonuniformity of spatial phase and intensity distributions in a far field. However, the intensity distribution in a far field region consists of fully developed speckles due to random interference. Such fine structures cause an imprinting on the target surface, although the intensity envelope is relatively uniform. Therefore, we are investigating the polarization control for the instantaneous speckle smoothing to overcome this problems[1].
80 picosecond scanning optical delay line by using a helicoid-shaped reflective mirror
Author(s):
Chi-Luen Wang
Show Abstract
We have designed and developed a 80 ps scanning optical delay line by using a novel helicoid-shaped reflective mirror. By using the mirror, a quasi-real-time scanning autocorrelator was demonstrated to measure a 1.7 ps optical pulse by spinning the helicoid mirror. The time delay was linear proportional to the spinning angle of the mirror. The resolution and the maximum scanning range were limited by the beam spot-size and the pitch distance.
Analysis of ultimate transmission capacity of optical communication systems
Author(s):
Wei Wang
Show Abstract
The ultimate transmission capacity of the optical communication system, which employs a pair of non-zero dispersion-flattened fibers (DF-DSF) with opposite dispersion signs fabricated by ourselves, is analyzed. The system design is proved to be superior in future optical communication schemes.
Optical manipulation of microparticles using diffractive optical elements
Author(s):
Yoshio Hayasaki
Show Abstract
Optical trapping is a technique for the manipulation of micrometer-ordered particles, and has features of noncontact and nondestractivity, which are inherently features of the lights1, 2). The optical trapping technique was first demonstrated by Ashkin et al.1) in 1970. The technique has been initially used to manipulate biological cells and measure motor force of molecules in biological physics3,4). Recently, it has been used to extract the internal solution from trapped microcapsels by laser ablation in micorchemistory5) and to position and move micro-objects for micromachining6).
In situ monitoring of surface oxidation by laser speckle correlation
Author(s):
M. Muramatsu
Show Abstract
Despite the fact that oxidation processes have been studied for a long time, there are still difficulties in knowing what happens in the initial stages of the oxide film formation over non-optical (i.e.rough) surfaces. That is partly due to the lack of sensitivity of present methods, namely the quartz microbalance and the measurement of electrochemical potential, for detecting the presence of very thin layers of oxide [1,2]. Other existing methods are either unsuitable for in-situ measurements [3] or need polished surfaces [4]. The study of the initial oxidation stages can be of utmost importance given the fact that in many situations most of the oxide film forms in the very first moments of the reaction [5].
Soliton propagation in a system with bandwidth-limited and nonlinear gain
Author(s):
Mário F. S. Ferreira
Show Abstract
The propagation of a nonresonant optical soliton in the presence of spectral filtering, linear, and nonlinear gain is investigated. By keeping the filtering fixed, we show that the steady-state soliton amplitude diverges as the linear gain vanishes. We also show that the nonlinear gain only reduces but does not suppress the instability due to the background linear waves. This instability can be suppressed by considering the saturation of the nonlinear gain, while it is accentuated by the detuning of the soliton from the gain peak frequency.
Experiment-theory agreement for light scattering by a cylinder on a substrate including burying effects
Author(s):
J. M. Saiz
Show Abstract
Experimental results of light scattered by metallic circular cylinders on flat substrates are compared with those obtained from numerical calculations via the Extinction Theorem of the Physical Optics. Cylinder diameters of 1.1 μm and 20 μm, illuminated by an incident wavelength of 0.633 μm and 10.6 μm respectively, have been used. The effect in the scattering patterns of partially embedded cylinders is also taken into account.
Water absorption on the polished stainless steel surface studied by ellipsometry
Author(s):
Hyunsoo Nham
Show Abstract
A photoelastic modulation (PEM) ellipsometry is employed to study a water adsorption on SUS 310 surface in air as a function of relative humidity change. A natural evaporation type humidity generation method and a divided-flow type humidity generator is used to control the humidity in a chamber in room temperature condition. Detected signal shows strong ties to room temperature fluctuations and drift of optical properties of ellipsometric components including light source. Under even such a rough environment, adsorption occured and optical response is detected as relative humidity changes.
Optical microlithographic phase-shifting mask technology
Author(s):
Boru Feng
Show Abstract
In the paper, described systematically are the primary principles, computer simulation and photolithographic exposure experiments of phase-shifting mask (PSM) technology. The results of PSM computer simulation and exposure are given. The research shows that with PSMs resolution and process latitude can not be markedly improved unless some critical parameter requirements are satisfied. By use of a 10 × reduction g-line step-and-repeat stepper and chromeless PSM, clear photoresist patterns of 0.2 μm are achived. It is also shown that PSM technology has the excellent properties in resolution improvement, extending lifetime of optical microlithography and further developing the photolithography resolution limit.
Spectral correlations in white light scattering by non-Gaussian rough surfaces
Author(s):
Michael Ya. Litvak
Show Abstract
A new approach is proposed for calculation of the intensity autocorrelation function in spectrum of white light scattering by a phase diffuser with an arbitrary distributed rough surface. Results of the calculations for gamma-distributed diffusers and integral polygaussian surfaces are presented. It is shown that in the absence of the coherent scattering the spectral correlation for non-gaussian diffusers isn't completely defined by the first-order height. distribution but depends also on the type of the surface autocorrelation and the statistical model of the roughness.
Layer-by-layer digital reconstruction of 3D field by electronic holography
Author(s):
Zhiqi Hao
Show Abstract
In this paper, a quantitative layer-by-layer analysis method of 3D field is described. Using electronic holography method, realized the layer-by-layer reconstruction of the hologram which recorded the real 3D object field. It includes 1)digital recording of hologram, 2)numerical reconstruction of the complex amplitude on hologram plane, 3)calculating of the intensity on other plane paralleled to hologram surface by diffraction formula in the spatial frequency domain. According these, the reconstructed images on any plane of 3D field can be obtained. And finally the layer-by-layer reconstruction results of a real 3D field are shown.
Optical evaluation of the fractality of rough surfaces using array illumination
Author(s):
Naoya Wada
Show Abstract
In general, the most suitable characterization of rough surfaces has been given by the physical quantity of roughness. In recent years, however, it has become clear that a certain class of actual surfaces has complicated structures with scale-invariant features and is not effectively characterized only by the roughness since such structures do not have characteristic lengths [1]. The rough surfaces with scale-invariant features are called fractal surfaces.
Laser confocal microscopy study of impacts from a CO2 industrial laser to select optimal modal distribution
Author(s):
M. F. Creus
Show Abstract
Surface impacts on carbon steel were performed by using a computarized CO2 laser. The distribution of the incident beam was analysed by its effects onto the surface of samples. Laser confocal microscopy (LCM) was used in the optical tomography mode to study the thermal affected areas of the impacts. The aim of this work is to make a quantitative appreciation of the modes present in the laser beam to shape them by numerical control for specific applications, being cutting and hardening the more interested processes.
Corrosion resistance of laser cut hipoeutectoid carbon steels
Author(s):
Guillermo A. M. Alvarez
Show Abstract
Samples of low carbon steel with different C contents were cut with an industrial laser with power emission from 200 to 2000 Watt in CW regime. Samples were then submited to corrosive natural and laboratory environments. Atmospheric corrosion and inmersion tests were followed by SEM-EDAX analysis to determine relative activity of laser affected and non affected zones. We were able to distinguish two different affected zones and one non affected zone. Electrochemical behaviour of the zones were determined by potentiokinetic polarisation and the morphology of the attacks were compared through SEM to those naturally nucleated in the distinct environmental conditions. The corrosion resistance and surface hardness increases determined, were associated to the structural changes caused by the laser thermal modification of the kerf walls. We infer that the susceptibility of these steels to exfolliation in marine environments can then be reduced by laser heat treatments.
Optical image transmission through an optical fiber by spectral coding
Author(s):
V. I. Bobrinev
Show Abstract
One way parallel image transmission through the multi-mode optical fiber was realized by the spectral coding method. Multistripe holographic gratings were used for direct transmission of 10 × 20 pixel two dimensional images. It was done by decomposing light from point source in a two dimensional spectrum, each wavelength corresponding to one image pixel.
Profilometry of a plane reflecting surface using a confocal scanning optical microscope
Author(s):
D. M. Gale
Show Abstract
Numerical studies of the performance of a one-dimensional Confocal Scanning Optical Microscope (CSOM) used as a profiler of highly reflecting surfaces have shown that the microscope suffers a degradation in performance for surfaces with high slope or discontinuities. These studies have serious implications for the use of the CSOM as a non-contact surface profiler. We will present an experimental study of the response of a CSOM to simple plane reflecting surfaces with varying degrees of tilt, with emphasis on the depth discrimination property and the ability of the instrument to accurately profile such objects.
Optical computer tomography as a tool for nondestructive inspection and testing
Author(s):
S. Yu. Berezhna
Show Abstract
A New experimental technique and its application in an optical computer tomography of tensor fields are reported. Decision of the tomography inverse problem is suggested to be carried out with utilization of a cell model and a Jones-matrix calculus. A special polarimetry technique that was invented for an automatic whole-field measurement of a set of normalized Jones-matrices is briefly described.
Transmission properties of a multilayer polarizer filter realized with quasiperiodic code
Author(s):
M. Bertolotti
Show Abstract
In recent years there have been many theoretical studies of one-dimensional (1D) quasi periodic structures realizing Fibonacci sequences [1,3] or Cantor sequence, obtained by alternating layers of GaAs and AlAs. The interesting properties of the structures studied in papers [1-3], are linked to the properties of self-similar spaces. A self-similar space is characterized by three kinds of dimensions: the dimension of the embedding Euclidean space, the fractal and the spectral (fracton) ones [4].
Wavefront correction of laser beam using a deformable mirror with a large aperture
Author(s):
G. Y. Yoon
Show Abstract
Wavefront distortion of a laser beam is generated by the static wavefront aberration included in optical devices and the dynamic source such as convective disturbance for laser beam propagation, the change of a refractive index by thermal absorption in a laser medium and nonlinear effects in a resonator. These wavefront distortions cause deteriorating the performance of a laser system. Adaptive optical system (AOS) which consists of a wavefront sensor and a wavefront correction device (deformable mirror) can solve this problem. Particularly, for a high power and high repetition laser system for the purpose of laser fusion and laser processing, AOS may be effective.
Remote node for uni-directional self-healing ring network
Author(s):
S. Y. Park
Show Abstract
We propose an architecture of remote node for uni-directional self-healing ring network and formulate an inter-channel gain deviation of ring network resulting from nonuniform gain of erbium-doped fiber amplifier when arbitrary fiber span is cut.
Examination of photodoping phenomenon by in-situ ellipsometric observation
Author(s):
J. Lee
Show Abstract
Phenomenon due to Ag photodoping into amorphous As2S3 was examined with an ellipsometric method. Obtained values of ellipsometric parameters Ψ and ∆ were fitted by using multilayer model. It was found that each thickness of Ag, Ag:As2S3 and As2S3 layers showed a time dependent change during the diffusion process in photodoping and the optical constants of As2S3 change remarkably by Ag photodoping. These behaviors were explained in relation with photodoping mechanism.
Waveguiding properties of As2S3 optical waveguide doped with Ag by photodoping technique
Author(s):
Tsutomu Ogawa
Show Abstract
Amorphous As2S3 shows a remarkable volume expansion and an increase of refractive index by the diffusion of Ag. The feasibilty of application of Ag photodoping effect to the fabrication of micro optical elements in an As2S3 waveguide was investigated. It was found that a small Ag doped area and a small amount of Ag doping had large effects on waveguiding properties.
Fabrication of infrared interferometer and its application for characterization of Ge
Author(s):
Moriaki Wakaki
Show Abstract
A Fizeau type infrared(IR) interferometer was fabricated and its performance was characterized using a Ge and other infrared materials. A IR He-Ne laser(wavelength of 3.39micron) was used as a coherent light source and an infrared imaging camera system was used for data acquision and processing. An annealing effect of single crystal, polycrystal and cast grown Ge was investigated using the interferometer. IR transmission images of Ge were also observed using a black-body source and IR camera.
Spin-orbit interaction of a photon: mutual influence of polarization and propagation
Author(s):
N. B. Baranova
Show Abstract
Several effects of classical linear optics were predicted and observed experimentally. The report will contain the description of the experiments and of the related electrodynamic theory. General statement is that the geometric-optical description of the polarizational effects works at much larger distance, than the same description of the rays and transverse patterns of intensity.
Theory of self-focusing media, GRIN and holographic elements
Author(s):
A. L. Mikaelian
Show Abstract
Problems of wavefront transformation by means of optically inhomogeneous media and holographic elements are considered. Both approaches use a theory that is based on solution of electrodynamics reverse problems. Examples of SELFOCs, GRIN lenses, and holographic beamsplitters are given. The latter elements are fabricated by means of e-beam lithography.
Inverse scattering for rough surfaces
Author(s):
C. J. R. Sheppard
Show Abstract
Reconstruction of surface profiles from scattering data is considered in the Kirchhoff aproximation. For reconstruction of the profile phase information is required. For surfaces with Gaussian height variation, the autocorrelation function can be determined from intensity data.
Weak localization of light backscattered multiply from fractal media
Author(s):
Katsuhiro Ishii
Show Abstract
Intensity enhancement in the multiple scattering from highly disordered media is produced in the direction of retroreflection, and is called weak localization of light or enhanced backscattering1). It is well known for the scattering from uniform random media that the intensity peak decreases in inverse proportion to the backscattering angle2). However, it was experimentally shown that a decreasing behavior is broken for a random medium with a fractal structure produced by the aggregation of particles3). Due to the difficulty in controlling the fractal dimension of scattering media, there is no quantitative study on the enhanced backscattering produced from fractal media. In this report, we investigate quantitatively the dependence of the intensity peak on the fractal dimension (cluster dimension) by using Monte Carlo simulations.
Dynamic programming: an alternative approach to light propagation in arbitrary optical media
Author(s):
Maria L. Calvo
Show Abstract
We apply techniques of optimal control theory namely, the dynamic programming to the problem of light propagation in optical waveguides. The formulation is equivalent to the resolution of an eikonal equation. We illustrate this optimization technique for a gradient profile optical waveguide, i.e., an ideal parabolic refractive index profile distribution. We discuss the possibility of extending this procedure to other type of optical waveguides and optical media and implications in optical design.
Multiple scattering of light by red blood cells
Author(s):
A. G. Borovoi
Show Abstract
Distribution of red blood cells (RBC) over their sizes, shapes and the other internal structure parameters is one of the important diagnostic values that is helpful and perspective in medicine. Usually measurements of such distributions are made manually with a microscope and therefore these measurements prove to be time-consuming and subjective. A number of devices allowing to automatize these measurements are proposed where the devices using the laser light scattered by the RBC are of main importance.
Total absorption of light at uniaxial gratings
Author(s):
Miriam L. Gigli
Show Abstract
The interaction between light and surface-plasmon resonances in the corrugated interface between a uniaxial crystal and a metal is investigated theoretically. The analysis allows us to predict the existence of critical conditions for which total conversion between photons and surface plasmons may occur.
Experimental verification of a model for two-wave mixing with nonplanar waves in sillenites
Author(s):
A. Kiessling
Show Abstract
Photorefractive crystals have a considerable potential to be used in information processing [1]. Because of high recording sensitivities and good crystal qualities as well as availability the sillenite crystals like Bi12Si020 (BSO), Bi12Ti020 (BTO) and Bi12Ge020 (BGO) are promising materials in the field of real-time interferometry and image processing.
Self-imaging with finite effective apertures
Author(s):
Rafael Piestun
Show Abstract
General solutions and conditions are presented for paraxial waves exhibiting self-imaging. The waves have finite effective support and are not included in the class of self-imaging wave-fields described by Montgomery rings in the Fourier domain.
The conversion efficiency of photovoltaic converters with pulsed lasers
Author(s):
Kyong C. Woo
Show Abstract
The conversion efficiencies of photovoltaic converters(GaAs, Si) for a pulsed nitrogen-pumped dye laser, a pulsed flashlamp-pumped dye laser, a flashlamp-pumped Nd:YAG and quartz tunsten-halogen filament lamp was studied. The conversion efficiencies were measured for different wavelengths of pulsed dye laser to verify the optimum wavelength, 0.87 μm for GaAs and 1.13 μm for Si photovoltaic converter, expected from the bandgaps of the photovoltaic converters. A significant reduction of the conversion efficiency is noted compared with that of continuous wave laser and solar radiation.
Electron energy spectra states of cadmium and zinc diphosphides
Author(s):
I. Fekeshgazi
Show Abstract
Owing to felicitous combination of high efficiency of non-linear light absorption and optical activity on frequencies of solid state lasers emission the gyrotropic crystals of cadmium and zinc diphosphides became a model objects for study the effect of space dispersion on non-linear optical phenomena. As is generally know, the efficiency of non-linear light absorption is determined by a quantity of energy levels in forbidden gap and also by a number of valency and conductivity bands under of these the virtual or real two-quantum transitions are realized.
High resolution 3D laser interferometer with reduced linearity error
Author(s):
Bernhard Hils
Show Abstract
We describe an interferometer-system for simultaneously displacement and tilt measurement that satisfies present need of high accuracy and high resolution in the sub-nm and sub aresecond range. This accuracy mainly requires the determination and correction of three major error sources in optical interferometry: Abbe offset error, changes of the refractive index of air and cyclic errors in phase detection.
Polarization anisotropy in near-field intensity patterns scattered multiply from dense random media
Author(s):
T. Iwai
Show Abstract
Very impressive phenomena due to the multiple backscattering were experimentally observed in the lidar backscattering from atmospheric water droplet clouds1) and the backscatterings from the random surface with relatively large slope in the correlation area2) and the spherical particles suspended in the water3). In the near field, (1) the bow-tie intensity pattern is produced in the co-polarized component1), (2) the cloverleaf intensity pattern is produced in the cross-polarized component2,3), (3) the intensity pattern enlarges radically and its contrast increases with a decrease of the particle size3). These may be attributed to the memory effect of the polarization in multiple scatterings. In this report, the numerical investigations are conducted by using the Monte Carlo simulations on the basis of a phase function for the Rayleigh-Debye scattering theory since the resultant polarization effects depend substantially on the polarization properties of the individual scattering event from the single particle with a finite size.
Time-resolved measurements of the size and two-dimensional motion of small particles using an image sensor
Author(s):
Yasuhiro Harada
Show Abstract
An extended method is described for continuous measurements of the size and two-dimensional (2-D) motion of single spherical particles using an image sensor. It is based on two-fold principles: the formation of a streak image of the particle from light scattered into an off-axis forward direction and the scanning detection of the streak image by a 2-D MOS imager which employs the X-Y addressing format. Unlike conventional video camera methods, all time-resolved information of the particle size and motion can be determined by evaluating the intensity distribution of one frame image with an attainable time resolution of 63.5 μs.
Correlation requirements for displacement analysis by ESPI experimental and FEM analytical methods
Author(s):
R. Rodríguez-Vera
Show Abstract
This work describes the results of experimental and analytical studies conducted in a project to identify the requirements for correlation between experimental displacement measurement data and finite element analytical displacement estimation. The work attempts to define fundamental requirements for both test and analysis that would improve correlation potential. An in-plane sensitive Electronic Speckle Pattern Interferometer (ESPI) is the experimental method and a Finite Element Method (FEM) is the analytical one. The impact of proper experimental setup and instrument design, rigid body control, and loading problems are discussed. An assessment of the minimum FEM modeling details has also been provided.
Wigner distribution function of a circular light source
Author(s):
Martin J. Bastiaans
Show Abstract
The Wigner distribution function of a time-harmonic, uniform, circular light source is determined. Analytic expressions as well as numerical and graphical results are presented.
Evolution of the stokes parameters in optically anisotropic media
Author(s):
Christian Brosseau
Show Abstract
The purpose of this communication is to describe an analysis for studying the propagation of a partially polarized wave within an arbitrarily linear anisotropic medium. We consider quasimonochromatic light in the form of plane waves of infinite extent propagating along the direction characterized by the unit vector e3 which together with the directions e1 and e2 form an orthogonal set.
Phase stepping in digital grating-shear speckle pattern interferometry
Author(s):
Roberto Torroba
Show Abstract
A phase stepping technique for digital speckle pattern shear interferometer with the aid of a diffraction grating as shear element, is presented. In-plane translation of the grating introduces the required phase shift. Experimental results are presented to show the validity of the proposal.
Photonic interpretation of refractive index
Author(s):
Hassan Kaatuzian
Show Abstract
In this paper we'll introduce a new treatment called photonics -which is based on wave-particle nature of light- to estimate theortically the refractive index of a dense material in microscopic scales. The main result obtained from this research is the prediction of wave- particle unification! In stead of wave- particle Duality nature of light. The starting points in photonics are planck formula, Hamilton principle, Jacobi and Maupertuis' functions. We've successfully estimated microscopic delay parameter "τ", related directly to macroscopic parameter "n": The index of refraction.
Superslow optical relaxation induced by FM laser field in I2
Author(s):
Hui-Rong Xia
Show Abstract
The approaches to realize superslow relaxation receive growing attention for its correspondence to sharp optical resonance in frequency domain and to long term of information storage in time domain. Dephasing time as long as 2.6 mS was observed in the condensed matter of crystal under the temperature of 1.4K [1]. In RF ion trap Yb ion has been kept in its metastable excited state for 8 days [2]. Population trapping is one of the interested approaches recently. While most papers discussed it for Λ- or V-type three-level systems, Agarwarl et al has theoretically predicted the possibility of population trapping been established by frequency modulated laser field in two-level system [3]. The authors has demonstrated population trapping in high-lying state doublet and in intermediate state doublet via quantum interferences between two sum-frequency two-photon excitations in Y- and in rhomb-type four-level systems respectively [4].
Lateral vibrations measurement of powdery clay sample using speckle photography
Author(s):
P. K. Buah-Bassuah
Show Abstract
We report the use of lateral vibration of speckle patterns in studying the particle sizing of bulk powdery clay sample. A two-exposure recording was made on a high-resolution holographic plate placed in the observation plane. The first exposure was taken when the laser-speckles without the sample vibrated laterally and the second when the laser-speckles and the sample vibrated laterally together. The plate was photographically processed to obtain a specklegram. The analysis of the fringe pattern from the decoded specklegram gave the particle sizes in the sample.
Infrared vibrational modes and Raman scattering in CuAlS2, CuAlSe2, and CuAlxGa1-xSe2 crystals
Author(s):
A. M. Andriesh
Show Abstract
Reflectivity spectra of CuAlS
2, CuAlSe
2 and CuGaSe
2 crystals have been investigated in the wave number range 50 - 4000 cm
-1 for the polarization Εllc and Ε⊥c. The fundamental phonon parameters, the limiting dielectric constants ε
o and ε
∞ and the reflectivity spectra contours have been calculating by using classical dispersion relations for both Εllc and Ε⊥c configurations. The Szigeti effective charges and the relative ion charges of Cu, Ga, Al, S, Se anions and cations have been calculated in dependence on the incident light polarization.
Raman scattering of CuAlSe
2 (at resonance excitment), CuAlS
2 and CuAl
xGa
1-xSe
2 has been investigated at 300 and 77K. The modes caused by Al - Se and Ga - Se vibrations have been determined for CuAl
xGa
1-xSe
2 solid solutions. We have found that the intensity of the modes B
12(Γ3) - 107.2 and 210.5 cm
-1 increases whereas the intensity of Ε(Γ5) - 157.3 cm
-1 mode decreases as the exciting energy approaches the band gap Ε
g.
Far infrared optical study of CdInGaS4, HgInGaS4 and CdIn2S2Se2 crystals
Author(s):
N. N. Syrbu
Show Abstract
The infrared reflectivity spectra in the range from 50 to 4000cm-1 of the CdInGaS4, CdIn2S4, HgInGaS4 and CdIn2S2Se2 crystals have been investigated. The fundamental phonon parameters, the limiting dielectric constants εo and ε∞ and the reflectivity spectrum contours have been calculated using classical dispersion relations. The values of parameters obtained from the fitting procedure are listed in the table. It is shown, that the replacement of an anion (In by Ga) leads to appearance of additional vibrational mode caused by dynamics of Ga-S molecules.
Propagation-invariant electromagnetic fields
Author(s):
Z. Bouchal
Show Abstract
Some properties of the exact propagation-invariant solutions of the Maxwell equations are pointed out. Attention is focused on the transversality, energy flow and phase singularities of the stationary propagation-invariant electromagnetic fields.
Surface plasmons on nonlocal corrugated interface
Author(s):
Shu Wang
Show Abstract
We have studied the dispersion relation of surface plasmons on rough surfaces with spatially dispersive optical response. The theoretical work is based on the Rayleigh-Fano hypothesis, giving an exact solution of all amplitudes of the diffracted partial waves. One-dimensional roughness with TM polarization for the incident, reflected and transmitted light has been considered. The longitudinal mode has been included by using hydrodynamic dielectric function. We obtain our results from the resonance positions of the reflectivities for a corrugated vacuum-Ag interface and compare with the solution from the secular equation.
Dependence of spectrum changes on the ratio of coherence area to source area
Author(s):
H. Arimoto
Show Abstract
A change in optical spectrum is caused by both spatial coherence of a spectral source and dispersive diffraction by the source. The spectrum shifts toward higher or lower frequencies as a function of the ratio of coherence area to source area, depending on place to place in the observing location.
Stretched exponential growth of photoinduced defect population
Author(s):
K. Kim
Show Abstract
We show that the photoinduced defect population growth of a sample may have stretched exponential time dependence if the sample is optically dense and the defect does not decay nor diffuse within the time scale of the experiment. In this presentation, we will formulate and examine our model and low temperature photoinduced absorption and electron spin resonance of polyaniline will be described as an example.
Minimization of array generator for a Gaussian Schell-model beam
Author(s):
Hiroyuki Yoshimura
Show Abstract
Array generators are expected to realize in the field of optical multiplex communication system and optical parallel processing in the future. A source array is produced, when a light beam is incident on the array generator. We have proposed the array generator for a Gaussian Schell-model (GSM) beam and have investigated the properties of the resultant source array from the viewpoints of the average intensity and coherence
[1-3].
In the present study, we discuss the minimization of the array generator. Moreover, we compare the average intensity and coherence in the resultant source array with those obtained from the previous array generator.
Fractional cross-spectral density on a Gaussian Schell-model source
Author(s):
Hiroyuki Yoshimura
Show Abstract
Recently, an optical fractional Fourier transform (FRT) has been expected to apply to optical information processing. The FRT was first introduced by Namias in order to solve the harmonic-oscillator physical problem in quantum mechanics in 1980
[1]. McBride and Kerr improved the Namias's definition in 1987
[2]. In 1993, Ozaktas and Mendlovic introduced the optical FRT as the self-modes of a quadratic graded-index medium
[3]. Moreover, Lohmann pointed out that the FRT can be defined by an idea of the rotation of the Wigner distribution function (WDF)
[4].
In the present study, we introduce the fractional cross-spectral density (CSD), i.e., an idea of the FRT to the partially coherent optics. As an example, we theoretically analyze the CSD of the fractional optical field on a quasi-monochromatic Gaussian Schell-model (GSM) source.
About thin structure of speckle field
Author(s):
O. V. Angelsky
Show Abstract
The problem of vector theory of amplitude zeroes is discused.
M.Berry was the first who paid attension to the possibility of dislocation-like defects in electromagnetic fields
1. He showed under the scalar approximation, that different surprises can be wating for us even in rather simple sistems (including linear ones) that were traditionally studied, and rich variety of singular structures has been demonstrated. In Ref.
2, the complex amhlitude distribution of a monochromatic field is discussed, that obeys to the parabolic equation, in connection with the problem on the existance of points where the amplitude vanishes. It has been shown zero lines are any continous lines in 3-D space where the wavefront has the screw dislocation. Generation of wave-front defects was studied by numerous investigators, as well as the fine polarization structure of electromagnetic fields
3-7.
Input impedance from fractal multilayers
Author(s):
E. E. Sicre
Show Abstract
An impedance model is applied to the resolution of reflection problem by a multilayer Cantor bars fractal. We obtain an iterative method which consists in replacing the structure by a single surface.
The diffusion effects on the multilayer thin films
Author(s):
Yeong Sik Kim
Show Abstract
In fabricating optical thin films by evaporating dielectrics onto a glass substrate there are various unwanted errors for the structure of dielectric multilayers, for example, thickness errors, lack of thickness uniformity, anisotropic refractive indices of growing dielectric films in a certain direction, etc. In particular, it is of interest to take thermal diffusion into account in the process of alternate deposition of one low-index material and one high-index material. It is not possible to avoid the diffusion of thin films in vacuum deposition technology as long as the dielectric components of different refractive indices are to be thermally heated. It is the aim of this presentation to numerically determine the influence on the performance of the thin films from the thermal diffusion during the vacuum deposition inside a chamber system. It is required to solve the accurate equation[1,2] [see Eq.(2) below] for the reflection coefficients to find the performance of the thin films. In this presentation we confine ourselves to the thermal diffusion effects on the quarter-wave stacks of alternating two (high- and low-index) dielectric materials for high reflectance in a broad region and the filters which transmit only selected regions of spectrum. Here the dispersion has not been included in the calculations for simplicity.
Simple design to measure the scattering factor of laser mirrors
Author(s):
Om Prakash
Show Abstract
In order to characterise the laser mirrors, their scattering factor is a useful parameter in the present acticle is described a model of simple design to measure the scattering factor of the laser mirrors for the wavelength of laser radiation. The proposed model of the design is in the form of a dual beam ratio recording system, employing single detector and works on the principle of modulation radiometry In the design provision has been made to minimise the systematic errors such as effect of polarisation because of use of optical components, source fluctuations asymmetry in the paths of the sample and reference beams etc, occuring. during the measurements. The design is equally applicable to measure the scattering factor of the polished glass blanks of the laser mirrors.
Coherence filters and some of their uses
Author(s):
Tomohiro Shirai
Show Abstract
It has been predicted theoretically and verified experimentally that the spectrum of light radi- ated by a partially coherent source may change on propagation, even in free space. The change depends not only on the spectrum of the source but also on its spatial coherence properties [1]. Such correlation-induced spectral changes have become the subject of great interest in the last few years and have led to a new branch of optics, which is sometimes referred to as spatial- coherence spectroscopy.
Studies of infrared radiation characteristic spectrum on the igniting fire sources in wildland fire
Author(s):
Ning Mei
Show Abstract
The purpose of this study is to investigate the infrared radiation characteristic sp. ectrum from igniting fire in wildland lire.The infraredradiation spectrum and mean temperature in different characteristic fire region were measured at the same time.The results from two represen- tative kinds of igniting fire souces (cigarette and wood stick)show that the characteristic wavel- ength of the igniting fire distrbute from 1.1 um to 8.2 um,which are associated with the measured meantemperature in different combustion zone of the flame.The emissive power varies withwaveleng- th and is lower at shorter wavelength. Key words:infrared radiation spectrum, flame temperature, wildfire ,radiation from black body.
Space-time properties of the enhanced backscattering from highly disordered media
Author(s):
Katsuhiro Ishii
Show Abstract
The enhanced backscattering or weak localization of light in the laser light scattered multiply from highly disordered media has attracted a great deal of attention as a visual precursor of the Anderson localization. It is known that the constructive interference between the waves travelling along the time-forward and the time- reversed paths produces the intensity peak in the direction of retroreflection, depending on the polarization of scattering light, the particle size, the fraction of solution and so on' ). The remarkable spatial properties of the enhanced backscattering reflects on the temporal ones. It was experimentally shown that the temporal correlation function of backscattered light varies with the scattering angle depending on the polarization2'3). We investigate the dependence of the temporal correlation of the enhanced backscattered light on both the polarization of scattering light and the particle size of solution by considering its relation with the spatial properties. Investigations are conducted from the theoretical analysis based on the diffuse approximation, a Monte Calro simulation and an experiment. We demonstrate the remarkable spatial variation of the relaxation time depending on the direction of the polarization and the particle size.
Ramsey resonance characteristics of the optically pumped Cesium beam frequency standard at kriss
Author(s):
Ho Seong Lee
Show Abstract
We investigated Ramsey resonance characteristics of the optically pumped cesium beam frequency standard constructed at KRISS. The linewidth of the Ramsey signal from a 38-cm long microwave cavity was about 260 Hz. The linewidth and peak-to-valley values of the Ramsey signal versus the microwave power were observed and compared with theoretical results obtained by taking into account the 1/v-weighted Maxwell velocity distribution in the cesium atomic beam. Both results coincided quite well, but the asymmetry in the Ramsey signal occurred, the causes of which were discussed.
Interference effects of multiply-scattered light in strong scattering media
Author(s):
S. Sangu
Show Abstract
Volume multiple-scattering media induce large intensity fluctuations of 'the light which are similar to the "speckle patterns" due to single scattering from rough surfaces. These fluctuations are explained as a result of the in- terference between optical waves with random phase differences, and they usually obey the Rayleigh statistics. In case of the multiply- scattered light, however, the optical waves propagating through the same paths exist in a medium, and their interference effects mod- ify the properties of intensity fluctuations. Re- cently discovered phenomena, such as "en- hanced backscattering", "optical memory ef- fect" and "long-range intensity correlation" [1- 3], are caused by these interference effects. In a strong scattering regime, interference effects influence strongly the properties of the scat- tered intensity. In this paper, we present a numerical sim- ulation that takes account of interference ef- fects in multiple-scattering media, and evaluate the statistical properties of the scattered light across the output field(sample surface) and in the far-field.
Can one see an object better through a light-scattering medium as its optical thickness grows?
Author(s):
Vladimir V. Barun
Show Abstract
This paper considers some cases of increasing im- age contrast of an object with optical thickness of a turbid medium (e.g. atmosphere) through which one makes observations. The first one is related with viewing an isolated Lambertian ob- ject. The magnitude of image contrast is shown can increase under some conditions as the object is being submerged in the medium and can even have a maximum providing the best vision qual- ity. The second case examines observation of a non-Lambertian object against a background of a Lambertian surface. Increasing image contrast with a maximum is also possible here. This paper has given the mathematical description of the said effects that allows the imaging to be translated to rather simple analytical formulas.
Non-linear dynamics of laser intensity inside a Gaussian cavity
Author(s):
C. Palma
Show Abstract
Non-linear dynamics methods are used to study the build-up of a radiation beam in a laser cavity by analysing the behaviour of the beam intensity on optical axis. The dynamics is shown to have a fixed point, attained with characteristic behaviours, and it can be suitably modified to have a limit cycle.
The influence of photoelastic constants values on energy exchange of light beams in cubic photorefractive piezocrystals
Author(s):
V. V. Shepelevich
Show Abstract
The energy exchange of light beams in (110)-cut cubic photorefractive crystals at a different values of photoelastic parameters is investigated. It is shown that the change of photoelastic parameter p4 leads to the change of the relative intensity y of the wave S at the orientation angles 0 = 90° and 0 = 270° and at the polarization azimuth To=90°. At such angles 0 other photoelastic parameters do not influence on value of y but these parameters exert influence on value of y at other angles 0. The obtained results may be used for making more precise the photoelastic parameters values.
Scattering matrix approach to multilayer crossed gratings diffraction
Author(s):
Gérard Granet
Show Abstract
It has already been shown that the dif- ferential method of Chandezon is well suited for analysing multilayer diffraction gratings [1]. Lifeng Li has reported significant improvments to this method [2] . He used the R-matrix propagation algo- rithm to remove the limitation on the layer thickness and on the number of layers. As far as we are con- cerned, we have allowed for different interface pro- files within the grating structure although all must share the same periodicity [3]. Preist et al have done it also [4]. Boundary conditions were expressed with the scattering matrix approach which is an alterna- tive to the R-matrix approach. The aim of this paper is to analyze multi- layer crossed gratings with the Chandezon method and the S-matrix formulation. It consists of a genera- lization of the formalism already used for 2D multi- coated gratings. The basic features lies in the use of a coordinate system that maps the interface onto a plane. In the new frame, the structure is analogous to a planar stratified medium. As in the 2D case, we are led to a linear system of differential equations whose solution is obtained through the calculation of the ei- genvalues and eigenvectors of a matrix dependant on the geometry and on the index of the medium. As an example, we shall consider cases where "anomalies" in the diffracted efficiencies occur, that is when a suitable phase matching between the incident wave and the guided wave is achieved.
The polarization division of incident and reflected beams in optical disc systems
Author(s):
Michael I. Shribak
Show Abstract
In many systems with use of laser the incident beam when directed to an object is coincident in space with the reflected beam. This take place, for example, in a laser optical disc player. Separation of the reflected beam from the incident beam can be done by dividing them under of polarization with using of a polarization dividing unit. An example of the unit is shown in figure:
Fiber optic sensors based on birefringence fiber loop interferometer
Author(s):
E. A. Kuzin
Show Abstract
A high-birefringence polarimetric fiber sensor [1] typically includes a single mode polarization preserving fiber, an output polarizer and a detector. Two independent orthogonally polarized modes are propagating within the fiber and their phase difference may depend on pressure, temperature or other external parameters. The output polarizer converts this phase shift into the amplitude modulation measured by a photodetector.
Calibrating vertical magnification of surface roughness tester by using EMT and heterodyne laser interferometer
Author(s):
Chu-Shik Kang
Show Abstract
We developed a system which can calibrate the vertical magnification of surface roughness testers in the range of Itc, 0.1 ti 10 µm with high accuracy. The system consists of an electromechanical transducer(EMT) and a heterodyne laser interferometer. With voltage applied, EMT simulates a sinusoidal surface and heterodyne laser interferometer is used to measure the amplitude of the simulated surface. By calculating the theoretical roughness value for this surface, and dividing it by the measured roughness value, we can obtain the calibiation constant. With this calibration system, the relative uncertainty of calibration is 2%.
Fluorescence spectra of sol-gel glasses doped with organic molecules
Author(s):
M. A. Meneses-Nava
Show Abstract
The radiative characteristics of sol-gel glasses doped with quinine sulphate are investigated to study the effects of the porous matrix upon the absorption and fluorescence spectra. The broadening of the spectra is explained in terms of an inhomogeneous distribution of the adsorbed molecules into the porous glass. This inhomogencous distribution is produced by the attachment of the molecules to the substrate in a non-planar fashion or on distorted sites, for this reason each emitting center relaxes with its own characteristics.
Scattering in multilayers with shallow rough interfaces
Author(s):
Victor Monárrez Pérez
Show Abstract
Scattering at rough interfaces and guided modes in the bulk of a given layer are the cause of severe modifications in the optical performance of multilayer stacks, specially when some electromagnetic resonances occur, this is a typical case in alternate absorbing and transparent layers, where surface plasma waves may be excited. We present calculations of the scattered fields in the transmitted and reflected directions in a L-film system with shallow - rough interfaces that can be modelled as periodic, random or deterministic along the direction perpendicular to the incident plane beam. Because of the dimension of roughness we use the Rayleigh approximation and obtain a couple of integral equations to be solved numerically in a quasi-recursive way by using the input parameters, dielectric constants and thicknesses of all media, angle of incidence and wavelength. Some experimental results for the scattered reflected and transmitted fields for two and three films are presented and discussed here.
Spatial coherence control for illumination by use of liquid-crystal spatial phase-modulator
Author(s):
Kazuhiko Oka
Show Abstract
This paper presents a novel method for controlling the spatial coherence of illumination in an image-forming system. A liquid-crystal spatial phase-modulator is used for controlling it in the object plane. Spatial coherence of the light illuminating an object plays a critical role in determining the intensity distribution of an image or a diffraction pattern. From an experimental point of view, the development of excellent techniques for controlling the spatial coherence of illumination has been searched in the past. In this context, this paper reports on two-dimensional coherence control implemented by use of a liquid-crystal spatial phase- modulator (LCSPM). A scheme illustrating the working principle is shown in Fig. 1. A collimated beam of light from a laser source impinges upon LCSPM. A pair of arrayed transparent electrodes attached to its input and output faces are orthogonally arranged with each other, and the electrical potential across the electrodes are operated by the shift registers SR1 and SR2, respectively. Time-varying binary signals Vx(t) and Vy(t) are applied to SR1 and SR2, so that LCSPM can work with the space- and time-dependent electric signals. The applied electric signals cause a time-varying change in refractive index over LCSPM. As a result, the beam of laser light transmitted by LCSPM is phase-modulated in space and time. Since the output face of LCSPM is imaged over the object plane, the optical wave fields illuminating the object are controllable in spatial coherence. A twist-nematic liquid-crystal cell was available for LCSPM in the experiment. The two-dimensional spatial coherence control was examined with the help of a wave-front folded interferometer (see Fig. 2). This interferometer allows us to superimpose at the location of CCD TV camera the two optical waves that come from paired points
Enhanced backscattering of light by disordered media: effects of spatial coherence
Author(s):
Takashi Okamoto
Show Abstract
Coherent backscattering of light from random media has been studied intensively because of its relation to weak localization of photons [1]. Constructive interference of waves following a certain path and its time-reversed path in the medium yields an enhancement in the backscat- tered intensity. When the term "constructive interference" is used for the explanation of the origin of this enhancement, we implicitly as- sume that the light is perfectly coherent. Most of the studies relating to the coherent backscat- tering have been done under this assumption. In this paper we present an analytical ex- pression for a shape of the backscattering cone formed under illumination of the light with ar- bitrary spatial coherence. In a formulation, the statistical properties of the illuminating light is given by the angular correlation func- tion [2], which characterizes the correlation between two components of the angular spec- trum [3] of a light field. This plane-wave de- composition of the field allows us to make use of the analytical expressions [4] developed pre- viously for the coherent backscattering of scalar waves.
Holographic digital data storage systems
Author(s):
Lambertus Hesselink
Show Abstract
The performance of digital holographic data storage systems is rapidly improving as a result of better components and recording materials. In this invited paper we review state- of-the-art HDSS systems in terms of fundamental tradeoffs between materials and device characteristics. Recent results, including stored and retrieved video clips will be presented.
Applications of the fractional Fourier transform in optics and signal processing: a review
Author(s):
Haldun M. Ozaktas
Show Abstract
The fractional Fourier transform The fractional Fourier transform is a generalization of the common Fourier transform with an order parameter a. Mathematically, the ath order fractional Fourier transform is the ath power of the fractional Fourier transform operator. The a = 1st order fractional transform is the common Fourier transform. The a = 0th transform is the function itself. With the development of the fractional Fourier transform and related concepts, we see that the common frequency domain is merely a special case of a continuum of fractional domains, and arrive at a richer and more general theory of alternate signal representations, all of which are elegantly related to the notion of space-frequency distributions. Every property and application of the common Fourier transform becomes a special case of that for the fractional transform. In every area in which Fourier transforms and frequency domain concepts are used, there exists the potential for generalization and improvement by using the fractional transform.
Holographic memories
Author(s):
Demetri Psaltis
Show Abstract
Shift multiplexing is a method for holographic storage particularly suitable for holographic 3D disks. Holo- grams are recorded by interfering the signal beam with a spherical reference. In this paper we review the shift multiplexing mechanism and describe the design of a holographic 3D disk system that is capable of storing 12.4 bits/µm2.
Parallel processing with binary pupils
Author(s):
Jorge Ojeda-Castañeda
Show Abstract
We describe the use of simple binary masks for implementing multiple, local impulse responses. In this way a 1-D signal can be processed in parallel with several nonconventional operations, such as a Bessel function processor, or a fractional Hilbert transformation.
Perspectives for optical data processing and communication systems using optical thyristors
Author(s):
Hugo Thienpont
Show Abstract
The optical thyristor differential pair is a promising device for digital optical information processing. This bi- stable optoelectronic switch is usually implemented as a double-heterojunction PnpN structure in the GaAs/AlAs material system. In the off-state, it has a high impedance, while in the on-state, it is conductive and emits light perpendicularly to the surface with the emission characteristics of a LED. Recently experiments have been conducted by a joint research team of the Vrije Universiteit Brussel and the Interuniversity Micro- Electronics Centre (IMEC) to transmit information between adjacent pairs of thyristors on the same wafer, demonstrating cascadability. Transcription rates of 50 MHz at 7.2 fJoules optical input energy for an optical window area of 20 x 30 lim2 have been obtained [1]. The latest designs allow operation of the thyristor pairs at 3.3 V levels which makes it possible to integrate these devices with silicon VLSI circuits and to consider the development of smart pixel type elements with enhanced functionality.
Digital optical morphological image processing
Author(s):
Liren Liu
Show Abstract
This paper reports our developments on morphological image algebraic structures and corresponding cellular logic architectures suitable for optical parallel processing, and their optical compact implementations using stacked integrated techniques.
Limitations of hook method in measuring sputtered atomic density in a processing plasma
Author(s):
H. J. Kim
Show Abstract
The reliable measurement of plasma parameters such as sputtered atomic den- sity in processing plasmas is necessary to understand the fundamental physics of such plasmas and their relation to characteristics of deposited thin films. Hook interferometry is used to measure sputtered copper atomic density in a cylindrical sputtering magnetron discharge. Absolute densities have been successfully obtained as a function of radial position with small spatial density gradient. This paper will describe the application of Fourier transform techniques to analyse hook inter- ferograms and compare the limitations in measuring the atomic density with the conventional hook analysis method.
2D wavelet transform using the a multiplexing technique
Author(s):
Zeev Zalevsky
Show Abstract
The Wavelet transform is an useful tool for data compression, analyzing short transient pulses, optical correlators etc. A 2-D version of this transform was obtained optically using the multi-channel approach. In this project the Wavelet transform is obtained with a single channel. The information of the different scalings is transmitted in different wavelengths, and summed incoherently at the output plan. Laboratory experimental results are demonstrated.
The generalized temporal-spatial aligner distribution function and its properties
Author(s):
David Mendlovic
Show Abstract
The Wigner function is a powerful tool for analyzing signals and synthesizing systems. For one dimensional function, the Wigner domain is a two dimensional function that has two axes: the space/time axis and the temporal/spatial frequency axis. Basic optical elements as spatial lenses, time lenses, free space propagation, dispersive delay line and gratings, are expressed as known simple operations over the Wigner domain. In this project we generalize the Wigner function definition for handling both space and time degrees of freedom, together with spatial and temporal frequencies. The generalized representation is useful for handling spatial-temporal systems such as temporal optical processors and super- resolution.
Associative memory with spatio-temporal chaos control using partial Fourier information
Author(s):
Masanori Kushibe
Show Abstract
Control of spatio-temporal chaos in a neural net- work with discrete time and continuous state vari- ables is investigated. The chaos control is per- formed with the knowledge of only a partial Fourier information of the target in the memory patterns. The associative memory in a chaotic neural model is described and the result shows that the target pattern can be successfully associated with the pro- posed control algorithm.
Neural architecture for image halftoning
Author(s):
Thomas Tuttaß
Show Abstract
Neural structures may be used to describe halftoning methods, such as dither and IFTA and new binarization procedures based on layer networks can be created.
Logic control with a neural network
Author(s):
Masatomo Shirakawa
Show Abstract
A Hopfield neural network is capable of solving the optimization problems. We apply it as a cotrol unit to control a logical processing system and present the simulation result. Such a control has the advantages of flexible control of a processing system and reducing overhead in a parallel processing.
A neural network model for image compression
Author(s):
Wojciech Sygnowski
Show Abstract
In this paper a new method for image compression - the modified counter-propagation neural network algorithm which is a combination of the self-organizing map of Kohonen and the outstar structure of Grossberg is proposed.
Electro-optical correction of imaging properties by reconfigurable lens
Author(s):
Yasuhiro Takaki
Show Abstract
A reconfigurable lens, which is a tandem of a physical lens and a two-dimensional liquid crystal phase modulator, is controlled by an electro-optical system to correct degraded imaging properties. A computer iteratively changes a phase distribution of the modulator and evaluates an image to optimize the phase distribution, based on the simulated annealing algorithm. We demonstrate correction of imaging properties degraded by defocusing or phase objects inserted into an imaging system. The corrected imaging properties are even better than the original ones.
Optical flip-flop based on beam-fanning
Author(s):
Kanwal Kamra
Show Abstract
Photorefractive flip-flop consisting of two crystals placed in symmetric beam-fanning geometry is proposed. Beam-fanning under biasing illumination forms the principle of operation.
Bit-parallef strictly nonblocking selfrouting network: principle and optical architecture
Author(s):
V. B. Fyodorov
Show Abstract
The general principle of operation and 3-D architecture of NOT bit-parallel optically interconnected switching network with nonblocking and local path setting properties are proposed. The optoelectronic implementati- on of such networks from laser and photo- detector arrays, smart-pixel structures, free- space optics, and electronic units is considered.
Adaptive moving object tracking using nonlinear JTC
Author(s):
Yi-Mo Zhang
Show Abstract
In this paper an adaptive moving object tracking system using nonlinear joint transform correlator (JTC) as a main part is proposed . It shows good performance in tracking scale varying, rotation varying and shape varying object. Tracking principles and experimental results are given.
Joint transform correlator by subtracting phase-modified Fourier spectrums
Author(s):
Hongchen Zhai
Show Abstract
We report a new experimental solution for implementing joint transform correlator (JTC) by subtracting modified Fourier spectrum described in [1], in which the authors used an additional contrast-reversed reference to enhance the expected correlation peaks for binary image processing. In our new solution, there is only a phase difference between the two reference images, and the amplitude of them, however, remain the same. Besides, our solution is generally available for the optical processing with binary images as well as with images of multiple gray levels.
Interpolation approach to computer-generated holograms
Author(s):
Nobukazu Yoshikawa
Show Abstract
The interpolation method enables one to reduce the memory size and calculation times to fabricate computer-generated holograms (CGHs). The effect of random phase in the interpolation method is confirmed. We extend the interpolation method to kinoforms. Some optical experiments show a good agreement with computer simulations.
On resonance effects in diffractive elements
Author(s):
Thorsten Peter
Show Abstract
Resonance phenomena in diffractive structures may cause unique effects. These are pos- sible to incorporate when synthesizing optical elements with certain filter characteristic.
Efficient array illuminators for large-aperture liquid crystal spatial light modulators
Author(s):
Werner Klaus
Show Abstract
In the past, an array illuminator (AIL) consisting of a so-called Talbot plate was mainly considered for concentrating coherent light onto the active areas of an array of micro-electrooptic components 1. A Talbot plate commonly consists of a one-dimensional multilevel phase grating and transforms at certain distances, called the fractional Talbot distances, a plane wave into an array of light stripes with a duty cycle (DC) of equal or less than 50% 2. The Talbot distance itself is defined as = 2D2 / X where D denotes the grating pitch and X is the optical wavelength.
Enlarging holograms under white light
Author(s):
José J. Lunazzi
Show Abstract
We report the enlargement of holograms by illuminating with a halogen lamp from the small format of 3 5mm. A special configuration is employed to concentrate the luminous energy on the projection lens. An enlargement factor of 20 was obtained in a 75cm x 114cm holographic screen.
Wiener filtering for pattern recognition coarse approximations
Author(s):
Hanni Inbar
Show Abstract
Recently, we have shown [1] that conventional joint transform correlator (JTC) systems can be modified to detect presence of patterns corrupted by colored noise via Wiener filtering (WF). We investigate in this paper pattern recognition ability of systems when WF is only roughly approximated, and present extensive simulation results of such cases.
Phase encoded input scenes for pattern recognition of partially occluded targets
Author(s):
K. Styczynski
Show Abstract
The pattern recognition based on the comparison of Fourier transforms of the target and the scene was adopted to identify occluded objects [ 1]. A method based on the filter frequency selection was used. Here, we will show that by the simple phase encoding of the input scene the recognition results can be still improved.
Human-face recognition by the use of an incoherent optical system
Author(s):
Guofan Jin
Show Abstract
We present a scheme for the optical implementation of human-face recognition with only an incoherent optical correlator. The system uses complementary-encoding hit-miss transform method to improve the performance of the standard correlator. According to this method, we have built up a compact system for human-face optical recognition. We have built a face library in which 96 photographs are stored and the recognition speed of the system is 8 pictures per second.
Improvement of holography by moving gratings and optical bias
Author(s):
Zhao Qi Wang
Show Abstract
Moving gratings is an effective method to improve the diffraction efficiency of dynamic gratings. However there is a sudden drop in the optimum fringe velocity when the fringe modulation is close to unit, which restricts its applications. We experimentally showed that optical bias is an effective method of overcoming this problem. We also found that within a certain range of optical bias, the absolute diffraction efficiency can be higher than that without optical bias, which is not the case when using a stationary grating.
Utilization of cellular automata phase unwrapping method in 3D sensing
Author(s):
Xianyu Su
Show Abstract
Cellular automata are mathematical idealizations of physical systems in which space and time are discrete. A cellular automata is composed of discrete lattice of identical sites. The site evolves according to a set of local rules, the rules specify the value of a particular site in terms of its old value and the values of sites in some finite neighborhood. The utilization of cellular automata phase unwrapping method in 3-D sensing of complex object shapes has been studied. By constructing binary control mask using intensity modulation analysis method, we can unwrap complex phase maps. The experimental results of a human jaw model are given.
New PMP method with two-frequency grating projection
Author(s):
Jie-lin Li
Show Abstract
In phase-shift phase-measuring profilometry [1,2], an equivalent wavelength of the system could be defined as = P where p0 is the mean fringe pattern period at the reference plane, and e is the angle between the P. 0 direction of projection and the direction of observation. Increasing of equivalent wavelength leads to slowing down of the fringe phase variation. It would be benefit to phase unwrapping , but in the same time it leads to lower measurement accuracy. Here we present a new method. Considering both the reliability of phase unwrapping and the measurement accuracy of the system, we make two sets of fringes with different frequencies on a single grating pattern. Instead of using N (N=3,4,5 ...) phase steps, 2N phase steps is used. The phases of the two frequencies are calculated separately. It's possible to unwrap the high frequency phase, with reference to the low frequency phase.
Sampled hard edge reconstruction: definition of frequency modulation function for a sampling-reconstructing system (not quantized)
Author(s):
I. Sanz
Show Abstract
In Fig. 1 , we introduce a systematic diagram of a simple sampling-reconstructing system (SRS) where X„, is the sampling interval and xc. is the filter cutoff frecuency.We asume a non isoplanatic system.Therefore, one avoids applying linear system properties.The meaning of a MTF associated with the SRS is here not fully related with standard MTF definitions. We analyze the system response to an edge , and apply the well known transformation LSF/MTF. As the Sampling Theorem states , functions with non-compact support cannot be entirely reconstructed. Main problems are : a) lossing of high frecuencies. b) Modification in low frecuency carrier due to aliasing. Following the mentioned theorem we analyze the influence of various filter functions in the sampled reconstructed hard finite edge. Analyzing the corresponding responses we shall introduce the concept of frecuency modulation function as an alternative to standard MTF.The sampled finite hard edge and corresponding spectrum are defined:
Absolute shadow Moire contouring by rotating grating
Author(s):
X. Xie
Show Abstract
A new method of moire contouring, absolute shadow moire contouring by rotating a grating, is described in this paper. In the shadow moire system, the period of the grating is varied by rotating the grating, so that the phase of the moire pattern is changed as well. By selecting suitable rotation angles, four images at different positions of the grating are acquired to obtain the absolute distance from the object to the grating. The theoretical analysis is presented for the method and some experiments have been done to verify the theoretical analysis. The results show that the method is fast and very accurate. The measurable range is directly proportional to the period of the grating and inversely proportional to the angles to which the grating is rotated.
Research on synthetic aperture: microscope
Author(s):
ChunKan Tao
Show Abstract
A new principle of synthetic aperture microscope is desribed by means of synthetic aper- ture principle in the paper. The imaging integral equation and its integral kernel arc discussed. The al- gorithm is introduced and the results are given.
Optical/digital system for fingerprint recognition
Author(s):
V. V. Kotlyar
Show Abstract
An optical/digital system dedicated to the recognition of fingerprints using the directions field is discussed. For constructing the directions field, the proposed optical configuration uses a coherent correlator with a spatial filter consisting of sectional diffraction gratings.
The optical morphological scale-space maps using the spectral filters of complex valued kernel
Author(s):
Yi-mo Zhang
Show Abstract
In this paper, We developed a Optical morphological scale-space mapping(OMSSM) system in which there is a spectral filter of the com- plex value kernel, which plays the role of a structure element with com- puter generated hologram (CGH) techniques. With the continuos zoom of input image the scale transform is performed. There exist no problems in JTC, such as unbalance matching correlated energy, requirement of larger aperture of FT lens and the second Fourier transform operation off-system by computerC 1 , 2 J.
Optical fiber interconnection architecture for parallel multiprocessor system
Author(s):
Yi-mo Zhang
Show Abstract
The optical Fiber interconnection system is a hybrid architecture. It is composed of electronic devices and fiber optics, the former is used for program controlling the to- pology reconfiguration, and the letter is used for transmitting the data and instmc- tions. A 32x32 processor system is set up as 3D parallel multiprocessor system, its interconnection network is the hybrid system.
Experimental research on real-time hybrid joint transform correlator
Author(s):
Yu-Wen Qin
Show Abstract
Using two optical wavefront-division multiplexers (OWDMs) in a joint transform correlator (JTC), the real-time high-efficiency JTC, high-speed JTC and four-channel JTC are realized. The JTC have also been used in the domain of morphological complex-valued kernel scale- space image processing. In this paper, the principles and the experimental results of the above experiments are given.
Preparation of a matrix-addressed spatial lighter modulator using ferroelectric liquid crystal
Author(s):
Keshu Xu
Show Abstract
Spatial light modulator are fundamental device in optical information processing and optical computing. We have developed a matrix-addressed frrroelectric liquid crystal spatial light modulator TR:51AD with 6-I *64 pixels. the dimension of each pixel is 80ium*SOpm, its contrast ratio exceed 60:1 and the ,;frame rate exceed 3011z. the driver of FLCSLAI also has been manufactured. It enables the FLCSLAI to realize display in video rate under the control of computer.
Combined binary phase holograms for optical information processing
Author(s):
Ho Hyung Suh
Show Abstract
We have developed a novel method of combining two binary phase holograms in order to suppress the unwanted diffraction order beams effectively. The properties and experimental results of combined binary phase holograms are presented.
A new method of high accuracy dynamic positioning using diode lasers
Author(s):
Jinsong Han
Show Abstract
With liner frequency modulation property of a diode laser and the technique of dual-wavelength fine division, the zero OPD point of an interferometer is dynamically searched with a very high accuracy of 0.015 micrometer. Compared to that of the traditional white light positioning, the interferometer of diode laser positioning is simplified, and the searching range of the zero OPD point has been increased greatly.
Optical/digital neuroprocessor: an approach to neurocomputer
Author(s):
Yanxin Zhang
Show Abstract
A hybrid neuroprocessor(NP) with bipolar optical interconnections and a personal computer(PC) for nonlinear operation and system control is described. The interconnection topology of the 1024 neurons in the processor can be constituted either a single layer feedback network or a multilayered feedforward one. By using different optical interconnection weight masks(IWN4i) and corresponding PC program, a variety of processing tasks can be performed in the NP.
Referenceless hologram based imaging at wave parameter values going to unity
Author(s):
P. V. Polyanskii
Show Abstract
Reduction of imaging (associative) properties of a reference- less hologram as the registration plane moves to far-field re- gion (i.e., as the wave parameter approaches unity) is •conside- red. It is shown, that anomal intensity decreasing at the ghost image in the nearest vicinity of the readout part of an object as well as reduction of signal-to-noise ratio at associative reconstructions are explaned with account of the filtering ac- tion of a free space and intrinsic scale of an object field, rather than from aperture limitation that is the main factor of image degradation figuring into conventional telescopic imaging or ofit-axis holography.
Glitter patterns analysis of rough surfaces
Author(s):
Josué Alvarez-Borrego
Show Abstract
Several random bi-dimensional rough surfaces with known Gaussian statistics were made in the laboratory. The surfaces were coated with a thin film of aluminium to increase the surface reflectivity. Light coming from a source is incident to the surface at an angle theta and the light is reflected from the surface according to the distribution of slopes. Glitter patterns were measured with a CCD to differents reflection angles. Statistical properties were obtained and analyzed. At the same time, glitter patterns of sea surface were analyzed in order to obtain statistical properties of the surface heights. The results show that it is possible to obtain statistical properties of the surface heights from their glitter patterns.
Blind deconvolution by iterative Fourier transform algorithms
Author(s):
T. Takahashi
Show Abstract
We propose a blind deconvolution technique based on iterative Fourier transform algorithms. It has the convergence property although it needs many iterations and a support constraint. The deconvolution is accomplished completely in the noise free case. We also investigate its performance for the contaminated case.
Non-linear process applied to multiple correlations in pattern recognition of defocused images
Author(s):
A. Vargas
Show Abstract
In Pattern Recognition problems, the input scene of an optical system setup could present some optical or physical degradation like as defocusing. In that case the pattern recognition process may be affected, depending of the kind of filter that is used [1]. In general, both the correlation and the crosscorrelation peaks decrease when the amount of defocusing increases, with the result that the discrimination capability (DC) decreases as blurring increases.
Robutness in color pattern recognition against illuminant changes in image acquisition
Author(s):
M. Corbalan
Show Abstract
We evaluate the variations of the RGB components of an image captured by a color 3CCD camera when the illuminant light changes. We consider their ,,possible effects in pattern recognition by multichannel optical correlation. Illuminant sources are limited to three: daylight, fluorescent and incandescent. For such illuminants and adjusting the white balance of the camera the recognition method is robust against lighting variations.
Pure phase correlation implemented by an optoelectronic set-up
Author(s):
E. Ahouzi
Show Abstract
The Pure Phase Correlation (PPC) method improves the sharpness of the correlation peaks, the light efficiency, and the discrimination capability [1,2]. Some optical implementations of the PPC have been proposed [2,3,4,5]. This contribution presents experimental investigation of the hybrid optoelectronic Pure Phase Correlator that we have proposed in [5]. The blocking technique is used to improve the discrimination capability of the system. .
Digital halftoning for computer-generated holograms
Author(s):
Katsuhisa Hirokawa
Show Abstract
A novel computer-generated holograms based on the digital halftoning technique is proposed. The influence of halftoning patterns on a reconstructed image is numerically investigated.
Multi phase only filter design by simulated annealing algorithm in similar pattern recognition
Author(s):
Jin Seon Yun
Show Abstract
Multi phase only filters improve the value of correlation peak and increase twice in space-bandwidth product. Using the simulated annealing algorithm to encode MPOFs, we obtain good correlation characteristics for optical similar pattern recognition. The digitized aircraft images for input pattern are characterized in out-of-class set.
Optical implementation of Baker's map using parallel feedback system
Author(s):
Wataru Watanabe
Show Abstract
As an application of optical parallel computing, optical implementation of the baker's map is studied. Using optically addressed spatial light modulators, an optical feedback system has been constructed. We have confirmed that a fractal set can be generated optically by iterative baker's map on the experimental system.
Photofabrication in optical system fabrication
Author(s):
Keiichiro Kagawa
Show Abstract
We study potential capability of a photofabrication technique for fabricating optical elements as well as their packaging. For the purpose, we executed a series of fundamental experiments. According to the results, we propose a novel technique to make lenses with two successive processes.
Pattern detection with polarized spatial filter
Author(s):
K. Shimizu
Show Abstract
In many researches concerning with optical pattern recognition by spatial filtering techniques, light amplitude, intensity or phase information have been utilized. In this paper, we propose to use the state of polarization for pattern recognition and discuss its availability as a new method of pattern detection. For the particular contrast objects, the higher detection of polarized spatial filtering than the amplitude filtering methods have been obtained.
Joint radon-elfin transform correlator for scale, rotation and shift invariant pattern recognition
Author(s):
Yaming Wu
Show Abstract
Radon transform can transform orthogonal coordinate space to Radon space with simple rotation and shift coordinate transform relationship. Radon transform followed by MeIlin transform, i.e., Radon-Mellin transform, is shown to provide scale, rotation and shift invariant correlation in Joint transform correlator by a series of one-dimensional (1-D) MeBin transformed projection correlations to utilize many excellent devices for 1-D signal processing with the advantage of change of reference pattern in real-time and without utilizing complicated synthesized filters.
Functional approach to the inverse problem of photon counting statistics
Author(s):
Vitalij N. Kurashov
Show Abstract
A common problem in the measurement of photon-count statistics is to estimate the probability density function (PDF) of light intensity from those of photon counts. Considerable recent attention has been focused on this problem in the context of astronomical speckle interferometry, where the statistics of the speckle pattern are used for image reconstructionl. As this problem is typically ill-posed, its direct solution is unstable and requires some regularization procedures. Among them, the algebraic solution with Tichonov's regularization2, asymptotic estimators3, and Pade approximants4 were proposed. We formulate here a different approach to the problem which gives quite acceptable results with reasonable facility.
Analysis of convergence property of the Fourier iterative blind deconvolution algorithms
Author(s):
Masayuki Hattori
Show Abstract
Effectiveness of the Fourier Iterative Algorithm (FIA) for Blind Deconvolution has been shown by computer simulations. In this paper , we analyze its convergence property theoretically. FIA for recovering burred images convolved with unknown PSF and objects, is configured as Fig.1 considering two major facts.
Optical complex-valued matrix-vector architecture using stacked negabinary-encoded outer-product multipliers
Author(s):
Guoqiang Li
Show Abstract
Based on negabinary encoding and weighting-shifting operation, a stacked optoelectronic outer-product complex multiplier module is proposed. By matrix partitioning and cyclic flow of the vector element, complex matrix-vector multiplication of arbitrary size can be performed using a limited number of such modules. The proposed methods are more efficient and have advantages in space-time bandwidth product.
Defect enhancement in periodic patterns with a bacteriorhodopsin film
Author(s):
Takayuki Okamoto
Show Abstract
We present a real-time optical system for defect enhancement in periodic patterns using spatial filtering with photo induced anisotropy in bacteriorhodopsin films. We use a property that the anisotropy depends not only on the intensity of an exciting beam but also on that of probe beam. This system is also applicable to moving objects.
Defect enhancement of periodic structure using dye-doped liquid-crystal cells
Author(s):
Jun-ichi Kato
Show Abstract
A nonlinear spatial filtering based on light-induced birefringence change in dye-doped liquid crystals has been applied to defect inspection of periodic structure. Photoisomer- ization of azo-dye molecules leads to local reorientation of the liquid-crystal molecules, by which polarization of the transmitted light is modulated depending on the incident light intensity. By selecting suitable polarization of the transmitted light, a self-aligned spatial filtering is realized. The filtering performances have been experimentally investigated.
Investigation on self-pumped phase conjugate properties of barium titanate
Author(s):
Yulin Li
Show Abstract
A study on self-pumped phase conjugate properties in BaTiO3 crystal is presented. The relation between phase conjugate reflectivity and the input position as well as incident angle is investigated quantitatively, with experimental results given. The conclusion is helpful to improve the research work on interconnection and associative memory using BaTiO3..
Storage and associative recall of images by stimulated photon echoes
Author(s):
Yong R. Kim
Show Abstract
The photon echo is unique among nonlinear optical effects in that it involves interference and diffraction in both space and time domain. This intrinsic spatio-temporal property offers multitude of interesting and useful applications in optical storage and processing of temporally as well as spatially encoded data. In this paper we consider the possibility of using stimulated photon echo (SPE) to implement all-optical associative memory of spatial data.
Analysis of the output intensity distribution of the tracking novelty filter
Author(s):
Junghee An
Show Abstract
With a tracking novelty filter, using the destructive interference of two-beam energy coupling, moving features of phase object can be detected as its output image. From the intensity distribution of the output image, information about movement of phase objects is calculated, then the temporal and spatial resolution of the tracking novelty filter is examined.
Optical image switching system based on the BPEJTC
Author(s):
Sang-yi Yi
Show Abstract
In this paper, a new real-time optical image switching system based on the binary phase extraction joint transform correlator (BPEJTC) is suggested. The phase filter which has the arbitrary position mapping function between input and output plane is constructed by using the modified joint transform power spectrum (JTPS) of the BPEJTC. Then, the input image is multiplied by this phase filter in the spatial frequency plane and through further Fourier transform the input image is switched to the new positions in the output plane where the correlation peaks are occurred. The practical optical switching system is opto-digitally constructed and through some experiments the possibility of real-time implementation of the image switching system is suggested.
Holographic recording in polyesters having cyanoazobenzen units in the side chain
Author(s):
Kazuo Nakagawa
Show Abstract
Recently, there has been much interest in polymer films having azo dyes in the side chain because of their ability to record optical information1,2) . The irradiation of linearly polarized laser beam on azo-dye-doped polymer films induces optical anisotropy due to trans-cis photoisomerization of azo dyes3) . If the photoinduced anisotropy can be preserved for a long time, the polymer films work as optical recording materials.
Computer-generated Fresnel hologram for three dimensional object
Author(s):
Kunihiko Mori
Show Abstract
Computer-generated Fresnel hologram (Fresnel CGH) for three dimensional object can be made by two-dimensional Fourier transforms of each images sampled at a direction of depth1). However, the computing time is proportional to the sampling number on depth. Therefore, only the object with finite information on depth can be recorded by this method. The Fresnel CGH for three dimensional object composed of several planar segments was also reported2).
Rotation invariant pattern recognition with multiple circular harmonic expanssions
Author(s):
Wanji Yu
Show Abstract
A multiple circular harmonic (CH) expansion filter has been developed to rotation invariant pattern recognition with the joint transform correlator. By correctly choosing the number and orders of circular harmonic expansions of the object, the mostly similary patterns, which have the propability to get false detection when just single CH expansion is considered, can be discriminated.
Development of computer informational system of diagnostics integrated optics materials, elements and devices
Author(s):
A. E. Volosovich
Show Abstract
Diagnostics of materials, elements and devices (DMED) of integrated optics (IO) are comparable in cost with their production. It is very important for the development of IO devices . Each level requires a certain amount of equipment. In this work we consider some questions of diagnostics in a distributed CAD system 1 at various levels of computer support while using a paper-free technology.
Photoinduced superfast nonlinear processes in bacteriorhodopsin films and their application for real time optical information treatment
Author(s):
E. Y. Korchemskaya
Show Abstract
Real time holographic information treatment is needed in optical reversible nonlinear materials with cycle recording-erasure time of less than 40 ms. There were several applications of polymer films with protein bacteriorhodopsin (BR) for real time holographic information treatment [1 - 3]. This optical nonlinear material has very high photosensitivity (several milliwatt CW visible laser irradiation), extremely good reversibility [4]. Only properties of photochromic local response of BR polymer films were applied in all these works, but this optical medium is unique in combination of optical properties. In this work, superfast holographic recording mechanism is revealed in BR polymer films. Also it is proposed the application of this mechanism for efficient vibration registration and holographic correlator.
Light polarization modulation and selective image processing using photoinduced anisotropy of bacteriorhodopsin films
Author(s):
E. Y. Korchemskaya
Show Abstract
Reversible photoinduced anisotropy of polymer films with protein bacteriorhodopsin (BR) have attracted a lot of attention for real time optical processing [1, 2]. The high photosensitivity of these films allows the processing of low-power optical signals (several milliwatt CW visible laser irradiation). Spatial resolution does not fall below 5000 lines/mm, require no external processing, and images can be recorded and erased over <106 cycles without degradation. Compared with the photorefractive crystal, BR polymer films offers the advantages of lower intensity requirement and much larger space-bandwidth-product. This work shows possibility of the application of BR polymer films for the light polarization modulator with purely optical control and for real time selective image processing resulting from photoinduced anisotropy of BR polymer films.
Phase-only-multiplexed holograms
Author(s):
E. Carcolé
Show Abstract
We perform a basic mathematical analysis of the phase-only-hologram by taking the phase corresponding to a linear combination of N weighted phase functions. We show that this phase only hologram may be written as a new linear combination of the original phase functions with new weights. Also some non desired new terms appear and are written in terms of the original phase functions. The particular case of a trifocal lens is analyzed.
Sinmyung laser system in KAIST and development of lasers using SBS cell
Author(s):
Hong Jin Kong
Show Abstract
A high-power Nd:glass laser system (Sinmyung I) has been constructed and tested in KAIST[1]. In this system, we used a Nd:YLF laser as a master oscillator, a 4-pass amplifier for pre-amplification[2], Nd-doped phosphate glasses for rod amplifiers, and spatial filtering and image relaying units. The system has demonstrated in excess of 80 J at 40 ps full width at half-maximum (FWHM) pulse duration. Output gains, energies and spatial profiles were measured at each amplification stage. X-ray generation experiments in Cu bulk target was done using this system.
Development of a compact, far-infrared, free-electron laser
Author(s):
Jongmin Lee
Show Abstract
A compact tunable free-electron laser (J L) is being is being developed at KAM. The wavelength of the laser is tunable in the wavelength range f min 25 μm to 50 μm. The FEL generates a train of short-pulse (10 ps) micropulses with a repetition rate of 2.8 GHz. The peak power of a micropulse is expected to be 100 kW. The FEL system is composed of a microtron accelerator, a CW electromagnet undulator, and an optical resonator. The FEL system will serve as a user facility for the study of photochemistry, molecular rotation, surface physics, solid-state physics, biophysics, etc.
Combustion characteristics of a planar flame burner as a calibration source of laser diagnostics
Author(s):
Yong Suhk Gil
Show Abstract
We studied the combustion characteristics of a planar flame burner to provide a standard source for temperature and chemical species in combustion for calibrating an optical system and developing a new laser diagnostic method. CARS measurement of temperature and LIF measurement of OH radical concentration on the burner were performed and compared with numerical analysis.
Laser-induced photoacoustic spectroscopy (LPAS) with a highly sensitive sensor for trace speciation of aquatic actinides
Author(s):
W. Hauser
Show Abstract
The laser-induced photoacoustic spectroscopy (LPAS) has been developed [1 - 4] and successfully applied for the chemical speciation of aquatic actinide ions in trace concentrations [4 - 6]. Additionally, LPAS has been used for analytical applications, e.g. for trace detection of inorganic contaminants [7]. The method is found to be compatible with the conventional UVNIS spectroscopy in the spectral range of available dye lasers but having a distinctive advantage for the speciation sensitivity. However, the main difficulty for a routine laboratory use of LPAS has been a detection unit for acoustic signals generated within a given sample solution.
LD-pumped femtosecond Nd-doped fiber laser started with a moving mirror
Author(s):
J. M. Lee
Show Abstract
The start-up of passive modelocking with a moving mirror was demonstrated in a Nd-doped fiber laser pumped by a single-stripe laser diode. The absorbed pumping power was as low as 50 mW for the start-up of modelocking. Pulses with duration of 250 fs and energy of 140 pJ were generated.
Self-starting mode locking in a dual core ring fiber laser
Author(s):
E. Martí-Panameño
Show Abstract
Numerically we demonstrate the self-starting mode locking, in a dual core ring fiber laser. Our mathematical model takes into account Kerr nonlinearity, the group velocity dispersion, the full gain line for the active ions, the pump depletion, and the feedback of the passive core.
Transverse mode-locking of Ti:sapphire lasers
Author(s):
K. W. Sun
Show Abstract
In this paper, we report the observation of the self-starting in a self-mode-locked Ti: sapphire laser when the laser is operated in high order transverse modes. Self-starting of this laser was demonstrated at various wavelengths and cavity lengths without any additional elements been applied. Stable pulses shorter than 100 fsec in duration were obtained at a wavelength near 778 nm.
Twist effects on the polarization properties of high birefringent fiber lasers
Author(s):
Ho Young Kim
Show Abstract
In this presentation, the effects of twist in fiber laser cavities on the polarization properties of the high linear birefringent fiber laser are reported. The directions and frequencies of two polarization eigenmodes are found to be a complicated function of the twist rate. At low twist rate, the directions coincided with the fiber main axis and their beat frequency did not decrease monotonically. Experimental observations in high birefringent fiber laser will be explained by a simple theoretical model.
Measurements of temperature quenching effects in nd-doped alumino-silicate optical fiber preforms
Author(s):
L. A. Zenteno
Show Abstract
It is well known that Al doping increases the miscibility of Nd doped silicate glasses, leading to reduced concentration quenching [1]. This is particularly important in applications involving output power scale-up in Nd-doped double-clad fiber lasers since it permits higher pump absorption efficiency, shorter fiber lengths and increased quantum efficiency [2]. However, as pump power in the tens or even hundreds of watts range becomes available from GaAs laser diode bars [3], the degradation of Nd-fiber laser quantum efficiency with increasing temperature (temperature quenching) may become significant. [4]
Mode-locking and prelase single-axial-mode q-switching of Bd:YvO4 lasers pumped by laser diode
Author(s):
Chuandong Li
Show Abstract
Mode-locking of LD pumped Nd:YVO4 laser is reported for the first time. The pulse width is about 43ps with the output power of 7mW. This width is much more narrower than the theoretical prediction. Strong amplitude modulation in relaxation oscillation is observed at the very low pump brightness. By prelase Q-switching, single-axial-mode lasers with peak power of 50W is achieved. These results can be improved to higher level by optimum designing of systems.
Laser characteristics of tellurite neodymium-doped glass
Author(s):
Bing Xu
Show Abstract
The laser characteristics of a gain-switched tellurite neodymium- doped glass laser excited by a Ti: sapphire laser are reported for the first time to our knowledge. An efficiency of 14.7% was obtained in a nonoptimized laser. The temporal outputs of the glass laser were observed.
The wavefront analysis of NbUr Nd:YaG laser output beam using a Mach-Zehnder interferometer
Author(s):
Sueng-Ho Choi
Show Abstract
We have constructed and tested an imaging unstable ring resonator of Newtonian telescope type with an infinite Fresnel number for Nd:YAG laser oscillator. The wavefronts characteristics is analyzed based on the fringe patterns from Mach-Zehnder interferometer. We observe the approximately uniform intensity profile and wavefront phase over the transverse plane. Fringe analysis by using Fourier transform method shows that the distortion of wavefronts is less than 0.2 λ. In comparison with the wavefront flatness of a standing-wave-type laser output beam, that of the NBUR Nd:YAG laser output beam was enhanced by up to 75 %.
Generalized self-filtering unstable resonator in an ablative flashlamp dye laser
Author(s):
A. Hariri
Show Abstract
The result of an experimental study in an ablative flashlamp dye laser using a generalized self-filtering unstable resonator (GSFUR) with a low magnification of M = -1.62 is presented. The output laser beam in both near- and far-field has nearly Gaussian distributions with a pulse duration of ~ 450 ns at the lasing threshold. The laser is characterized by a nearly diffraction-limited beam divergence of 1.1 mrad with superior beam radiance and tolerance to mirror misalignment in comparison with the plane-parallel resonator of equal cavity length.
Comparison of upconversion efficiencies between STEP and SHG mediated upconversion process in an Er3+ doped LiNbO3 crystal
Author(s):
J. J. Ju
Show Abstract
The science for near infrared (NIR) pumped blue/green lasers has been an intense research field for display and data storage applications. Second harmonic generation (SHG) in nonlinear optical (NLO) crystals1 and upconversion lasing in rare earth doped solids2 have been promising approaches. The infrared to visible upconversion efficiencies for any case are of paramount importance for practical applications. Auzel3 compared the efficiencies for cw NIR laser excitations in different media, demonstrating that the fluorescence due to sequential two-photon excitation process (STEP) in a doped crystal is orders of magnitude stronger than SHG in a pure NLO crystal because real (resonant) transitions are involved in the STEP, in contrast to the SHG. However, with pulse laser excitations, the opposite can be true because SHG efficiency depends on the peak intensity of the pump pulse.
Studies of a new sub-mm p-Ge laser
Author(s):
Kijun Park
Show Abstract
A p-Ge FIR/submm laser placed in Voigt-configured permanent magnets with Cu heat sinks gives a 3-fold increase in repetition rate to 120 Hz and a 100-fold increase in energy output compared with usual Faraday-configured lasers.
Dual amplified spontaneous emission in some amino-coumarins
Author(s):
P. K. Palanisamy
Show Abstract
The dual frequency Amplified Spontaneous Emission (ASE) bands observed in certain aminocoumarin dyes under nitrogen laser excitation were explained as due to the planar and the twisted intra molecular charge transfer (TILT) con- formations of the dye in the excited state. This paper presents a study of small signal laser gain of aminocoumarins with different substitutions in a variety of organic sol- vents.
Analysis of a water jet by laser induced breakdown spectroscopy
Author(s):
Ota Samek
Show Abstract
This paper is concerned with the application of the technique of Laser Induced Breakdown Spectroscopy (LIBS) for the analysis of liquids. Electron densities and plasma temperatures for the laser-produced plume were derived, using the Saha- Boltzmann equation, from line profiles of the Stark broadened H(beta) and H(gamma) lines. Calibration curves for various trace elements in water were derived using the principle of internal standardization for quantification.
Measurement of cavity loss and threshold gain in a vertical-cavity surface-emitting laser using an external mirror
Author(s):
K. H. Ha
Show Abstract
The threshold gain and the cavity loss are important parameters for the optimum design of vertical-cavity surface-emitting lasers(VCSELs). The internal loss is commonly determined from the dependence of the external slope efficiency on cavity length[1]. This method inevitably assumes that internal loss is same for each devices. Here we try to determine the cavity loss by varying the amount of light fed back to the VCSEL using an external mirror. The schematic diagram of the experimental setup is shown in Fig. 1. The tested VCSEL consists of super lattice structure surrounded by AlAs/Al0.3Ga0.7As distributed Bragg reflectors. Current is constricted by proton implantation outside a 15- μm diameter circle. A 15- μp m opening in the p-metalization acts as an output aperture. In the continuous wave operation, the threshold current of VCSEL undergoes a periodic change depending on the external cavity length. We found the position of the minimum threshold current by using a piezo-electric translator to the external mirror. Then, we measured the threshold current for different values of feedback.
Global stability, self pulsation and frequency locking of a two-level model for a class-b laser with feedback
Author(s):
Peng-Ye Wang
Show Abstract
The global stability, self-pulsing oscillation and frequency-locking properties of a two-level model of a class-B laser system with external feedback is analyzed. In the parameter plane of the feedback the phase diagram, or the boundary between the stable and the unstable region, is obtained by linear stability analysis. With numerical simulations, the period and amplitude of the self-pulsing oscillation in the unstable region versus the control parameters are obtained. Chaos is also found inside the unstable region. Frequency-locking Arnol'd tongues are obtained when an external modulation is applied to the system.
Timing jitter reduction of a gain-switched semiconductor laser by external injection-seeding
Author(s):
Dong-sun Seo
Show Abstract
Ultra-short optical pulse generation from gain-switched semiconductor lasers is important for applications such as time-division multiplexed optical communication systems, optical sampling, and soliton generation. Considerable research interest has been focused on reducing pulse widths to sub-picosecond levels. However, as the pulse width is made shorter, pulse-to-pulse timing jitter becomes important and can limit system performance, through such parameters as bit error rate and temporal resolution. Recent work shows that self or, external injection-seeding reduces timing jitter in gain-switched Fabry-Perot (FP) lasers.1,2 We report an experimental investigation of the impact of external seeding on timing jitter in gain-switched FP and distributed feedback (DFB) lasers and show that the timing jitter can be greatly reduced by external injection-seeding with continuous (CW) light, regardless of the laser structure, i.e., FP or DFB. We also show that there exists an optimum seeding power to obtain short pulses with low timing jitter.
Radiation synchronization in the four-channel, efficient waveguide CO2 lasers
Author(s):
M. Kopica
Show Abstract
The paper presents the new experimental data of advanced version of four channel, matrix, waveguide CO2 laser. The unitary power on the level of 2 W/cm of length has been obtained. The phase characteristics show the full synchronization of four beams and gaussian distribution of laser beam in the far field.
Simple generation of picosecond dye laser pulses adjustable spectrally between near UV and IR using a standard nanosecond pumping laser
Author(s):
Nguyen Dai Hung
Show Abstract
Results in study of the spectro-temporal selection method to produce picosecond dye laser pulses adjustable spectrally between 321 nm and 783 nm are presented. Adjustability of the picosecond pulse wavelength, possibilities of extension of this method to different dyes, different pump wavelengths, possibility of the generation of shortest STS pulses and transform-limited picosecond pulses, stability of the output pulse duration and intensity are reported. From these results, production of picosecond (50- 100 ps) dye laser pulses of spectrally adjustability is obtained in a compact and simple device with a standard nanosecond pumping laser.
Excitonic transitions in GaN epitayer layers grown by MOCVD
Author(s):
Guangde Chen
Show Abstract
Optical transitions including free-and impurity-bound excitors in both n and p-type GaN epitaxial layers grown by MOCVD have been studied by time- resolved photoluminescence measurements. The radiative recombination lifetimes of the free excitions and excitons bound to neutral donors and acceptors in GaN have been obtained.
Khz-level excimer laser of cylindrical cage type for lidar
Author(s):
Hong Jin Park
Show Abstract
Discharged-pumped excimer lasers[1] with a compact type[2], high repetition rate[3], long life time operation[4] are required for the laser sources for lidar application[5]. The physical conditions include, above all, the retention of homogenity of the discharge volume at a high pulse repetition frequency for this laser. This is usually done by replacing the gas in the electrode gap which refines circulation by various fan systems. The stable discharge and the high velocity of a few ten m/s are necessary for the kHz order repetition-rate laser[6]. For this purpose, we have developed a compact KrF excimer laser of cylindrical cage structure and investigated the characteristics of laser output, repetitive operation and long life from this system.
Raman and optical spectra of Mn5+-doped Ba3 (Vo4) 2 and Ba3 (v1xTaxo4)
Author(s):
Jun Xu
Show Abstract
Different Raman spectra and lattice parameters of Mn5+-doped Ba3 (VO4) 2 and Ba3 (V1-xTax04) 2 (0 < x< 0.5) were described. The optical spectroscopy and lifetime of Mn5+ in Ba3 (V04) 2 and Ba3 (V1-xTax04) 2 were also presented and analyzed. It' s suggested that Mn5+ enters a relatively weaker field in Ba3 (V1-xTax04) 2.
Gaussian optics of asymmetrical interferometers with zero optical path difference
Author(s):
V. Prokhorenko
Show Abstract
The Sagnac Interferometer (SI) selectivity nature has been investigated. Different active media in laser cavities can be present as composition of optical wedge, lens or transparency. The case of SI selectivity for optical element placement inside interferometer, when this element can be present as a lens F (Figure 1.) has been discussed. The mathematical model of SI in matrix presentation is represent too. This model can be use for real laser cavity's calculations.
Increased efficiency of an atmospheric-pressure XEF(c->a) laser with an electron-beam excitation
Author(s):
Han-Yong Ryu
Show Abstract
The most interesting features in the fields of laser engineering and laser physics are efficient generation of new wavelengths, compact size of devices, analysis of unknown kinetics, feasibility of various applications, high power, and high efficiency etc. In view of these terms XeF* excimer has many attractive points. Recently, the blue-green XeF(C->A) laser has been investigated in various operational modes to obtain high-energy and high-efficiency under the high excitation rate with high pressure[1] and low excitation rate with intermediate pressure of laser gas[2]. Furthermore operational characteristics of atmospheric-pressure are newly focused[3-5]. The use of laser medium with low pressure (≤1 atm) is proposed for solving nonlinear problems in ultrashort pulse amplifier[5]. Also that condition offers several advantages such as the use of thin optical windows, easy handling, and low cost. This paper describes the increased intrinsic efficiency as a functions of Xe concentration for the condition of atmospheric-pressure XeF(C->A) excimer laser with electron-beam (e-beam) excitation.
Depolarization degree of diode-pumped single frequency monolithic ring Nd:YaG laser
Author(s):
G. D. Laptev
Show Abstract
We present experimental results of investigations of the depolarization degree of the diode- pumped monolithic ring Nd:YAG lasers (ring chip-lasers). The obtained value of depolarization degree of single frequency ring chip-lasers is about 10-3. We discuss mechanisms of the radiation depolarization of the monolithic Nd:YAG lasers.
Development of Nd:YaG(2w)-Ti:sapphire laser system for pollution lidar
Author(s):
Yong Woo Yi
Show Abstract
The pulsed Ti:sapphire laser of narrow spectral linewidth, high pulse energy, and wide tenability is attractive for various applications such as spectroscopy, DIAL measurements of atmospheric species[1] and difference frequency mixing (DFM)[2]. As the energy loss of laser oscillator is increased to obtain the narrow spectral linewidth, an amplifier is required to obtain high power, And maximizing the extraction efficiency of amplifier is very important for compact laser system.
Thermal lensing and aberrations in diode-end-pumped solid state lasers
Author(s):
J. K. Jabczynski
Show Abstract
Thermally induced gradients of refractive index play a fundamental role in laser mode formation in diode-end- pumped lasers. The divergence and beam quality as well as efficiency and stability of generation depend on a heat distribution in active medium. The paper is devoted to theoretical and experimental investigations of influence of temperature gradients on optical parameters of output beams. The investigations were made for several active media (Nd:YAG, Nd:YLF, Nd:YVO4 , Nd: S-VAP, Nd:LSB ). Laser and thermooptical parameters of these crystals are presented in Table 1.
The comparitive study on c derivatives by femtosecond time-resolved optical Kerr effect and z-scan technique
Author(s):
Y. H. Zou
Show Abstract
Femtosecond time-resolved optical Kerr effect and Z-scan technique were used to measure the third-order nonlinearity of the adduct of C60 with Cyanamide(C60-NHCN) and its Cr(NO3)3 complex(C60-NHCN-Cr).The ultrafast measurement determined the nonresonant y1111 values of 3.4x10-31 esu and 2.2x10-31 esu respectively. However the Z-scan technique by a He-Ne laser gave extremely large V1111 values due to the accumulated long time effects.
Laser photoacoustic spectroscopy: a powerful tool for trace gas measurements
Author(s):
D. C. Dumitras
Show Abstract
Laser photoacoustic spectroscopy (LPAS) is one of the most sensitive calorimetric techniques that consists in energy conversion from modulated excitation radiation (laser) to sound energy and it is due to nonradiative transitions that convert a part of absorbed energy into thermal energy. The temperature variations then determine the formation of acoustic waves. At the wavelengths of the CO2 laser (9-11 μm), more than two hundred of molecular gases can be detected with a system based on photoacoustic (PA) spectroscopy, at concentrations as low as ppb or even ppt.
Fluorescence characteristics of near ultraviolet laser dyes and its laser output pumped by hcp
Author(s):
C.H. Oh
Show Abstract
Fluorescence characteristics of near ultraviolet dyes, BBQ and BPBD365 have been investigated for the development of UV dye laser. The dyes were solved in cyclohexan. The fluorescence spectrum intensities against both the excitation wavelength and emission wavelength were measured by a spectrofluorophotometer which could be variable on measuring wavelength from 200nm to 950nm and on both excitation and emission slit width by 3nm to 40nm.
Laser oscillation from argon ionic excimer
Author(s):
Xuelong Liu
Show Abstract
Laser oscillation around 200nm from argon ionic excimer (At2+Ar)2+ 23Pg(bound)-- 13Pu(repulsive) transition is reported for the first time. A 0.5 MeV 20KA 3Ons REB was employed to transversely pump the active media of pure argon. Kinetic process are analyzed numerically: The argon ionic excimer (Ar2+Ar)2+ is a potential laser media which should have wider tuning range than other type of ionic excimers. This broad band tuning character will be significant for practical uses. Using semiempirical Rittner, ab inito and scaling methode, A comprehensive compile of theoretical results for argon are given in fig.1
Laser-induced gratings in carbon dioxide excited via raman-active resonances
Author(s):
R. Bombach
Show Abstract
Results are presented of the first observation of laser-induced gratings excited via Raman-active transitions of CO2 molecules in the gas phase. The experiment is described and the time behaviour of the gratings reflectivity is discussed. Furthermore, the use of measurements of grating excitation spectral efficiency as a Raman spectroscopy method is demonstrated.
Degenerate four wave mixing spectroscopy of atomic and molecular oxygen
Author(s):
E. Konz
Show Abstract
Degenerate Four Wave Mixing (DFWM) spectroscopy of 0 atom 2p3PJ - 3p3PJ two-photon transition and of B3Σ-u - X3Σ-g Shuman-Runge band of the molecular oxygen in the vicinity of 226 nm has been performed. Fine structure of both transitions has been resolved and in case of molecular oxygen most of the observed lines were assigned and transition linewidths have been measured.
Spectral dynamics of all solid-state frequency-shifted feedback laser
Author(s):
Kumio Kasahara
Show Abstract
Frequency shifted feedback (FSF) lasers are lasers which contain an acousto-optic modulator (AOM) as a frequency shifter inside its cavity 1)-2). We are investigating the oscillation mechanism by using a diode-pumped Nd:YVO4 as a gain medium. Remarkable information was obtained on the oscillation characteristics, especially on the unique oscillation spectrum 3). In this paper, it was made clear for the first time that the oscillation bandwidth is defined as the product of lineshape broadening and total mode number of resonant modes. This was determined by using the proposed model based on multiple-beam interference with phase shift according to round-trip in the cavity.
Frequency stabilization of blue (473nm) laser
Author(s):
T. Hara
Show Abstract
LD-pumped solid laser has been widely developed, and it makes possible to obtain visible laser beam using nonlinear photorefractive crystal. This paper report the method and experimental results of frequency stabilization of blue (473nm) laser which is generated from the SHG of Nd+3YAG (946nm) laser using both LBO crystal and H2O intracavity absorption cell.
Dye fluorescence at supersaturated pump fluxes
Author(s):
A. Yu. Belonogov
Show Abstract
A hypothesis of a multifold reduction of exited particle lifetime at supersaturated pump fluxes, suggested in /1-7/ for accounting for an unusual growth of dye fluorescence intensity at high pump fluxes, is analyzed. Registration of profiles of pump and fluorescence pulses of phenolemine F-510 in ethanol solution with lifetime of exited particles τ= 6.6 ns was made with pump fluxes IO = (1023 - 1027) cm-2s-1 at a wavelength of 532 nm. The experimental results testify for preservation of the exited particle lifetime τ= 6.6 ns at high pump fluxes.
Up-conversion in Pr3+-doped gmo crystal
Author(s):
Sun Il Kim
Show Abstract
The up-converted fluorescence of Pr3+ in the Pr3+:GMO crystal is observed at 490 nm and 499 nm(3P0->3H4) when 1D2 level is excited by 595 nm dye laser beam. Both up-converted and ordinary fluorescence show the same lifetime of 200 ns. It is suggested that the sequential two-photon excitation process (STEP) is dominant in the up-conversion mechanism.
Plasma impedance and electron density in a pulsed superradiant gas laser channel
Author(s):
K. H. Tsui
Show Abstract
In gas lasers, the active medium in the laser channel is a weakly ionized plasma. The plasma properties of this active medium are expected to play important roles in the laser performances. Recently, studies in matching plasma impedances of the spark gap and laser discharge channels are reported for pulsed superradiant nitrogen lasers [1-3]. It is noted that the laser pulsewidth under goes a resonant narrowing when the impedances are matched in the charging circuit where the plasmas are modelled by an inductance- capacitance (L-C) parallel circuit phenomenologically [1].
Optically locked diode laser using a high-contrast saturated absorption spectrometer with a grating
Author(s):
J. B. Kim
Show Abstract
By using optical signals obtained by a high-contrast saturated absorption spectrometer as a reference frequency selector, a diode laser frequency has been locked to the hyperfine transition line of Cs atom. We did not use a mirror but a grating in order to exclude feedback of unwanted side modes, which cause mode hopping or oscillating an unwanted frequency whose intensity is not decreased even though passing through the atomic cell two times. Long term stabilization has been accomplished by compensating the cavity length for phase fluctuations.
Asymmetric quantum-well heterostructure laser systems
Author(s):
V. K. Kononenko
Show Abstract
Use of asymmetric quantum-well heterostructures is a new conception of band engineering for semiconductor optoelectronics. In this manner there are developed semiconductor photomultipliers, infrared detectors, optical modulators and amplifiers, generators of harmonics, and other modem nanodevices.
Analysis of coupling losses in waveguide laser with Gaussian mirror
Author(s):
Piotr Witonski
Show Abstract
In 1964, Marcatili and Schmeltzer proposed the use of hollow dielectric waveguides as low-loss components for laser amplifiers [1]. Early workers on waveguide lasers sought definite gain/bandwidth advantages. Nowadays waveguide structures are one of the most commonly used gas laser structures in many applications. Especially among different waveguide gas laser, CO2 laser are extensively investigated theoretically as well experimentally (see Ref.2 and its references). That kind of lasers can run at much highei pressures than conventional Gaussian-resonator lasers, and thus offered increased frequency tenability. One of the most important problems which appear in analysis of waveguide lasers is quantity of generated output beam. However using Gaussian reflectivity mirror as transmission one make possible improve quantity of the beam.
Modelling of Gaussian mirror lasers
Author(s):
Piotr Witonski
Show Abstract
The generation of diffraction limited light beams with high power is of the upmost importance for a number of applications in the field of material working and processing. In order to solve this problem unstable laser resonators that use variable reflectance output couplers have been proposed1-6 and successfully implemented in many gas and solid state lasers7-10 for obtaining large cross-section, diffraction-limited beams.
Study of photophysics processes in organized molecular systems by laser fluorescence spectroscopy
Author(s):
A. Z. Baran
Show Abstract
The photophysics processes in model biological systems types micelles-polymer structures and semiconductor-insulator-adsorbed molecules systems was investigated by laser fluorescence spectroscopy. The fluorescence probe applied to study complex formation and determination of the local dynamic of this systems. The polarization of luminescence of adsorbed monolayer of dyes was studied. The orientation of some type of adsorbed dye molecules on surface semiconductor-insulator structures was determinated. It has been found the influence of the local charged centers of the surface on the orientation of molecules in adsorbed monolayer.
Laser time-resolved spectroscopy of spectral and spatial heterogeneity of fluorescent probe molecules in model membranes
Author(s):
Yu. V. Zvinevich
Show Abstract
The spectral and polarization time-resolved characteristics of the fluorescent probe 1-phenylnaphthylamine (1-AN) [1] in model and red blood cell (RBC) membranes using laser spectrofluorimeter have been studied. It is shown that the electronic spectra of probe in model membranes inhomogeneously broadened. Inhomogeneous broadening affect significantly the spectroscopic properties of probe in membranes, such as the time-dependent fluorescence Stokes shift, the dependence of the fluorescence instantaneous spectra and fluorescence kinetics on excitation wavelength.
The peculiarities of amines fluorescent specters under laser stimulation
Author(s):
V. F. Myslitsky
Show Abstract
The adrenaline and norepinephrine fluorescence specters under laser ultra-violet focused beam were investigated in this work. All measurings were carried out depending on rays explosure intensity the extra fluorescence maximum is formed on the 387 nm wave lenght.
The plasma diagnostics of high-pressure lasers with pumping by transversal discharge
Author(s):
V. S. Shevera
Show Abstract
This paper describes the elaborate of small active elements on eximer molecules, nitrogen and inert gas atoms using transversal discharge, the creation of laser monitoring facility and the investigation results of the plasma absorption and radiation time-dependencies. Also it was described the results of metastable atoms concentration measurements in the mixtures He(Ne)-Xe(Kr)-HCI, He-N He-N -SF and He-Kr(Xe).
Propagation of flattened Gaussian beams
Author(s):
V. Bagini
Show Abstract
In many applications of light beams, a field is required whose amplitude on a fixed plane is as uniform as possible within a certain area and practically vanishing outside. Typical examples are furnished by optical processing, beam shaping and laser cavities. Many different field profiles exhibit such a property, and the most employed one is the so-called Super-Gaussian profile [1], whose use in laser cavities and other applications has given good results [2-4]. Unfortunately, the study of the propagation features of the beams generated by this type of profile is to be handled numerically, and no closed expressions for their paraxial propagation behaviour are available. Recently [5], a new class of top hat profiles has been introduced, the so-called Flattened Gaussian ones. Their main virtue concerns the possibility of expanding these profiles as a. finite sum of Laguerre-Gauss function, so many properties can be exactly obtained. In particular, in this work we describe paraxial and far-field propagation features of the beams generated by these profiles, namely Flattened Gaussian beams (FGB).
InGaAs quantum-well-laser strain and temperature profile investigated by microprobe optical spectroscopy
Author(s):
M. Lugarà
Show Abstract
Strain and thermal characterization of the cladding layer in InGaAs ridge waveguide (RWG) lasers is reported. We tune up a photoluminescence micro-probe technique for determining the temperature and strain profile of the cladding layer, in steps of ∼1μm, with a temperature resolution <1°K. A correlation between the facet temperature and type of protective coating is found. A correlation has been obtained between the facet temperature and the laser oscillating mode. The experimental strain profile is well reproduced by an inclined line-force model.
On the counter-waves correlation in superradiance
Author(s):
Yu. A. Avetisyan
Show Abstract
The investigation of extended sample superradiance was performed by numerical solution of the semiclassical Maxwell-Bloch equations without using approximation of slowly varying (in space) amplitudes of electric field and medium polarization. The correlations of counter-propagating waves delay times and maximal intensities were analyzed.
Thick AlxGa1-xAs in GaAs/AlxGa1-xAs quantum wells: a leaky barrier
Author(s):
D. S. Kim
Show Abstract
The anomalously large Stokes and anti-Stokes real space charge transfer over thick barriers in GaAs/AlxGa1-xAs asymmetric double quantum wells (ADQW) in low temperature and low excitation limits has remained unsolved [1]. Here, we conclusively identify the inhomogeneity of the alloy barrier potential as the source of the Stokes transfer.
XeCl excimer laser with high repetition rate and low divergence beam
Author(s):
Yingzi Nan
Show Abstract
Configuration and performance of a high repetition rate XeCl excimer laser are reported. The laser maximum output energy is 415 mJ. Maximum average power is 35 W at repetition rate of 110 Hz. When unstable resonator optics are adopted on the laser. Beam divergence are improved about 10 times but expense of output energy in 30%.
Q switching of a diode laser pumped neodymium-doped yttrium lithium fluoride laser
Author(s):
Zhen Guo
Show Abstract
Diode laser pumping of solid-state lasers has been one the most signifieant developments in laser physies in recent years. Diode pumping offers high reliability, efficiency, and compacthess. These techniques have been applied to continuous-wave neodymium-doped yttrium lithium fluoride system. In this letter we report on the Q-switching of a diode laser pumped neodymium-doped yittrium lithium fluoride laser and have obtained pulses of 5Ons duration and peak power of 2KW at repetition rates 10KHz.
A new associated excitation mechanism for interstellar masers
Author(s):
Hanping Liu
Show Abstract
A new photo-excitation mechanism for masers of star-formation regions is presented, based upon the interaction between VUV photons and interstellar molecules. By using the mechanism, the unified interpretation of both H2O and OH masers can be argued, astronomical conditions can be satisfied.
Theoretical study of photonic band gap structures
Author(s):
D. Maystre
Show Abstract
Based on the analogy between Schrödinger and Helmholtz equations (or in other words between electron and photon), the concept of photonic crystal has been introduced very recently after an experimental evidence of the existence of transmission gaps in periodic dielectric structures used in the microwave region.. Due to the importance of photonic bad gap structures in practical applications such as inhibition of spontaneous emission in semi-conductor lasers, many experimental and theoretical efforts have been made in the last years in order to investigate the properties of photonic crystals, or to improve the construction of such structures in the visible region. Following a presentation of these structures, it will be shown that the electromagnetic theory is able to provide accurate predictions on the gaps, for both periodic and doped crystals.
Nonclassical properties of nonlinear light beam interactions
Author(s):
J. Peřina
Show Abstract
We investigate both codirectional and contradirectional nonlinear couplers composed of two nonlinear waveguides operating by second harmonic generation. We take into account possible mismatches inside the waveguides and between them. Quantum statistical characteristics, such as photon number distribution, its factorial moments, quadrature and integrated intensity vari- ances and quadrature uncertainty product can demonstrate effects of transmission of light between waveguides. Incident beams can be assumed to be coherent, squeezed and mixed with external noise. Second harmonic modes are assumed to be pumped with strong coherent beams. Nonclassical behavior of beams generated by the nonlinear waveguides can be transferred between them and controlled by linear and nonlinear mismatches. In the contradirectional regime of propagation asymptotic nonclassical states can be generated.
Quantum computation
Author(s):
Artur Ekert
Show Abstract
Quantum theory is vital for the next generation data processing devices. As computers become faster they must become smaller because of the finiteness of the speed of light. The history of computer technology has involved a sequence of changes from one type of physical realisation to another - from gears to relays to valves to transistors to integrated circuits and so on. The step to the molecular scale - the quantum level - will be next. Quantum theory is already important in the design of microelectronic components. Soon it will be necessary to harness quantum theory, rather than simply take it into account, to give data processing devices new functionality.
Resonant and nonresonant ultrafast processes in semiconductor doped glasses
Author(s):
Carlos H. Brito Cruz
Show Abstract
We review studies of resonant and nonresonant ultrafast optical processes in semiconductor doped glasses. First we discuss measurements done in CdTe quantum-dots in glass, excited resonantly. In this case we observe a fast recombination, that depends on the size of the quantum-dot. For the smallest dots, with 3.1 nm average radius, the recovery time constant was found to be 360 fs. Then we describe the observation of the Optical Stark shift in CdSxSe1-x semiconductor-doped glass (SDG) excited under nonresonant below gap condition. An ultrafast and pure light-induced shift of the band edge is observed. For a pump intensity of 3 GW/cm2 the band shifts by 11 meV. The time response of the shift tracks the profile of the pumping pulse.
New photorefractive ferroelectric for red and near infrared: tin hypothiodiphosphate
Author(s):
S. Odoulov
Show Abstract
At room temperature Tin hypothiodiphosphate (Sn2P2S6) belongs to spatial group Pc. The angle between its two optical axes is above 100°. The material is transparent from 0.53 to 8 μm with the bandgap close to 2.3 eV; it exhibits a pronounced photoconductivity. The crystallographic axis OX is nearly parallel to the axis of spontaneous polarization and the OY axis is normal to the mirror plane. Photorefractive recording inSn2P2S6 has been first accomplished in [1,2] with HeNe laser light. We report in this study on sensitizing of Sn2P2S6 crystals to cw-radiation of Nd3+:YAG laser (λ, = 1.06 μm) by pre-exposure to incoherent white light.
Lasing image and spectrum of two merging ink doped liquid microdroplets
Author(s):
Hee-Jong Moon
Show Abstract
Lasing images from two merging ink doped ethanol droplets (size ∼ 37 μm) generated by modulation techniques and pumped by nanosecond laser pulses, were photographed through a microscope. We observed lasing images from merging droplets in a variety of patterns. Noteworthy among these is the lasing from snowman-shaped droplets that are conjectured to stem from the coupled modes whose orbits round both droplets.
2A-CARS thermometry of hydrogen
Author(s):
W. Clauß
Show Abstract
The results of two-wavelength rotational CARS thermometry (2λ-CARS thermometry) of hydrogen at temperatures from 300 K to 1100 K are presented. Experimentally, temperature was measured in a heated cell using single-shot and averaged CARS intensities in the rotational S-branch. Relative standard deviation for single-shot temperature values was ∼1.5% at 296 K and ∼8% at 1000 K. The accuracy achieved, its dependence on measured temperature, and possibility of their improvement were analysed.
Vacuum effect and classical information on measured amplitude and phase
Author(s):
J. W. Noh
Show Abstract
In classical optics light is considered as an electromagnetic wave, and its dynamical properties are described by the time dependence of amplitude and phase. If a light emerging from a source has random fluctuation of amplitude and phase, this light can be described by a proper ensemble from which the mean and the dispersion of the dynamical variables are calculated. On the other hand, the same light beam can be also considered as a stream of photons in quantum optics, and the wave-particle duality produces nonclassical results in some cases. It is our purpose to clarify the role of wave and particle nature of light and distinguish the classical and quantum effects via the characterization of the dynamical variables when the light goes through a beamsplitter.
Two photon cooperative absorption and radiation of nonclassical light
Author(s):
N. A. Enaki
Show Abstract
The present report deals with the condition under which an ensemble of atoms goes over into a regime of collective two-photon nutation, and with the behavior of Rabi frequency as function of external light. To simplify this problem, we consider a system of Λ-type atoms that enters into two-photon resonance with an external squeezed electromagnetic field relative to the forbidden transition ∣1> ∣2> , where ∣1> and ∣2> are ground and first exited states [1,2] The situation is examining, when the values of quantum fluctuations of electromagnetic field intensity have the same value as the mean value of electromagnetic field intensity. This is one of main difference between the our paper and [2]. The proposed mathematical model permits to take into account all the two-photon diagrams. These diagrams describe not only resonance two-photon transitions but two-photon scattering processes between ∣1> and ∣2> levels too. Using mathematical method which is proposed in [1,2] it is obtained the master equation for the atom subsystem. Two stationary solutions for the case when Rabi frequency is larger than the inverse value of the collective two-photon decay time and the case when external light is coherent are examined. It is showing that the absorption rate of an phase squeezed field is larger than the absorption rate of an amplitude squeezed light. We also obtained the behavior of inversion between the levels ∣1> and ∣2>, when the collective of atoms enters into two-photon resonance with external field.
The use of phase conjugation in scanning laser microscopy
Author(s):
O. Nakamura
Show Abstract
We demonstrate two kinds of scanning laser microscopes which include phase conjugation. One is a 4 Pi confocal fluorescence/scattering microscope whose backward beam is generated with a phase conjugation mirror. The other is a double-pass absorption microscope in which a phase conjugation mirror is used. Both of the two scanning microscopes have advantages in small amount of aberrations and in freedom from precise alignment. Theoretical analysis of the imaging characteristics and several experiments with the two microscopes using cerium doped barium titanate crystal are shown.
Local field effect in the second harmonic generation spectra of Si surfaces
Author(s):
Bernardo S. Mendoza
Show Abstract
We calculate the SHG spectra of Si(100) and (111) surfaces taking account of the non-linear surface local field effect. Our model consists of four interpenetrated FCC lattices of bonds, each of which is centrosymmetric, but responds nonlinearly to the spatial inhomogeneities of the polarizing local field. The gradient of the field induced at a bond due to the dipole moment of a neighbor leads to a second order polarization which is canceled out in the bulk after summing over all other bonds, but it is not compensated at the surface, where it leads to a large nonlinear macroscopic response. Our model parameters are fitted to the nonlinear anisotropy measured at 1.17 and 2.34 eV. We calculate a linear anisotropy spectra for the (110) surface in agreement with experiment. Our nonlinear spectra shows peaks at 1.65 eV for a strained (100) surface and at 1.75 eV for a (111) surface, in agreement with recent experimental results.
Single mode optical parametric oscillator
Author(s):
F. Huisken
Show Abstract
Recent advances in new laser sources and new nonlinear crystals with a large nonlinearity and high damage threshold such as, e.g., KTP (KTiOP04), BBO (b-BaB204), LBO (LiB305) have renewed the interest in optical parametric oscillators (OPOs) [1]. For many applications the linewidth of the OPO is an important parameter. The problem of the OPO linewidth narrowing and early advances have been analysed in details in [2]. Recently, OPO operating on a single longitudinal mode using KTP as the nonlinear optical material and a grazing-incident-grating resonator was achived [3].
Generation of high-repetition rate visible fs-pulses by dispersive frequency doubling in lithium triborate
Author(s):
G. C. Cho
Show Abstract
The increasing demand of ultrashort laser system based on all solid-state concepts has stimulated he development of new solid-state laser material in the past. Both high peak power and broad spectrum are attractive for spectroscopic applications. By mixing intense laser pulses in nonlinear optical crystals ultrashort pulses from mid-infrared to ultra-violet have been generated. Optical parametric oscillators (OPO) driven by cw mode-locked Ti:sapphire laser provide a new source type of fs-pulses in the [tm wavelength range at high repetition rate.[1] Visible fs-pulses from all solid-state systems can therefore be generated by frequency doubling of OPO's.
Coherent tunable THz-wave generation from LiNbO3 optical parametric oscillator using a monolithick grating coupler
Author(s):
Kodo Kawase
Show Abstract
A couple of decades ago, the efficient and wide tunable THz wave generation had been reported by a group of Stanford Univ.1-3 based on both parametric and Raman effects. Although the interaction was highly efficient, most of the generated THz wave was absorbed or totally reflected inside the crystal due to a large absorption coefficient, as well as large refractive index (≈5.2 at THz range). They used a crystal one of whose corner was cut and polished at the proper angle to allow the signal radiation to emerge approximately normal to the exit surface.
Phase conjugator with femtosecond pulses
Author(s):
Hon-Fai Yau
Show Abstract
Self-Pumped Phase Conjugate signal with femtosecond laser pulse is observed. The pulse width of the incident laser pulses is about 126 femtosecond , the repetition rate is 110 MHz, and the wave-length is about 797 nm. The characters of the conjugate pulse are determined with an autocorrelator and a beam-profile analyzer. The quality of the conjugate pulses is found to be good by the well known phase distortion method.
Applications of bacteriorhodopsin films for optical modulation and logic operations
Author(s):
D. V. G. L. N. Rao
Show Abstract
Bacteriorhodopsin (bR) is the photodynamic protein complex found in the purple membrane of the Halobacterium halobium. The conformational changes of the bR molecule are associated with a photocycle. The initial B state of bR has an absorption peak at 570 nm while the long lived M state has an absorption peak at 412 nm. As the initial state has a broad absorption band it can be excited by means of red, yellow or green light. The M state can revert to the initial state via a thermal process or by a photochemical process by excitation with blue light. The lifetime of the M state can be dramatically altered by chemical and bioengineering methods. Several applications have already been proposed for bR as a photonic material.
Full optical characterization of highly nonlinear organic material, 3-Methyl-4-methoxy-4'-nitrostilbene(MMONS)
Author(s):
Hyung-Ki Hong
Show Abstract
Organic material 3-Methyl-4-methoxy-4'-nitrostilbene(MMONS) exhibits one of the largest powder second harmonic signals and has a great potential in frequency doubling and parametric conversion. The large second order nonlinear optical effect in this material attracts great interests because the phase shifts due to the second-order cascading effect can be utilized for the practical switching device.
First hyperpolarizabilities of weak organic acids
Author(s):
Paresh Chandra Ray
Show Abstract
Two limiting values for the first hyperpolarizability of three benzoic and three cinnamic acids in water, have been determined by the hyper-Rayleigh scattering technique at 1064 nm. The basic form of these organic acids has a higher value of molecular hyperpolarizability (βb) than the corresponding acidic form (βa). This is also confirmed by quantum chemical calculations.
Recent progress in quadratically enhanced optical nonlinear Langmuir-Blodgett multilayers
Author(s):
Shihong Ma
Show Abstract
A new type of bifat-chain amphiphilic molecules, 1,10-bisteary1-4,6,13,15-tetraene-18-nitrogencrown-6 (NC), was adopted as a spacer for an optically nonlinear hemicyanine derivative (HD) dye to form interleaving Y-type LB multilayers. The second harmonic (SH) intensity increased quadratically with the bilayer number up to 116 bilayers due to improvement of the structural properties by insertion of the long hydrophobic tail of the HD between two fat-chains of NC.
Terahertz radiation and ultrafast carrier dynamics in semi-insulating GaAs
Author(s):
Li Wang
Show Abstract
Terahertz (THz) far infrared radiation with a subpicosecond pulse duration is generated from an undoped semi-insulating GaAs (100) surface illuminated by femtosecond laser pulses. An anormalous enhancement of the THz emission is observed at room temperature when another pump pulse is used, which is attributed to the mobility increase resulted from carrier trapping by midgap defect levels, such as EL2 deep centers. An electron capture cross section of about 10-12 cm2 is estimated using this model.
Anisotropy of nonlinear absorption in a V3+:YAG crystal
Author(s):
N. N. Il'ichev
Show Abstract
Impurity-activated V3+:YAG crystals are used as passive laser switches in near-infrared lasers [1-3]. The phototropic properties of these crystals are due to the presence of wide additional-absorption (AA) bands with maxima near 0.8 and 1.3 μm. This additional absorption becomes saturated even at a low energy density of the incident radiation. For example, the absorption cross section for the λ≈1.3 pin band is ∝10-18 cm2 [2]. The AA bands are due to the V3+ ions in the YAG crystal matrix, which have the tetrahedral coordination of the garnet lattice ligands.
Laser beam self-channeling in a photorefractive waveguide
Author(s):
Alexei A. Kamshilin
Show Abstract
We report an experimental observation of the light beam self-channeling inside the photorefractive Bi12TiO20 waveguide-like sample. The phenomenon occurs when the strong fanning effect takes place. Total internal reflections of fanned beams from the waveguide surfaces and their coupling with the pump beam result in the light intensity redistribution inside the photorefractive waveguide. The self-induced channel of the increased light intensity speeds up the photorefractive energy exchange process.
Two orthogonally polarized optical solitons in fiber media with all higher order effects
Author(s):
P. K. Palanisamy
Show Abstract
We consider the Coupled Higher order Nonlinear Schrodinger (CHNLS) equations, which govern the propagation of two orthogonally polarized waves in a birefringent fiber with all the higher order effects. We generalize the 2×2 AKNS method to the 5×5 eigen valve problem and construct the Lax pair for the integrable form of CHNLS equation shown through Painlevé analysis. The exact soliton solutions are explicitly obtained using the Darboux-Bäcklund transformation.
Polarisation characteristics of two-photon absorption in LIF:F2- crystal at wavelength 1.06 um
Author(s):
T. T. Basiev
Show Abstract
The irreversible bleaching of F2⁻ color centers (CC) in a LiF crystal under influence of powerful IR radiation with wavelength 1.06 μm has been observed earlier [1]. It has been shown that F2⁻ CC bleaching is due to two-photon absorption from the excited state and results in the formation of a stable dichroic spatial band in the crystal. It has been shown [2-4] that F2⁻ CC irreversible bleaching is the reason of both spectral and polarisation "collapses" in Nd lasers with LiF:F2⁻ crystals as passive Q-switches.
Multi-conical emission at light counter-propagation in a resonant medium
Author(s):
A. A. Afanas'ev
Show Abstract
The counter-propagation of strong light beams in nonlinear media is capable to demonstrate a rich variety of spatio-temporal instability effects. Resonant media due to their spectral-selective and saturation properties enrich the nonlinear light dynamics which could result, for example, in an excitation of so-called conical emission manifested in a formation of far-field ring structure of resonantly scattered radiation. The cone frequency is usually shifted to a red side of the resonant transition while the pump beam frequency lies on a self-focusing blue wing. It has been shown analitycally [1] and numerically [2], that the conical emission appears mainly due to a frequency-shifted four-photon scattering (FPS) on Stark sublevels of the resonant system, and is excited inside of stable light filaments, which conclude a development of self-focusing frequency-degenerate spatial instability.
Properties of displaced idealized cat state
Author(s):
Zheng-Feng Hu
Show Abstract
The Schrödinger-cat state, the quantum-mechanical superposition of two coherent states, has been investigated extensively due to its many nonclassical features. The properties of Schrödinger-cat state highly depend on the overlap between the two coherent states, i.e. the interference of the two coherent states. It has been shown that the interference is determined by the phase. The schrödinger-cat state can also be consider as the superposition of two coherent states with the same amplitudes, but different phase. In contrast, the superposition of two coherent states with the same phases but different amplitudes will produce the phase-cat states.
Attractive interactions of vector dark solitons
Author(s):
Guang-Hoon Kim
Show Abstract
We investigate numerically the propagation properties of vector dark solitons. Two neighboring gray waves on the different background intensities attract strongly each other and form vector dark solitons. And the excessive energy forms another gray solitons.
Influence of laser radiation on the absorption of weak electromagnetic wave by free electrons in semiconductor superlattices
Author(s):
Nguyen Quang Bau
Show Abstract
The absorption of a weak electromagnetic wave by free electrons in semiconductor superlattices in the presence of a laser radiation (non-modulated and modulated) is discussed. The electron - acoustic phonon scattering is assume to be dominant. The analytic expression of the absorption coefficient is obtained. The dependence of the absorption coefficient on the temperature, the frequency and the superlattice parameters is analyzed. The dependence of the absorption coefficient on the time for the case of modulated laser radiation could allow to rise the deep penetration of laser radiation in superlattices.
Nonlinear refractive index measurment by modulation of probe beam interference pattern in a sample
Author(s):
M. T. Tavassolli
Show Abstract
In this work we report measurment of nonlinear refractive index of a glass plate doped with CdSxSe1-x microcrystallites by two new simple techniques. In the first technique, modulation of the inteference pattern produced by the reflected probe beam from the surfaces of the sample plate at the presence of the pump beam is exploited. In the second technique curvature change of the diffracted pump wave front, from the grating iduced by the inteference of the pump and probe, has been used.
A simple atom trap using frequency modulated diode laser
Author(s):
W. Jhe
Show Abstract
We have built a compact extended cavity diode laser system having microwave sidebands. Using the laser system, we could separate two stable isotopes of rubidium simultaneously trapped in a magneto-optical trap. We also have realized a very simple atom trap in a pyramid-shaped hollw mirror system and a conical hollow mirror using a single beam.
The DC magnetic fields generated by ultra-intense short laser pulse
Author(s):
Guihua Zeng
Show Abstract
The self-generated magnetic field induced by an ultra-intense short laser pulse in an uniform underdense plasma is investigated. A formulation for dc magnetic fields is derived. It is found that the dc magnetic fields strongly depend on the shape and group velocity of laser pulse. The magnetic field generation will be more effective in ultrashort pulse regime with higher plasma density.
Enhanced doubling of GaAlAs diode laser in LiIO3 crystal
Author(s):
Kwang Hoon Jeong
Show Abstract
The second harmonic of the 794 nm output of a GaAlAs diode laser is obtained in an external ring enhancement cavity. The dependence of the second harmonic power on the input power has been measured and compared with the theory. The second harmonic power of 4.2 μW at 397 nm has been obtained with an input fundamental power of 20 mW by using an 10-mm-long LiIO3 crystal.
Determination of spectroscopic parameters of non-linear absorbers by bleaching-effect dynamics analysis
Author(s):
Z. Mierczyk
Show Abstract
The paper presents the results of investigations of spectroscopic parameters of three saturable absorbers utilized in 1.06 ptm laser systems: foil with BDN dye, LiF with colour centers and YAG:Cr4+. The kinetics of absorber bleaching can be described by a two level quantum model. The nonsaturable component of the absorption coefficient, absorption cross-section, active centers concentration, excited state lifetime and energy consumed for bleaching effect have been estimated. Investigations of YAG:Cr4+ spectroscopic properties, and measurements of absorption and luminescence bands, allow the estimation of chromium ion concentration at particular charging state and positions in YAG crystalline structure and allow also to determine their mutual relations and influence of these relations on the non-linear properties of absorber.
Subpicosecond microwave pulse generation and measurement
Author(s):
Gangyao Xiao
Show Abstract
Recently, there has been a great deal of work on the generation of THz microwave radiation via excitation with ultrashort laser pulses. Modem integrated circuit technologies have made possible the precise fabrication of micron-sized dipoles which can radiate well into THz regime1,2 when photoconductively driven by subpicosecond laser pulses.
Steady-state intenstity of lasing with or without inversion in a simple three-level atomic system
Author(s):
Shang-qing Gong
Show Abstract
We, using a nonlinear theory of laser physics, investigate for a simple three-level atomic system the steady-state intensity behavior due to the effects of quantum coherence and decoherence. We find that the steady-state intensity of the laser field can arrive at a maximal value for a certain Rabi frequency of the driving field. We also find that the linear gain and the laser intensity tend to decrease for the linewidth of the driving field.
Fabry-Perot interferometer for the characterization of the linear electro-optic effect in polymeric films
Author(s):
J. H. Kim
Show Abstract
A model for transmission modulation is developed, and the experimental characterization of the Fabry-Perot interferometer with polymer thin film by tuning angles at a fixed wavelength is presented. Suitable approximations can be made to allow determination of the electro-optic coefficients of the spacer layer with polymeric materials. For this study, we made Fabry-Perot devices with thin polymeric films and metal mirrors, and measured the transmission-mode electro-optic characteristics.
Theoretical study on photon tunneling time in a frustrated total internal reflection structure
Author(s):
Byoungho Lee
Show Abstract
We calculated, for the first time, the tunneling time (phase time) and post-tunneling positions for TM photon tunneling in a frustrated total internal reflection (FTIR) structure. This is done by converting the TM photon tunneling problem in a FTIR structure to an electron tunneling problem for a heterostructure potential barrier with a position-dependent effective mass. The derived results are compared with FTIR tunneling cases of TE photons.
The one-dimension-short-range-potential model of high order harmonic generation (HOHG)
Author(s):
Xuexin Li
Show Abstract
By solving the One Dimension Short Range Potential Time Dependent Schrodinger Equation, the ionization probability,population of ground state and harmonic spectra of atom under different laser intensity are studied. It shows that the ionizatin of atom can enhance the harmonic generation, harmonic emission is generated from the jump of electron from continuum states to ground state,both the ionization and population are osscilating, but with different direction.
Intensity squeezing in semiconductor lasers
Author(s):
Tiancai Zhang
Show Abstract
Intensity squeezing is generated in single mode semiconductor laser by weak external mirror feedback. The measurable squeezing is 4.7%, corresponding to 9% below the SNL after correction for transmission and detection efficiency. It proves that intensity squeezing can be obtained at room temperature without line-narrowing techniques.
Chaos, phase singularities and spatial-temporal complexity in stimulated Brillouin scattering with weakly external feedback
Author(s):
Dong Sung Lim
Show Abstract
In this report we show the experimental observation and characterization of chaos in fundamental and generic nonlinear scattering process- Stimulated Brillouin scattering (SBS) in single mode optical fibers. Also presented is the experimental observation of spatial-temporal complexity and dynamically phase singularity formation in the transverse patterns of the Stokes emissions in multimode optical fibers. Preliminary results of theoretical analysis of these phenomena are presented.
Exact solution of coupled wave equations in degenerate four-wave mixing
Author(s):
M. Hosseini Farzad
Show Abstract
The coupled wave equations describing the optical phase conjugation by degenerate four wave mixing DFWM is usually, solved in the so called slowly varying amplitude approximation (SVA), where only the first derivatives of the amplitudes of the probe and of conjugate waves are taken into account. Here, we solve the coupled equations exactly for nonresonance ]interactions. This leads to an oscillatory dependence of reflectivity and of transmittance on the normalized coupling constant, κL. Also the intensity distributions of the probe and conjugate waves show oscillatory beat-like behaviors around the corresponding SWA distributions. The latter can be interpreted as the diffraction of the conjugate (probe) waves from the super-position of the pump-pump and pump-probe gratings.
Improvement of spatial beam profiles in beam combination using SBS mirrors
Author(s):
Y. S. Shin
Show Abstract
In the research of high power and high energy solid laser system and it's application, there are some traditional limits imposed by the maximum available volume of a single active medium.[1] These limits can arise from fundamental laser characteristics or they can arise from practical constraints of supporting technologies such as the limitation of crystal (laser active medium, e.g. Nd:YAG) growing, the increasing difficulty of cooling as the volume of laser medium grows, or so.
Theory of the optical radiation propagation in a DFB-structure with linearly changing period
Author(s):
A. A. Afanas'ev
Show Abstract
Some promising potential applications of DFB-structures stimulate interest of researchers in the 'radiation propagation problem in the case of periodically modulated media [1-3]. Of late years particular attention is payed to linear and nonlinear DFB-structures on the base of phase-shifted gratings and chirped ones [4,5]. Such DFB-structures exhibit quatatively novel characteristic properties and apt to find important use in integrated optics and quantum electronics.
Stimulated Raman scattering of femtosecond terawatt UV pulses
Author(s):
P. M. Mikheev
Show Abstract
Stimulated Raman Scattering (SRS) of nano- and picosecond light pulses in molecular gases is widely used for wavelength conversion, pulse shortening and other purposes [1]. For powerful femtosecond light pulses such non-linear phenomena as self- and crossmodulation, group velocity dispersion, etc. can strongly affect the quality of output stocks pulse. In this paper we analyse SRS of powerful femtosecond light pulses and show, that SRS could provide high-efficient conversion if the specific range of pulse and medium parameters is chosen. We also discuss the possibility of prepulse suppression and front edge sharpening that is extremely important for femtosecond-light-pulses-with-matter interaction.
Four-pass amplifier system with a stimulated Brillouin scattering mirror
Author(s):
J. R. Park
Show Abstract
Recently, in the field of high-power laser pulse generation many types of multipass amplifiers are proposed. The main reason of the use of such amplifiers is that energy extraction efficiency from a gain medium can be increased with the number of passes through the medium. However in the course of amplification, the wavefront aberration and polarization distortion of a laser pulse are also increased by the active medium.[1][2]
Preferred values and dispersions of phase of any order for l-photon Kerr states
Author(s):
V. Peřinová
Show Abstract
It is well known that during the ℓth-subharmonic generation general ℓ-photon states evolve from an arbitrary state of the pump mode. For the second-subharmonic generation with an initial coherent state the assumption of pump nondepletion, the so called parametric approximation, is very useful for obtaining closed formulas. The resulting state then is an ordinary squeezed vacuum. The parametric approximation is ineffective for ℓ > 2 not only because closed formulas are not obtained, but also because it is proven that no quantum state is defined for nonzero higher-order squeezing [1]. This finding motivated a definition of the ℓ-photon coherent state [2],
Growth mechanism and optical properties of a new nitroaromatic compound
Author(s):
Kang I. Seo
Show Abstract
The new organic compound, mixed methyl-(2,4- dinitropheny1)-aminopropanoate: 2-methyl-4-nitroaniline, was used for growth of thin films by organic molecular beam deposition (OMBD) technique. We measured the refractive index using the prism coupler method. Scanning electron microscopy, infrared spectroscopy, and x-ray diffraction are used to observe the morphological features, the chemical structures, and the orientation, respectively.
Nd:glass laser with a phase conjugating mirror based on SBS
Author(s):
H. S. Kim
Show Abstract
Recently, lasers and amplifiers have been developed to obtain a good spatial profile of a laser beam since good beam quality has been required for the best experimental results in many areas.1,2 Stimulated Brillouin scattering (SBS) is one of the strong candidates to realize a laser or an amplifier with good beam quality.2 The application of SBS in laser systems has been suggested to compensate for phase distortion and to achieve a stable beam quality. One of application is a phase conjugated laser oscillator.3
Femtosecond degenerate four-wave mixing in 350 um undoped and n-type InP due to virtual third-order polarization
Author(s):
Sungkyu Yu
Show Abstract
We performed femtosecond two-beam self-diffracted four-wave mixing (FWM) experiment[1,2] in 350 μm undoped and n-type InP at 10 K using a self-modelocked Ti:sapphire laser under below the band gap excitation condition where no absorption occurs. We found strong FWM signal even though no real population is created. Fig. 1 shows the spectrally resolved (SR) FWM signal for 350 μm undoped (a) and n-type (b) at below the band gap of 1.3328 eV (approximate band gap of an undoped InP is 1.41 eV) as a function of time delay T. The excitation laser spectrum is shown as broken line.
Optical rectification in absorption bands of optically active liquids: application to a three-level model
Author(s):
S. Woźniak
Show Abstract
A molecular approach to optical rectification (OR) via the imaginary part of the second-order susceptibility related to electric dipole interaction with the radiation field is presented. A general quantum-mechanical expression for the frequency dependence of the effect is obtained, its properties are discussed and its magnitude is estimated in absorption bands of a three-level model.
The spectral perturbation method
Author(s):
V. A. Vysloukh
Show Abstract
We develope the Spectral Perturbation Method. We obtain an irrestricted quantitative estimation of the frequency shift in terms of the soliton and the Raman line parameters. Computer simulations confirm our analytical results.
Light-hole and heavy-hole exciton dynamics in GaAs/AlGaAs multiple quantum wells
Author(s):
Joo In Lee
Show Abstract
Exciton dynamics in quantum wells have been much investigated by using the time-resolved spectroscopic methods for understanding of physical phenomena and possible device applications. Only heavy-hole (hh) exciton dynamics, however, has been of concern to many scientists. We expected that light-hole (lh) exciton in addition to hh exciton provides important information on the exciton dynamics. To our knowledge, we report for the first time the dynamics of lh exciton as well as hh exciton in GaAs/A1GaAs 120 Å and 150 Å multiple quantum wells (MQW). We observed that light-hole exciton has a longer decay time than heavy-hole exciton, which results from the difference of the exciton population factor. We considered the thermal population time to explain the observed exciton dynamics.
Micromaser with atomic coherence
Author(s):
Camilo A. Arancibia-Bulnes
Show Abstract
We study the effects produced by atomic coherence in a lossless micromaser. It is shown that a coherent field may be achieved from a thermal photon distribution.
Interrelation between non-linear optical properties and structure-topological order in ternary Ce-As-S glasses
Author(s):
Istvan Fekeshgazi
Show Abstract
Chalcogenide glasses are promising materials for production of different optical elements for integral and optoelectronics and laser devices. Generally it is due to the properties of the glasses that are transparent in visible and TR region of spectrum and posses different values of refractive indices and relatively low optical and acuostooptical losses. However, their relatively low damage threshold is the main restriction for their wide application. As it is known the damage threshold of a material is mostly defined by linear and nonlinear losses of laser radiation. The dependencies of linear losses coefficients α, two-photon absorption constant β, optical damage threshold Ip and pseudogap width Eo on component concentration x and average coordination number values r of ternary chalcogenide semiconductive glasses of Ge-As-S system have been experimentally determined by investigation of the high intensity dependencies of transmission of the ruby laser light emission.
Phase hologram formation dynamics for dichromated gelatin film
Author(s):
Yeung Lak Lee
Show Abstract
Time-dependent diffraction efficiency is measured during hologram formations in a dichromated gelatin film. It is observed that the refractive index modulation is strong nonlinear with exposure time. In order to explain the complicated hologram formation dynamics, we present a phenomenological model for photoinduced refractive index changes by assuming that two photochemical reaction centers are responsible for the hologram formations.
Nonclassical spatial properties of light propagation in a x(2) materials
Author(s):
M. De Angelis
Show Abstract
We have studied quantum effects in a system governed by the spatial nonlinear Schrodinger equation derived for a two beams interaction in a quadratic nonlinear material. For a quadratic nonlinear material it has recently been demonstrated [2, 3] that, under suitable conditions, in the interaction between the fundamental and the second harmonic field, the fundamental field propagation can be described as a solution of a nonlinear Schroedinger equation, given in terms of spatial solitons [4,5]. In this work we are interested at the quantum properties of the fundamental beam in this kind of interaction. We use a quantum field description [1] where the spatial variable of propagation z plays the role of time in the standard quantum theory, and we apply it to the case of a strong plane wave that can be described as a classical field propagating through the nonlinear medium in the z-direction. We assume TE polarizations for all the monochromatics fields involved into the interaction in a type I material.
Stimulated Raman scattering spectra: quantum fluctuations and time evolution of linewidth
Author(s):
V. G. Bespalov
Show Abstract
Manifestations of quantum fluctuations in stimulated Raman scattering ( SRS ) have been intensively studied lately1. Quantum noise present in spontaneous scattering stimulates fluctuations both in phase and in amplitude characteristics of output Stokes emission. At present statistical properties of amplitude fluctuations are studied in detail and it is shown that in linear transient regime of SRS without pump depletion statistical scatter of Stokes energy Es has negative exponential distribution2. In saturation regime of SRS the amplitude fluctuations are almost suppressed simultaneously with pump depletion. The phase fluctuations manifest both in linear and in nonlinear SRS and produce beam pointing fluctuations3, a change in Stokes emission spectra from pulse to pulse4 and cause soliton appearance in Rayleigh component of SRS5. Phase noise is observed in saturation regime due to relation between phases of Stokes and phonon waves which is preserved in processes of stationary and quasistationary SRS amplification. Spectrum phase fluctuations manifest as fine structure of SRS spectrum4, fluctuations of average Stokes frequency and Stokes linewidth fluctuations. The evolution of phase fluctuations in time is determined by the nature of spontaneous scattering and polarization of Raman media and is of great interest as one can follow its development from vacuum modes level to saturation regime. However up to now this problem has not been studied yet.
Relaxation dynamics of photoexcitation in MEH-PPV and CNMBC blending polymer
Author(s):
Hyo Soon Eom
Show Abstract
Conjugated polymers have attracted considerable attention as quasi-one dimensional semiconductors owing to easily tunable optical and electronic properties. One of the exciting examples is the development of electroluminescent devices based on PPV (poly 1,4-phenylenevinylene). A thorough understanding of photogeneration of carriers and energy transfer mechanism, however, is needed to have futher information on the mechanism of eletroluminescence and enhance the performance of LED devices.
Characteristics of on-off intermittency in a q-switched Nd:YAG laser
Author(s):
Chil-Min Kim
Show Abstract
We observe on-off intermittency in a Q-switched Nd:YAG laser. When the laser current is low enough, before laser is off, the intermittency appears at high switching frequency. The characteristics of the phenomenon at 20 kHz of switching frequency is analyzed by the average laminar lengths according to the discharge current.
Analysis of z-scan technique in photorefractive crystals
Author(s):
Shaoping Bian
Show Abstract
The far-field diffraction pattern of a photorefractive crystal under an external applied electric field in a Z-scan configuration is derived based on the analysis of the propagation of a Gaussian beam wavefront with spatial phase distortion. The effective electro-optic coefficient of a SBN:Ce crystal is determined from the Z-scan experiments. Enhanced sensitivity is predicted if the light irradiance is measured at the ofd axis positions in the far field.
A partial coherence resonance fluorescence analysis
Author(s):
J. J. Sanchez-Mondragón
Show Abstract
We present the resonance fluorescence spectrum produced by a partially coherent external field, described by its even order correlation. We discuss CW [1] partial coherence but the procedure is suitable for pulse excitation beams where most of recent experimental interest has arised. In our analysis we consider an stochastic driving field and the semiclassical theory of radiation in a two level atom[2].
Femtosecond nonlinearity due to virtual excitation in thick bulk GaAs
Author(s):
D. S. Kim
Show Abstract
We performed femtosecond degenerate four-wave mixing (FWM) experiments at 10 K and at relatively low intensity (100 fs, 0.1 nJ per pulse focused into 200 micron spot) in thick GaAs (500 micron), exciting
completely below the band gap (up to 200 meV) where no absorption occurs (Fig. 1a). We found rather strong FWM signal (much stronger than the resonant excitonic signal of etched GaAs or GaAs quantum wells of ∼1 micron thickness) even though no real population is created. Most interesting observations we made are summarized as follows:
(1) The time-integrated (TI) FWM signal
always peaks at negative time delay (Fig. 1b).
(2) The signal decreases rapidly as the detuning increases, approximately as (detuning)
-6 (Fig. 2a).
(3) There exists very fast pump-probe signal even when the laser is tuned completely below the band gap (Fig. 2b).
To understand our results, we performed first principle calculations. It is shown that virtual excitation is responsible for the observed signal.
Reflection-grating photorefractive double phase-conjugate mirror
Author(s):
Won B. Roh
Show Abstract
A reflection-grating double phase-conjugate mirror (RG-DPCM) has been demonstrated for the first time in a photorefractive medium. The device was realized with a rhodium-doped barium titanate crystal using a Kr-ion laser at 647 nrit The performance characteristics of the mirror, including the measured transmittance and reflectance, are presented and compared with the theoretical predictions.
Snake-effect soliton demultiplexer
Author(s):
F. Garzia
Show Abstract
A device capable of addressing an input pulse through different outputs is presented. The controlling parameter is the power of the input beam. The device is characterized by a 100% transferring efficiency and a short switching time.
Anomalous skin effect in laser plasma interaction with ultrashort pulse
Author(s):
Guobin Ma
Show Abstract
The importance of studying skin effect in laser plasma interaction has been increased by the development of intense subpicosecond laser technology in recent years. Here we present a new method based on Fourier transformation to study the normal and anomalous skin effect.
Instability of high-power light field in dielectric microsphere
Author(s):
Vitali E. Grouzdev
Show Abstract
A model to describe localization of high-power electromagnetic field and abrupt increasing its amplitude in nonabsorbing dielectric inclusion in transparent medium is presented. It is based on formation of unstable field structure in dielectric microsphere. Possibility for field instability to arise is estimated making use of model of diffraction of high-amplitude plane wave on sphere which radius is about radiation wavelength. There are estimated threshold amplitude of incident wave and field amplification in microsphere. Physical reason for the instability to develop is considered and shown to be connected with formation of positive feedback arising with light-induced formation of microsphere's eigenmodes.
Electrical field distribution in a microstrip traveling wave Pockels cell
Author(s):
Dalwoo Kim
Show Abstract
Modem optoelectrionics has made it possible to obtain electrical pulse of picoseconds or even subpicoseconds which is beyond the available dynamic range of any normal electronic detection method. One of the solution is electro-optic sampling which uses a microstrip Pockels cell to determine the electrical pulse waveform1,2. When the ultrashort electrical pulse propagates along the stripline of the Pockels cell, the electrical field inside the electro-optic crystal modulates the sampling light beam which enables us to obtain the time variance of the electrical field. Generally, the electrical field in the Pockels cell is assumed to be homogeneous. This approximation is reasonable for a macro Pockels cell, but cannot be applied to a microstrip Pockels cell. In this paper, we studied the electrical field distribution in a microstrip traveling wave Pockels cell.
New results in the theory of optically heterodyned polarization interferometry of polarization inhomogeneous media
Author(s):
I. I. Gancheryonok
Show Abstract
We present consistent theoretical studies of the optically heterodyned polarization interferometry (OHPI) of polarization inhomogeneous media (initially isotropic materials) with collinear arbitrary polarized (partially or totally depolarized) interacting beams (pump-probe scheme) within the framework of the 3rd-order nonlinear susceptibility. We have built our calculation of a signal behind the analyzer within the framework of Mueller matrix and Stokes vector formalism. Such an approach allows to take into account the possible depolarization of the interacting waves in the optical canals of the measuring scheme. We shall follow the notations and the principles of the theoretical treatment presented in paper [1].
Progress in ultrafast optoelectronics
Author(s):
Takeshi Kamiya
Show Abstract
The reason why optoelectronic is one of the most promising technologies for future information society lies in the potential of high density packing of photons in time, frequency or space domains. This feature already is proven by the success of fiber optic telecommunication or by high density optical disc storage. The ultimate performance restricted by the physical principle, however, is yet to come (1)(2). Specifically in time domain, the fruits of scientific researches on femtosecond laser pulses(3) are not yet fully exploited in information technologies. In Japan a considerable amount of efforts have been paid on the basic study of ultrafast optics, such as the university joint research program (4), or government-industrial research consortium entitled "femtosecond technology"(5).
The present review emphasizes the hardware aspects of the recent progress in ultrafast optoelectronics and touches also some of the future prospect on application fields.
Glass integrated optics: advances and perspectives
Author(s):
Giancarlo C. Righini
Show Abstract
After several years of research in the laboratories, glass integrated optics is now emerging as an area with industrial relevance, and several devices are already available commercially. Silica-on-silicon integrated optical circuits are particularly attractive, as they represent a key technology for the development of both the passive and the active optical components required for the next generation of fiber optic communication systems. Great expectancy exists for all-optical devices that exploit the nonlinear optical properties of novel glasses or glass-based composite materials. This paper reviews recent progress on glass integrated optics, with particular focus on semiconductor-doped and rare-earth-doped glasses.
Time-and-space-domain holography in frequency-selective spectral hole burning materials
Author(s):
Alexander Rebane
Show Abstract
Time-and-space-domain holography [1,2] can be regarded as an extension of a conventional holographic process, where, in addition to the spatial image, the hologram plays back the time dependence of an event. The play-back of events is possible because we are using highly frequency-selective inhomogeneously broadened absorbers as recording material. This technique has a variety of potential applications in optical data storage and processing. In the present paper we consider the basic physical principle of time-and-space-domain storage in frequency-selective materials which exploit the effect of spectral hole burning [3]. In particular we will show that organic dye-doped spectral hole burning materials allow recording and playback of pi- co- and femtosecond time-scale events.
Optoelectronic morphological processors
Author(s):
Tomasz Szoplik
Show Abstract
Nonlinear rank order and mathematical morphology techniques of digital image processing can be implemented in optical-digital processors. Threshold decomposition of gray scale images, stacking property of rank order filters, commutability of rank order operations with thresholding, and optical-digital method of local histogram calculation constitute basic concepts due to which optoelectronic implementations of rank order and morphological filters is possible. In those hybrid processors, the convolutions are performed in inherently parallel optical correlators while arithmetic and logic operations are made digitally. Sequential morphological filters and rank order algorithms are constructed by looping of intermediate results, what is possible on different data flow stages. Recent configurations of optical convolvers are recalled and future prospects of hybrid morphological processors are discussed.
Dispersion characteristics of proton exchanged LiNbO3 optical waveguides
Author(s):
L. P. Shi
Show Abstract
Planar optical waveguides in z-cut LiNbO3 (LN) substrates have been fabricated using the proton-exchange(PE) process. The effective refractive indices of different guided modes before and after annealing were measured at different wavelengths. The dispersion characteristics of the effective refractive indices can be described by a sellmeier-like equation, and there is an excellent agreement between the measured data and the values calculated using the equation.
Electro-optic effects in organic/silica hybrid film and fabrication of channel waveguide
Author(s):
Yoo Hong Min
Show Abstract
Inorganic polymer system where organic chromophores with large nonlinear optical coefficients are chemically bonded to silica matrix has been paid a great attention as a novel electro-optic material. Organic/silica hybrid thin film has many advantages over the organic polymer systems; such as low optical propagation loss, temporal stability, chemical and mechanical stabilities. In this paper the optical properties of organic/silica composite film and the fabrication of a single mode chaimel waveguide will be presented.
Permanent associative memory using quadric hologram based static phase conjugate mirror
Author(s):
P. V. Polvanskii
Show Abstract
New version of an all-optical associative memory is presented The recording of a static hologram in the arrangement of a four-wave degenerate mixing is pre-supposed. If an amplitude response of such a hologram contains the components of a power series expansion on exposure degrees up to the quadratic one, then the hologram shows auto- and heteroassociative properties into self-conjugating regime. Error-correcting features of the proposed associative memory are discussed.
Depolarization effects due to pregrooves on magneto-optical disks
Author(s):
W. G. Ophey
Show Abstract
This note describes the effect of disk pregrooves on the Magneto-Optical read-out. The pregrooves give rise to a depolarization of the diffracted beams and affect the MO read-out. The presence of the depolarization effect can be shown both by calculations and experiments.
Optical storage of information via refreshing by inverse seeding (OSIRIS)
Author(s):
M. Esselbach
Show Abstract
We show a possibility of realizing an optical memory using dynamic refreshment. Via phase-correct back-coupling by means of nonlinear optical phase-conjugation the information stored in a photorefractive crystal is periodically read out, transmitted into a second crystal acting as an auxiliary memory and from this transmitted back into the first crystal. In this way the information is refreshed.
Study on dynamics of persistent spectral hole formation in frequency domain optical storage
Author(s):
You-yuan Zhao
Show Abstract
A variety of studies on persistent spectral hole burning (PSHB) have been carried out for the last twenty years [1.2.3], since the discovery of this phenomena in 1974. The elucidation of electron-phonon interaction, the nature of zero-phonon line and spectral diffusion in PSHB have been studied intensively together with the research aiming at its possible applicability to ultra-high density optical information storage in frequency domain.
Photoelectric properties in Al/tin-phthalocyanine(SnPc)/ITO sandwich cell
Author(s):
Yongle Pan
Show Abstract
Thin films of crystalline organic materials have attracted increasing attention in recent years due to their important photoelectric properties and particular advantages as compared with the inorganic functional materials[) 1. In this paper, we report the transient and steady-state photoelectric properties of the relatively less-investigated Al/α-SnPc/ITO sandwich cell. It may offers a potential application in the area of light-controlled nonlinear optoelctronic devices. Electric modulation reflective spectroscopy(ER) shows higher sensitivity than the conventional spectroscopies in the detection of charge-transfer(CT) exciton, which may play an important rule in the formation of photoelectric properties as well as the Frenkel exciton in the SnPc film.
Photovoltaic edge-effect in planar GaAs MESFETs
Author(s):
D. Abbott
Show Abstract
A significant new internal gain effect, in planar MESFETs has been discovered which we call the "photovoltaic self-biasing edge-effect." The edge-effect can be exploited to attain up to a factor of ten improvement in detector photosensitivity.
Wavelength tunable optical isolator possessing linear birefringence
Author(s):
Sang Yeon Cho
Show Abstract
Isolation performance of a tunable optical isolator possessing linear birefringence is analyzed. More accurate adjustments in output polarizer angle and in Faraday rotation angle are required for the birefringent tunable optical isolator, that is, the range of the adjustment angles to tune the birefringent isolator (δ = 0.5 degree) for isolation > 50dB at 840nm is 53% narrower than the birefringenceless isolator.
Regeneration of optical signals by fiber logic elements operating through stimulated Raman scattering
Author(s):
E. A. Kuzin
Show Abstract
A regenerator is a key element in the long haul fiber communication systems. It must preserve the contrast between the pulses corresponding to logic ones and zeroes, and the high enough level of the logic ones, as well as to restore them to their position on the pulse sequence. In order to solve these problems, nonlinear optical elements are used. Those elements based on nonlinear phenomena in fibers are preferred due to their high pulse repetition frequency operation. Recently elements based on the SRS were used for regeneration of the optical signals [1]. Here, we discuss the possibility of using a SRS element to regenerate short pulses at the presence of their walk-off.
Speckle reduction in laser projection systems
Author(s):
L. L. Wang
Show Abstract
In laser projection systems the observer in the far field of the image points of the screen will recognize serious speckle noise. There are many methods to reduce or eliminate speckles in the near field, by reducing or eliminating spatial or temporal coherence of the laser. But for far field, it is hardly possible to change coherence properties of laser sources. In this paper we propose a new method to eliminate speckles in the far field by using diffractive optical elements. Intensity modulation depth in the far field speckle pattern could be reduced to a few percent with keeping good beam quality.
Video-rate simulated annealing for early vision tasks
Author(s):
D. Prévost
Show Abstract
We describe a massively parallel system that uses speckle patterns projected onto a dedicated integrated circuit to carry out Monte Carlo computations at video-rate on a locally interconnected mesh of binary state variables.
All-optical reduced state 4 x 4 switch
Author(s):
Dan M. Marom
Show Abstract
Multistage interconnection networks (MIN) are a class of switching structures for interconnecting an input array to an output array. Traditionally, they have been implemented in a planar configuration, suitable for electronics. Optical interconnection technology applied to MINs has been suggested in the last decade. Most of the proposed implementations propose replacing the fixed interconnection pattern between switching stages by optical interconnects.
Low temperature consolidation of flame-hydrolysis-deposited silica layer for integrated optics application
Author(s):
Yong Tae Lee
Show Abstract
A flame-hydrolysis-deposited silica layer is produced and consolidated at low temperature as 850°C. The concentration of boron oxide in the layer is measured to be 13∼15 mole %. Such a low temperature consolidation process of the flame hydrolysis deposition (FHD) layer allows hybridization between the RID and chemical vapor deposition (CVD) method. For example, a CVD phosphosilicate waveguide is covered with the FHD highly-boron-doped silica layer and its properties are examined. The upper cladding (to 24 μm) is successfully deposited in one step and showed good filling capability of the gap between the waveguides. The refractive index of this layer is low (1.453) compared to that of the high pressure steam oxide (1.457). Insertion loss of the 32 mm long sample annealed at 1000°C is 1.13 dB and the propagation loss is estimated as 0.1 dB/cm or better.
Electro-optic characteristics of Pc LB films aligned liquid crystal cells
Author(s):
Ruibo Lu
Show Abstract
Uniform and orderly liquid crystal (LC) alipment is an important technology in liquid crystal display (LCD) devices. In recent years, there is a trend of using Langmuir-Blodgett (LB) technique to fabricate ultra-thin and controllable LB films as LC aliening layers. Here, we adopted a series of metal phthalocyanine (Pc) complex LB films to align nematic LC ZLI--1132 and mainly investigated their electro-optic characteristics of the corresponding antiparallel (AP) type, twisted nematic (TN) type and hybrid-aligned nematic (HAN) type LC cells using a He-Ne laser as the light source.
Propagation characteristics of chiral grating waveguides
Author(s):
Keiji Matsumoto
Show Abstract
A rigorous analysis of guided waves in chiral grating waveguides is presented. The numerical examples clarify that peculiar stop bands and leaky waves appear owing to the chirality and periodicity of the medium.
Research and developments of several SLMs
Author(s):
Yulin Li
Show Abstract
In this paper, we will introduce some of SLMs research and applications in our laboratory, mainly the Liquid Crystal Light Valve(LCLV), CRT-LCLV and photorefractive crystal devices and their application.
Light emitting devices made with polymer blend
Author(s):
Taehyoung Zyung
Show Abstract
We report the polymer light emitting device with high quantum efficiency of electroluminescence made with the polymer blend. The quantum efficiency increases with the composition ratio of one component polymer up to about 500 times of the quantum efficiency of the other polymer.
The memory effect in photothermoplastic medium during interferogram and color image recording
Author(s):
Igor V. Chapurin
Show Abstract
The regularities of information recording on photothermoplastic media by cyclicaly interrupted charges and expositions of warmed media was examined. In this method the complex harmonical relief is formed by recording of new images on the surface relief, which had been formed earlier. The diffraction efficiency of recorded color images is not less than 6= in every of color coding channel and not less than 10= in case of two-exposition interferogrames recording.
Estimation of optical turbulence profiles using SCIDAR
Author(s):
J. C. Dainty
Show Abstract
The technique of SCIDAR (SClintillation Detection And Ranging) was first suggested by Rocca et al[1] and has since been developed extensively by Vernin and colleagues[2],[3],[4],[5]. The idea is based upon two premises: (i) that the value of the refractive index structure constant Cn2(h) for a layer of turbulence at altitude h can be estimated from the variance of the scintillation received at the pupil of a telescope, and (ii) that layers can be identified using a triagulation technique based on recording the spatial correlation function of the scintillation from a double star of angular separation α, the height h of the layer being equivalent to the autocorrelation lag δx/α. Because the variance of the scintillation scales as h5/3, it is not possible to measure Cn2(h) for h=0, i.e. in the pupil itself using SCIDAR. Recently, Fuchs et al [6] have extended the idea to the case where one records scintillation in a plane defocussed from the pupil plane, coining the term Generalised SCIDAR for this case, in which it is now possible to record Cn2(h) in the pupil. By measuring the spatio-temporal correlation for light from a single star, the velocities of the dominant layers can also be estimated.
Correction of aerosol optical parameters on DIAL ozone measurement
Author(s):
Chan Bong Park
Show Abstract
DIAL (Differential Absorption Lidars) method is being used as one of the most effective method to reduce the interference error from air density and aerosol in ozone measurement. But according to the selection of each wavelength, the optical parameters are much variable, and it sometimes bring the great error of ozone concentration. Especially aerosol optical parameters are strongly affected by the kinds and the concentration in stratosphere and troposphere[1,2].
Optical probing of the atmospheric boundary layer using lidar
Author(s):
P. Ernest Raj
Show Abstract
The field of optical remote sensing of the atmosphere has advanced greatly with the advent of lasers. Laser remote sensors form a special class of optical remote sensors. The physics and optical technology associated with atmospheric laser remote sensing encompass atmospheric optical propagation, atomic and molecular spectroscopy, digital signal processing and laser technology.
Simulation calculation and theoretical analysis of an adaptive optics system and light propagation in the atmosphere
Author(s):
Deliang Zhang
Show Abstract
An adaptive optics(AO) system can apply a real time compensation to light wavefront distortion, so it plays an important part in imaging through the atmosphere, such as astronomical observation. When light propagates through the atmosphere, the atmospheric turbulence induces wave-front distortion of the light, so it is very important to investigate the AO system and light propagation in the atmosphere together. By mean of simulation calculation and theoretical analysis, it is far more inexpensive to investigate performance of an AO system under various conditions. And the most important thing is that by means of these works, we can clearly understand the effect of each part of an AO system, as well as its whole effect. Then we can enhance the compensate capability of an AO system more efficiently.
The limiting possibilities of the satellite laser ranging
Author(s):
V. I. Prokhorenko
Show Abstract
Optical effects restricting the limiting accuracy of the laser ranging of the satellites analyzed. The most important are the disperse blur of ultrashort pulses in the atmosphere and the effect of the transverse group delay. These effects cause the limitation of the distance measurement accuracy ( per one shot ) by 1 - 5 millimeters depending of the orbit high. Accuracy of two-frequency ranging method is also discussed. It is show that the attainable limiting accuracy is about several millimeters even for the low orbit satellites.
High resolution wavefront correction in a LCLV-based system with a phase knife in the optical feedback loop
Author(s):
A. V. Larichev
Show Abstract
Conventional adaptive systems, whose key elements are wavefront sensor and electro-mechanical wavefront corrector, face considerable difficulties, when high-order aberrations correction is required. The increase of number of adaptive mirror's control elements (up to several hundreds, recently) inevitably leads to the sophistication of the sensor for measuring the wavefront "fine structure" and to intensive computations at the stage of wavefront reconstruction. Therefore, new, controlling light by light, techniques, which do not violate the distributed nature of light wave, attract attention of researchers [1, 2, 3]. There are a number of optically controllable hybrid devices (for example, microchannel modulator [1], liquid crystal light valve (LCLV) [2], and membrane mirror [3]) that may be used for distributed wavefront correction. However, adequate control methods for such correctors should be developed.
Adaptive forming beams and images simulation through the atmosphere
Author(s):
Vladimir P. Lukin
Show Abstract
In recent years much progress has been reached in developing wave front sensors and correctors and then fitting the optical facilities operating under atmospheric distortions with these devices. In this connection an increased interest of researchers is observed to the theoretical works concerning with selection of an optical design and configuration of the wave front corrections.
The effects of the wavefront dislocations on the atmospheric adaptive optical systems performance
Author(s):
Boris V. Fortes
Show Abstract
A phenomenon of the wavefront dislocations of the optical irradiance propagating through the turbulent atmosphere and for the thermal blooming of a high-power beam is considered. Using the numerical simulation method, the effects of the wavefront dislocations on the adaptive optical system performance have been investigated. We have found a connection between instability of the phase conjugation efficiency and the reference wavefront dislocations.
High resolution imaging with reference to a widely separated star
Author(s):
Naoshi Baba
Show Abstract
It is shown that high resolution imaging is possible by use of a reference star that is separated wider than the isoplanatic angle from an object under observation. A shift-and-add operation to the reference star results in a high resolution image of an object, though not diffraction-limited. Observational results of a binary star with angular separation of 22" indicate that a simple adaptive optics system is feasible in the visible region.
Simulation of adaptive optical systems
Author(s):
Robert G. Muharliamov
Show Abstract
A problem of simulation for an adaptive optical system realized as a discrete mirror consisted of a finite number of identical elements is solved. Discrete mirrors element is considered as a nonsymmetrique rigid body, the position of which is defined by six generalized coordinates. The control is realized by three paralleles forces applied in fixed points of element or by forces, acting along directions giving in the immobile space. The purpose of control is a displacement of mirrors elements in accordance with variation of wave front set. The method of construction of dynamics equations of the discrete mirrors element as a mechanical system with programmed constraints and corresponding discretization schemes hence forth are recommended.
Infrared adaptive optical system of the 2.16 meter telescope and its wavefront detecting error and performance analysis
Author(s):
Wenhan Jiang
Show Abstract
A 21-element adaptive optical system[1] has been built and installed at the 2.16 meter telescope of Beijing Astronomical Observatory. It consists of a pair of photon counting shearing interferometers as the wavefront detector, a 21-element deformable mirror and a fast steering mirror as the wavefront correctors, a digital processor for computing the phase angles from the photon counts of the shearing interferometers and wavefront reconstruction and control algorithm, 23 channels of high voltage amplifier. The wavefront error sensing is in the visible wavelength and the compensated images are detected in infrared (2.2 mm) by a Pt Si CCD camera offered by the National Observatory of Japan. The installation of the adaptive optics system and the experimental observation in visible wavelength have been completed. Due to delay in development of IR CCD, observation in IR wavelength has not been completed yet. In this paper, the system and its preliminary observation results will be briefly reported. Fig. 1 shows the images of a binary star (SAO 99587) in visible wavelength with and without correction.
Autocorrelation estimate in non-linear image detectors using an auxiliary photomultiplier: error analysis
Author(s):
M. P. Cagigal
Show Abstract
In an experiment in which two or more photoevents arriving at the same pixel are considered as a single count, a one-pixel-size central hole appears in the autocorrelation estimate. This hole is a source of error when high resolution techniques based on the autocorrelation function measurement are applied to image or signal recovery.
This contribution analyze a previously proposed experimental method to evaluate t1e autocorrelation central hole using an image detector and an auxiliary photomultiplier. The analysis allows to optimize the technique performance by selecting appropriate values for the beam splitter transmission coefficient.
Experiment of thin beam propagation through atmospheric turbulence in the laboratory
Author(s):
A. Consortini
Show Abstract
Thin beam wandering through laboratory generated strong turbulence is experimentally investigated. In the case of small fluctuations and within the limits of geometrical optics, the transverse displacement variance is expected to follow a 3rd-power law dependence on distance. Here we describe the results of measurements made over a few meters path in the cases of strong turbulence.
Ultra-high precision grinding of the glass surface by the surface-charged abrasive tool
Author(s):
Jung Young Son
Show Abstract
On the basis of the microgrinding model the dependencies between the used material properties (fused quartz, pitch matrix, lubricant, abrasive) and controlled parameters of the grinding process (pressure, spindle velocity, etc.) has been obtained. Knowledge of these dependencies is essential for the implementation of the technology for the deterministic fabrication of the precision optical surfaces.
Selective, absorption-interference, anti-laser filters
Author(s):
Z. Mierczyk
Show Abstract
As a result of investigation of construction and technology of anti-laser filters based on coloured glass and interference thin-film coating, the new solutions of absorption-interference filters have been developed. The main goals are: very high and selective absorption, interference filters for several wavelengths (simultaneously) with increased transmission in the visible region and increased energy resistance.
Precision holographic autocollimator: creation, research, priorities
Author(s):
L. I. Konopaltseva
Show Abstract
For the first time the results of investigation in creation a precision (with error of shares of angle seconds) holographic autocollimator (AC), working under natural exploatation conditions (environmental temperature variation from −50°C to +50°C, dynamical loading 19,6 m/s2) are presented. The adventages over analogous ones have been achieved due to use of synthesized hologram optical element (SHOE) in lens, optimizating of lens scheme, its diffragation system.
Laser diagnostics of water plankton
Author(s):
E. A. Chernyavskaya
Show Abstract
On the basis of computer model of energy transfer in photosynthetic unit and locating the excitation energy on the reaction center new laser methods of estimation of chlorophyll concentration in photosynthetic organisms and their pigments have been developed.
Fluorescence diagnostics using photosensitizers in oncological practice
Author(s):
G. N. Vorozhtsov
Show Abstract
The results are described of clinical fluorescence diagnostic observations of tumors, carried out in the course of clinical trials of new photosensitizers PHOTOHEME and PHOTOSENS, developed in Russia for cancer treatment by photodynamic therapy. The construction and performance characteristics of the designed spectrometric and imaging systems have been tested. Methods of tumor diagnostics using fluorescence of these drugs have been developed.
Index distribution in a crystalline lens of the eye
Author(s):
L. H. Liu
Show Abstract
A number of multilayer, gradient index models with distinct ditribution of refractive index within a crystalline lens of the eye have been proposed and analyzed by optical ray tracing method based on several experimental data(1)(2). This paper report the experimental method and results of visualizing the optical pass through the excised crystalline lens using the parallel laser beams which were observed with and without Sheimpflug's principle. It was concluded that this method may be applicable to the living human eye.
Birefringence of the in vivo cornea of the eye
Author(s):
Maung H. Khin
Show Abstract
The birefringence of the in vivo cornea and stress conditions by using birefringent special contact lens which produce a polarization pattern similar to that of the in vivo cornea has been studied by performing theoretical computer simulations. The effect of shape and stress conditions in vivo cornea is also discussed.
The role of spectroscopic characteristics of biological tissues in a laser therapy and diagnostics
Author(s):
V. E. Prokop'ev
Show Abstract
In the paper the results of studies of the absorption and fluorescence spectra of cells and tissues in the (250-1200 nm) are reported. It is shown that irradiation of tissues in the red and near IR regions of spectrum (600-800 mn) is determined by fluorescence of Fe ions equally with the known endogenous fluorophors such as atomic amino acids, reduced NADH, oxidized flavins, and porphyrin compounds. These fluorophors take participation in all basic biochemical and biophysical processes which provide the equilibrium among different gomeostatic systems including immune, hormone, oxidation-reduction ones, etc. Therefore, it is possible to exert a fine control over different gomeostatic mechanisms and to affect the state of the whole organism by the aid of even insignificant external actions imposed on these molecules, for example, by selective photoexcitation of a certain group of fluorophors.
Improving contact lens' fitting evaluation by digital image acquisition and processing
Author(s):
Manuel F. M. Costa
Show Abstract
On this communication we describe a method of automated evaluation of the quality of hard contact lens' fitting on patient's eyes.
Traditionally, in order to check the fitting of a contact lens a fluorescein test is performed, either using a Burton or a slit lamp. The optometrist can get an idea of the fitting's quality simply by looking at the fluorescence at the contact lens' location, evaluating the "smoothness" of the color/brightness distribution. Depending on several factors including the optometrist's skills and experience, the test may take a couple of minutes making it very uncomfortable for the patient.
Our idea consists in automating this inspection process in an inexpensive, easy to implement and user friendly way. We simply propose the substitution of the optometrist's eye by a CCD camera. The camera will be suitably interfaced to a microcomputer. The eye's image can then be digitized and treated. Elementary image processing techniques will be applied. The enhancement of image's contrast and relevant feature's detection is performed. The processed images may simply be directly analyzed by the optometrist in an easier and more efficient way. An automatic diagnostic can also be made available.
Influence of high power XeCI laser on lipid content of atherosclerotic plaque
Author(s):
S. V. Mel'chenko
Show Abstract
Lipid content of extracts based on atherosclerotic plaque layers irradiated by XeCl laser was compared with that prepared from atherosclerotic tissue before irradiation. In addition, spectra of cholesterol solutions were recorded before and after influence of laser beam. Up to 20% of laser energy was discovered to be exhausted for dissociation of lipid molecules.
Advances in 3D microscopy by optical scanning holography
Author(s):
Kyu Doh
Show Abstract
Optical scanning holography (OSH) is a technique in which 3-D information of an object can be recorded by 2-D scanning [see reference]. The technique involves optical scanning the 3-D object by a so-called time-dependent Fresnel zone plate (TDFZP). The TDFZP is created by the superposition of a plane wave and a spherical wave of different temporal frequencies. When the object is optically scanned, a photodetector collects the scattered light and delivers a heterodyne current as output. The current is then mixed down to become a demodulated signal. When the demodulated signal is synchronized with the x and y scans of the x-y optical scanning system and fed to a 2-D display, what is displayed in 2-D is a hologram or a Fresnel zone plate coded information of the object being scanned. To decode the information optically in real time, the holographic inforthation could be transferred to a spatial light modulator (SLM) for coherent reconstruction. Digital reconstruction is also possible by convolving the hologram with a free-space impulse response. Whereas the work of optical scanning holography has been concentrated on on-axis techniques which inherently produce twin-image upon reconstruction (or decoding), in this paper we introduce a novel technique in which the twin-image can be eliminated in the context of optical scanning holography.
Optical modelling of human eye including the photoreceptors: determination of the absorbed power in the photoreceptors
Author(s):
S. Geronimi
Show Abstract
Many experiments in physiological optics, optical design, digital image processing, robotics must take into account the behaviour and the contribution of the optical system of the eye (cornea, crystallin lens) as part of the whole system. But, if we need some informations about visual functions, we must take the role of the retina (representing the detector of the eye system) into account. The mosaic formed by retinal photoreceptors initiates the visual process by converting the continuous image transmitted by ocular optics to a discrete array of signals. Thus, the photoreceptor mosaic provides all spatial informations to higher stages of visual process. The photoreceptors have two functions : to conduct light to the pigments (optical function) and then to convert light energy into a neural response (photochemical function). Therefore we have been developping a computer model of the human eye including the spatial structure of the photoreceptors in the retina in order to study their role in the visual system. Our model predict the light illuminance of a spatially modulated visual stimuli on the retina and the absorbed flux in the photoreceptors.
Detectability of absorbing inhomogeneities within a highly diffusing slab
Author(s):
Giovanni Zaccanti
Show Abstract
The possibility to obtain imaging of biological tissues by using visible or NIR radiation is widely investigated. One of the most studied problems is breast imaging, since it is desirable to have a non invasive method, alternative to x-ray mammography, to be used for early detection of tumors. Biological tissues are highly scattering media and photon migration occurs with many scattering events. Therefore trajectories of photons can vary greatly from straight lines causing a decrease in contrast and in spatial resolution. Some methods to improve imaging have been developed based on measurements both in the time domain and in the frequency domain1-5. The purpose of this work was to determine, by means of numerical simulations, the effect of a discrete inhomogeneity on photons migrating through an otherwise homogeneous slab of diffusers. The slab was assumed as a simple model for a breast compressed between two plane parallel plates. The presence of a tumor was simulated with an absorbing sphere. The image of the inhomogeneity was obtained moving a coaxial source-receiver system with respect to the inhomogeneity and plotting some parameters related to the received signal.
Detection of immunological reaction with the attenuated total reflection (ATR) technique
Author(s):
Ericka Rodriguez
Show Abstract
The sensitivity of the Attenuated Total Reflection (ATR) technique to surface modifications allows the study of biological or medical phenomena where solutions seggregate to form a layer on the walls of the sample holder. An aluminum thin-film is deposited at the bottom of the container where the reaction takes place and is attached to a prism. During the reaction a layer is adsorbed on the aluminum film. The study of the total reflectivity in this system when the incoming light enters through the prism shows a resonant absorption peak that shifts towards larger angles of incidence when monochromatic light is used. This shift is related to the optical properties and the thickness of the adsorbed layers and may be quantified. We present here the study of Antigen-Antibody reactions with the aid of this technique.
Optical fiber monitoring in laser microsurgery
Author(s):
A. N. Zmievskoy
Show Abstract
The express-diagnostics system acquires a main significance to be a success in making minimal invasive laser operations within hardly achieved regions of a human organism as the only means permitting to supply both safety and optimal treatment efficiency.
Optical deformation and temperature measurement of windage heating effects on high speed rotating discs
Author(s):
Richard W. T. Preater
Show Abstract
Pulsed Laser Electronic Speckle Pattern Interferometry (ESPI) is close to a real-time experimental method of analysis of component deformation. In-plane displacement and strain information may be obtained over a wide range of rotational speeds. Liquid crystal material sprayed on to the component surface gives a clear transitional colour change at specific temperatures for windage heating effects at high speed and may be suitable for temperature distribution measurements.
Development of an opto-chemical gas sensor using fine metallic-oxide film
Author(s):
Kazutoshi Noda
Show Abstract
A p-type semiconducting metallic-oxide film is provided in a CO gas atmosphere, and the light is irradiated onto the film, in this system, the light transmission factor depends on the gas concentration. Utilizing this principle, the optical response of this system to CO gas was studied. As the result, it was found that NiCo2O4 gave the maximum light transmission intensity change.
Optical 3D measurement of objects with technical surfaces
Author(s):
J. Gerber
Show Abstract
The digitalization of CAD-models, the complete manufacturing control and the timely quality control of components are important tasks of modern industrial inspection. In many cases the 3D-object shape as well as its deviation from a certain master object is of special interest, whereas optical measuring techniques based on structured light find increasing application /1 - 4/. Unfortunately, as a rule the application of these optical 3D-inspection systems leads to difficulties if the surfaces under test are strongly structured yielding to a shadowing within the image field. Moreover, distortions appear if the detector records too high light intensities in some ranges of the image caused by light reflection and diffraction at the surface of the object. So, within these ranges of the image one could not get useful values of measurement of the coordinates. The method of structured illumination allows the development of a concept of measurement which can avoid these illumination-caused difficulties.
A laseroptical strain sensor for non contact and whole field strain analysis
Author(s):
T. Walz
Show Abstract
A new laseroptical strain sensor is presented for application in material testing. The sensor uses the principle of speckle interferometry with dual illumination technique for measurement of the in-plane component of the deformation of samples under load. Computer evaluation of the resulting correlation fringes give quantitative data about the deformation and strain distribution on the whole surface of the sample. Therefore this technique enables the measurement even at inhomogenuous structures and components and will show local effects like yielding, creeping, shear bands, defects, and many more. Principle and practical application examples will be given in this paper.
Measurement of velocity of random flow with spatial temporal image
Author(s):
Hiroyuki Inaba
Show Abstract
A new method for measuring a velocity distribution perpendicular to the direction of the random flow such as debris flow is proposed. Our method is based on a spatial temporal image of the random flow and use a modified version of Hough transformation. We confirm the performance of our method by a computer simulation.
Coherent, infrared, heterodyne detection systems
Author(s):
M. Strzelec
Show Abstract
The paper presents the new experimental data on coherent, infrared detection systems utilizing low power, CO2 laser transmitters, pulse compression technique and several cooled and room-temperature, HgCdTe (MCT) photodetectors of infrared radiation. Results include the noise characteristics, sensitivity and noise equivalent power (NEP) for heterodyne detection.
Stitching interferometry: principles and algorithms
Author(s):
Y. J. Fan
Show Abstract
With modern commercial interferometers, high precision measurement can be made of flats and spheres.1,3 However, the interferometric measurement of aspheric surfaces may be very hard to perform. The problem is that, if the aspheric surface has a large departure of slope from the best fitting reference surface, an interferogram acquired without some sort of aspheric null elements contains too many fringes to be detected.2,3 In other words, such an interferogram is unsolvable.
Lateral shearing interferometry with high accuracy
Author(s):
G. W. R. Leibbrandt
Show Abstract
A phase-stepped lateral shearing interferometer is presented with the same accuracy as conventional interferometers. This is achieved among others by shearing over a substantial fraction of the wavefront diameter.
Characteristic measurement of surface acoustic wave using a heterodyne interferometer
Author(s):
Suezou Nakadate
Show Abstract
A new method for measuring a wavelength and standing wave ratio of a surface acoustic wave(SAW) is presented, which is based on a heterodyne interferometer using first-order diffracted light beams from a SAW device and a grating. Phase and amplitude distributions of a beat signal from the interferometer by moving the substrate or the grating give such characteristics of the SAW. Experimental verifications are presented in two cases of the movements of the object and grating. Two-dimensional measurements around an interdigital transducer of a SAW device are also given.
New method of multimode fiber interferometers signal processing
Author(s):
Yuri N. Kulchin
Show Abstract
New method of multimode fiber interferometers signal processing is suggested. For scheme of single fiber multimode interferometers with two exited modes the method based on using of special fiber unit is developed. This unit provides the modes interaction and further sum optical field filtering. As a result the amplitude of output signal is modulated by external influence on interferometer. The stabilization of interferometer sensitivity is achieved by using of additional special modulation of output signal. The achieved parameters for double mode scheme: temporary stability - 0.6% per hour, sensitivity to interferometer length deviations - 3.2 nm.
The role of topological phases in the microinterferogram formation
Author(s):
A. V. Tavrov
Show Abstract
Novel measuring and interpretation concept, that considers separately dynamical and topological phases, has been elaborated. Preliminary experiments have shown the confirmation of the role of topological phases in the interferogram, obtained with a polarized light. The concept was applied to the real time surface monitoring.
Absolute distance measurement
Author(s):
R. Dändliker
Show Abstract
Multiple-wavelength interferometry offers a great flexibility in working distance and sensitivity by an appropriate choice of the different wavelengths and it can be operated on rough surfaces. A novel concept of a multiple-wavelength source, using laser diodes, has been developed. It allows to get an absolute calibration of the synthetic wavelengths by electronic beat-frequency measurements. Experimental results show that a calibration of the synthetic wavelength in the millimeter range with an accuracy better than 10-5 is feasible. A three-wavelength heterodyne interferometer is described and results with 9 μm accuracy on a range of 200 mm are presented. Moreover, a lock-in CCD image sensor has been developed and implemented in our system for applications with non-cooperative targets.
High intensity, single mode He-Ne laser as a light source of multi-dimension interferometer
Author(s):
Shuko Yokoyama
Show Abstract
Highest intensity, single mode He-Ne laser can be obtained by combination of 3-modes operation of a 3∼4 modes oscillating laser tube and a polarizer for selection of a single mode. In this experiment, as a 3∼4 modes oscillating laser tube, a tube whose cavity length is 35cm and output intensity is 5mW was employed. By selectively using the center mode of 3-modes oscillation as a single mode, highest intensity, single mode He-Ne laser has been realized.
For a particular mode stabilization, the polarization stabilization method whose control signal is intensity is usually used. However, mode stabilization at the gain curve center is difficult in this method. Moreover, detection of the intensity is uncertain due to temperature drifts in the detector sensitivity and amplifiers, and contamination in the cavity mirror and detector surface, resulting in decreasing the frequency stability.
In this experiment, intermode beat frequency change by Frequency Pulling which is strongly related to the mode position was utilized for the stabilization. The difference frequency of two intermode beats generated by the center mode and two other modes which oscillate at each side of the center mode is used as a control signal. It is convenient for the stabilization that the position of this frequency variation corresponding to the most intense center mode oscillation is at middle of its slope. Because the control signal based upon the frequency can be processed digitally, this stabilization method is free from uncertainties which is inevitable in the polarization stabilization method.
Fiber-optic vibration and acoustic sensor systems for traffic monitoring
Author(s):
N. Fürstenau
Show Abstract
This paper describes fiber-optic microinterferometer vibration and acoustic sensor systems developed for optical monitoring of traffic related parameters over large distances. The sensors are characterized under laboratory conditions and results of initial field tests in an Experimental Surface Movement Guidance and Control System (ESMGCS) for airport ground traffic surveillance are presented.
Embedded intrinsic Fabry-Perot optical fiber sensors in the cement concrete structure
Author(s):
Ki-Soo Kim
Show Abstract
Civil structures play important roles in human being's life for convenience and practical purposes. But in the same manner, it needs proper maintenance because of the change of nature such as earthquake, typhoon, flood and the degradation of themselves with passing of time. Therefore, it has emphasized necessity of health monitoring system that always measures degree of deterioration of civil structure and predicts the life span of the structure and informs its repair time. Besides the existing strain gauge, potential candidates of the sensing elements of the system are optical fiber sensors because of no disturbance from electromagnetic waves, good durability, quick response. In this experiment, embedded intrinsic Fabry-Peort optical fiber sensors were employed.
A study on the dynamic scheme of optical gyrocompass
Author(s):
Seok-Jeong Lee
Show Abstract
A dynamic scheme of the optical fiber gyrocompass for ships was proposed adopting the curve-fitting method of the static scheme. The advantage of a dynamic scheme is insensitivity to the drift effect. The accuracy of this system was 0.6°.
Feedback-insensitive operation of open-loop fiber-optic gyroscope with erbium-doped fiber amplifier source
Author(s):
Hee Gap Park
Show Abstract
Broadband erbium-doped fiber sources have emerged as promising sources for navigation-grade fiber-optic gyroscope owing to their excellent thermal stability of the spectrum as well as the high power output[1]. Various source configurations have been investigated for the higher output power and the broader bandwidth with more stable mean wavelength[2]. Among them, fiber amplifier source (FAS) configuration[3] is worthy of note. In this configuration, the doped fiber acts not only as a source but also as an amplifier of the returning gyro signal, resulting in two or three orders improvement in the detected power. However, this configuration also has an apparent disadvantage that the source characteristics (especially spectrum) are very sensitive to the feedback from the gyro as the source cannot be isolated, which may lead to the scale factor instability. In this respect, the FAS configuration has been thought more adequate for the closed-loop gyro rather than for the open-loop gyro. In this paper, a feedback-insensitive operation condition of open-loop fiber-optic gyro employing erbium-doped FAS was investigated to stabilize the scale factor despite the existence of feedback.
Fiber optic acoustic sensor-PZT modulation
Author(s):
Hikaru Takahara
Show Abstract
The fiber-optic acoustic sensing have been studied 1)-5) by utilizing the pressure-phase shift in laser light going through an optical fiber. We studied 5) previously an ultrasonic sensor using a polarization-maintaining optical fiber (PMF). In this paper, the relation between the pressure-induced phase shift and the laser light transmitted through a PMF is more concisely analyzed. Moreover, the broad range of the linear relation by the phase modulation using a Piezo-Electric Transducer (PZT) is studied.
Fluorescent decay time optical sensor for temperature measurement
Author(s):
Y. W. Lin
Show Abstract
On-line temperature measurement of rotors of electric machines and other high voltage electric equipments is great value for safety operation, but the existing of high voltage, strong electric-magnetic field and small installation space make it difficult to achieve this measurement, especially in the case of rotary or motional status.
In this paper, a method for this kind of measurement by calculating the decay time of the fluorescence is presented. It uses a phorsphor powder material, which is sticked on the surface of the rotor (or other tested surfaces) by mixing some resin and activated by a ultra-violet light pulse, which is delivered onto the surface through an optical fiber. As the pulse is over, the fluorescence emitted from the powder is collected by another fiber and sent back to a sensor with it' s associated circuit.
A new electrooptical device for detecting magnetic fields
Author(s):
P. Mormile
Show Abstract
The light beam propagation at a prisms-liquid crystal interface is studied both theoretically and experimentally making a comparison between a theoretical model based on the Berreman formalism and the experimental results. Our results suggest the possibility of employing such interface as a new electooptical device for detecting magnetic fields.
The application of dual-wavelength 3.39 um HeNe laser on absolute distance interferometry
Author(s):
Ren Weiming
Show Abstract
A dual-wavelength 3.39μm HeNe laser is used to construct a beat interferometer which can realize the measurements of absolute distances in this paper. With this laser the interferometer produces a series of spatial beat wave. By directly measuring the fractional orders of these beat waves, the accurate value of measured length can be calculated in terms of them. The experiments have shown that the measurement accuracy of fractional order is 32μm.
Topological phase and interpretation of the interferometer data
Author(s):
V. A. Andreev
Show Abstract
There have been many recent manifestations. of topological phases in optics, but in the all works, both theoretical and experimental, these phases are considered only as some interesting natural phenomena. We will show that topological phases can be used for constructing the devices capable of measurement both geometrical and optical characteristics of a surface, that is combining the properties of profilometer and ellipsometer.
Novel heterodyne interferometer for measuring displacement
Author(s):
Yong-jun Wu
Show Abstract
A novel heterodyne interferometer with a laser diode for measuring displacement is proposed. The heterodyne carrier signal is created by using an acousto-optic modulator. The back surface of a λ/4 plate serves as the reference mirror. These make the interferometer have very simple construction. The displacement is obtained by measuring the phase difference between the measurement signal and reference signal.
Fringe design in automated fiber-optic grating interferometer
Author(s):
Anna Kozłowska
Show Abstract
The technology progress in mechanics, material science and manufacturing which has been observed over the past decades, has created a great demand for reliable, fast and fully automated inspection methods. Among the optical methods, a very useful tool for in-plane displacement measurement is the grating interferometry [1]. The features of this method are: high sensitivity, versatility and high accuracy of in-plane displacement determination. In order to meet requirements concerning the miniaturisation of the measurement system, the new fibre optic version of the grating interferometer [2] has been proposed. This realisation enables measurement in difficult to access locations which significantly increased the versatility of the system. The novelty of the system is utilisation of laser diode as a light source. Using the spectral properties of the laser diode, especially the possibility of controlled wavelength varying allowed to create a smart fringe design system, which is used for automatic interferogram analysis.
Measurement of the double layer-capacitance of aluminium samples by holographic interferometry
Author(s):
K. Habib
Show Abstract
In the present investigation, holographic interferometry was utilized for the first time to measure the double layer-capacitance of aluminium samples during the initial stage of anodization processes in aqueous solution without any physical contact. The anodization process (oxidation) of the aluminium samples was carried out chemically in different acid concentrations (0.5-3.125 % H2SO4) at room temperature. In the mean time, a method of holographic interferometric was used to measure the thickness of anodization (oxide film) of the aluminium samples in aqueous solutions. A long with the holographic measurement, a mathematical model was derived in order to correlate the duoble layer-capacitance of the aluminium samples in solutions to the thickness of the oxide film of the aluminium samples which forms due to the chemical oxidation. The thickness of the oxide film of the aluminium samples was measured by the real time-holographic interferometry . Consequently, holographic interferometric is found very useful) for surface finish industries especially for monitoring the early stage of anodization processes of metals , in which the thickness of the anodized film can be measured as well as the duoble layer-capacitance of the aluminium samples can be determined during the anodization processes.
Photothermal displacement in an interference fringe
Author(s):
K. Hane
Show Abstract
The photothermal displacement of the selfstanding film in an interference fringe is investigated theoretically and experimentally. It is found that the bistability of the displacement and the selfexcited vibration of the film are generated when the film is placed in the standing wave produced by the continuous wave laser light reflected from a mirror. In the selfexcited vibration, some nonlinear effects such as light intensity threshold for excitation, vibrational amplitude saturation etc., are obtained from the theoretical consideration. The theoretical results explain well the experimental results. The obtained results are useful for the optical activation of the resonator sensor and mechanoptical bistable switch.
Modulated pitch phase gratings used in displacement encoder
Author(s):
K. Hane
Show Abstract
The binary phase grating with the modulated pitch is investigated for a simple displacement encoder. The index grating consists of a binary phase grating to eliminate the zero-th order diffraction and the pitch of the grating is modulated to compensate the higher harmonics of the encoder displacement signal. Therefore, an undistorted sinusoidal signal as a function of displacement is obtained by simply superimposing a conventional binary amplitude scale grating on the modulated pitch phase gratings with any air gap between the gratings. The characteristics of the proposed gratings and the encoder signal are investigated by the Fresnel diffraction theory. The proposed grating was fabricated lithographically and the signal was examined experimentally. Considering these results, this method can reduce interpolation error and will be effective for an encoder in precision machining.
Fiber optics displacement sensor based on clad modes detection
Author(s):
A. Andriesh
Show Abstract
A modified configuration of fiber optic displacement sensor, based on detection of clad modes is described. For clad modes detection the end segment of the fiber is bent and placed in an integrating sphere. Experimental set-up and transmission characteristics are presented.
Ring laser gyros with control of backscatting waves interference
Author(s):
K. V. Astakhov
Show Abstract
Errors of a miniature Zeeman ZLK-16 RLG, caused by the coupling of countrary waves, are considered. A models of such a coupling effects, based on the radiation backscattering at the resonator mirrors, shows the way to minimize lock-in and accompanying errors without high upgrade of RLG mirrors technology. Resonator geometry parameters, that make effect on the coupling level, are presented, and thus provide a means for coupling minimization by the control of ring cavity geometry. The application of such method for ZLK-16 RLG design, referred at the article, shows that such method of coupling minimization is significant to decrease irreproducible components of laser gyro errors, especially turn-to-turn repeatability and scale factor stability.
Laser system for alignment and testing of high quality optical cavities and mirrors
Author(s):
V. V. Azarova
Show Abstract
It is described the method and the laser system for measure of high quality optical cavity characteristics based on the multibeam Interferometric effects. The discussion of the opportunity to make coefficients of total and diffraction cavity loss measurements, reflectivity measurements of low-loss highly reflecting mirror coatings and gain measurements of the active substance is given. The possibility to control of the resonance cavity spectrum, a level of selection, a quality of the mirrors alignment and an accuracy of the cavity monoblock making is discussed. It is shown that measurement method and system are suitable for measure R before 0.9999 and has own primary range of application.
Multichannel spectral imaging system consisting of dichroic mirrors
Author(s):
Akiko Hirai
Show Abstract
A multichannel spectral imaging system consisting of dichroic mirrors is proposed and evaluated. The system is expected to have the highest signal-to-noise ratio because of the largest optical throughput. The signal-to-noise ratio is studied and compared with that of another fast spectral imaging technique.
A new type of IFOG with depolarizers
Author(s):
Fengping Yan
Show Abstract
In this paper, a new type depolarized fiber optic gyroscope is described. Sensing coil is constructed by single-mode optical fiber. A superluminescent diode source is used to reduce both the coherent scattering effect and Kerr effect. Two depolarizers with 1.0% degree of polarization were used to reduce the output bias drift and improve the scale factor. Long-term bais stability better than 2.0° /hr is obtained during ten hours observed time.
Fiber-optic AC voltage sensor
Author(s):
Bong Kyu Kim
Show Abstract
A fiber-optic voltage sensor is demonstrated with a new signal processing scheme that displays the magnitude and the waveform of applied signal using fringe counting method. The detrimental polarization modulation effect of the sensor was overcome by using a fiber-optic half-wave plate.
Investigation of Kerr effect in FOG
Author(s):
Fengping Yan
Show Abstract
The Kerr -induced rotation-rate error in fiber-optic gyroscopes was described theoretically, and an effective method was proposed to reduce this rotation-rate error.
Observation system of pyroclastic flow with digital video-image processing
Author(s):
Yasumasa Itakura
Show Abstract
A new observation system of pyroclastic flow is based on spatio-temporal derivative method for occurrence-detection and spatial filtering method for velocity measurement by digital image processing of thermal infrared video images of the flow. Our system has been successful in observing the pyroclastic flow occurred at Mt. Unzen-Fugen.
Measurement of thermal expansion by statistical interferometry
Author(s):
H. Kadono
Show Abstract
Generally, in conventional optical interferometry, generation of speckles has been regarded as a noise and an error source degrading the reliability of the measurement because the phase is determined in a completely deterministic way. Recently, we have proposed and developed a new interferometric technique called statistical interferometry and demonstrated its validity1,2). In the method, completely random wave fronts, i.e. speckle fields, play a role of the standard of phase in a statistical sense. In the present study, we have applied the statistical interferometry to the measurement of thermal expansion of an object.
Birefringence induced by external forces in optical fibers
Author(s):
Diana Tentori
Show Abstract
Refractive index changes induced by twisting, bending, and compressing samples of multimode fibers were investigated using holographic interferometry and conoscopic examination in a polarimeter. Observations have been made utilizing a non-expanded laser beam traveling through short samples of silica and plastic fibers.
Optical sensing with photorefractive double phase conjugate mirror
Author(s):
Alexei A. Kamshilin
Show Abstract
We have demonstrated a simple optical sensing scheme based on a Double Phase Conjugate Mirror (DPCM) recorded in a Bi12TiO20 waveguide-like sample. In the proposed scheme the DPCM acts as a converter of the optical fiber mode fields and allows zero-order interference detection of the mode phase and amplitude modulation. This scheme can be useful for multimode fiber-optic sensor applications.
Optical fiber sensor based on optical feedback effect of a laser diode
Author(s):
Seiichi Kakuma
Show Abstract
In this work we report the results of the experimental investigation on the optical fiber sensor (OFS) applying the optical feedback effect of laser diode. An optical path length change of a sensing fiber is precisely determined via the light frequency shift of a LD whose frequency is locked to the path length of the fiber. Another LD is used as a local oscillator to determine the frequency shift. The light frequency is accurately determined from a beat signal observed in the mixture of lights from. both LDs.
Numerical study of the Gaussian beam effect in the phase doppler method
Author(s):
Yoshihisa Aizu
Show Abstract
Phase Doppler anemometry (PDA) suffers from the Gaussian beam effect which causes erroneous particle sizing. This paper studies numerically the Gaussian beam effect by using the computer simulation which is based on the generalized Lorenz-Mie theory (GLMT). Numerical results should be carefully considered in design of the PDA optical configuration.
In-process measurement of concave mirror by fiber grating line-Hartmann test
Author(s):
Tsuguo Kohno
Show Abstract
A new Hartmann test method is developed using a single optical fiber grating and a rotating spindle instead of using clossed fiber grating sheets. Being illuminated with laser light, the fiber grating generates one-plane fan-like diverging multiple rays of almost same intensities. Reflected rays from the mirror surface under test are converging to make straight multi-spot pattern. A CCD camera detects the pattern and a personal computer analyzes it into sectional figure error. For the workpiece on a rotating spindle, several measurements are carried out synchronously to the deferent turning angles, and these sectional figures are synthesized into a three dimensional figure error map. Experiments of on-machine measurement showed it as a stable measurement method of about 1/10λ accuracy and confirmed to be applicable to in-process measurement for machining control.
The choice of the photo-senitive detection systems for use in triangulation based optical microtopographers
Author(s):
Manuel F. M. Costa
Show Abstract
Non invasive topographic characterization of rough surfaces is of major interest in the industrial world.
For some years we are dealing with the development of inspection's systems able to cope in a simple accurate and reliable way with the specific requirements herein involved. Our systems are based on a discreet triangulation procedure where the topographic information is obtained from the horizontal shift incurred by the bright spot created, by an oblique collimated light beam, on a surface when it is displaced vertically. A laser beam is focused onto a small, diffraction limited, spot on the surface and is made to scan it over the desired region. The sample is placed on XY high accuracy step motion table to perform the scanning of the sample' areas of interest. The bright spot is perpendicularly imaged onto a
photo-sensitive detection system and its position obtained. The corresponding horizontal spot's shift on the reference plane is then computed. At each sampled point the distance between the surface and a reference plane is then easily calculated allowing the calculation of statistical surface characterization parameters and the tridimensional reproduction of surface's relief.
The decision about the right
photo-sensitive detection system is our major concern in this communication. Special attention is paid to the use of CCD's linescan cameras and of the so called PSD's identifying the specific inspection situations where each one represents the best choice.
Use of standard deviation measurements for the contrast enhancement of speckle addition fringe patterns
Author(s):
Fernando Mendoza Santoyo
Show Abstract
The electronic speckle pattern interferometer in the double pulse addition mode can be used to measure physical parameters in unstable environmental conditions. However, due to additive speckle noise the fringe patterns obtained have poor contrast. Some methods that use subtraction of addition double-pulsed fringe patterns improve fringe visibility but impose a limitation in measurement time ranges. In order to increase this range, to be limited only by the pulse separation, the contrast enhancement of double-pulsed addition fringe patterns using a spatial filter based on local standard deviation measurements is investigated. Computer simulations and experimental results are presented.
Photothermal measurement using a laser speckle strain gauge
Author(s):
Ichirou Yamaguchi
Show Abstract
Photothermal strain of plastic plates caused by laser beam irradiation has been detected by a laser speckle strain gauge. This noncontact method enables both the initial bending and the uniform dilation to be analyzed. A theoretical calculation showed a good agreement with the experimental results.
Fiber optic rate gyroscopes
Author(s):
Joung C. Ha
Show Abstract
The USAF Avionics Laboratory is developing miniaturized fiber optic gyroscopes as replacements for new or existing mechanical devices which have become expensive, unreliable and difficult to obtain. The modular architecture of the fiber optic rate gyro (FORG) utilizes a basic single axis DC In/DC Out instrument and associated electronics packaged within a cylinder approximately 1 inch in diameter and 2.625 inches in length. Application to an individual system requires only a small interface adapter to accommodate unique parameters. The basic instrument and interface adapter can often be packaged together into a form, fit, and function replacement for the original device.
Application of a two-dimensional direction dependent sub-um-offset sensor
Author(s):
R. Güther
Show Abstract
The principle of a two-dimensional direction dependent offset-sensor is shown in figure 1. The radiation of an 820 nm-laser diode working in the superluminescent range is launched into fibre 1 with monomodal propagation. The light of the monomode fibre excites any combination of 5 modes of a few mode elliptical fibre via a butt end coupling. If the fibre 1 is translated in transverse direction by ξ and η then the combination of the excited modes in fibre 2 changes.
Large field of view surface microstructure measurements
Author(s):
James C. Wyant
Show Abstract
This paper describes a computerized interferometric microscope system for the measurement of surface microstructure in which high spatial resolution, small field of view (FOV), measurements of surface microstructure are stitched together to give highly accurate large FOV maps of surface microstructure. A FOV of several millimeters having micron spatial resolution and nanometer or better height resolution can be obtained.
Phase compensation in phase shifting interferometry
Author(s):
Katsuyuki Okada
Show Abstract
Phase shifting technique is widely used in interferometry, but one drawback of the technique is necessity of exact phase shift value, and the error of the phase value causes severe error in phase calculation.
We have reported a method to obtain the exact value of the phase shift and the phase distribution of the wavefront from phase shifted interferograms without additional information
1,2). In the technique, the amount of the phase shift is estimated from all the interferograms with different amount of phase shift by a nonlinear least square estimation. To obtain the phases, an iterative calculation is used because of large number of unknowns of the equations. In this paper, the convergence of the estimation is examined as a function of the number of interferograms used for measurement and of the amount of total phase shift.
Three-dimensional multi-layered optical card storage
Author(s):
Takuo Tanaka
Show Abstract
Optical card storage is one of the most compact form of data storage, which stores information on plastic card of credit-card size. This method of optical storage has been intensively explored for commercial applications. However, the capacity of this storage is strictly limited. The capacity is given by the total size of memory area divided by the extent of laser-beam spot, and the minimum size of spot is as large as a half of light wavelength due to the light-wave diffraction. To overcome this limitation, we record pits into multiple layers in a volume medium in three-dimensions rather than only in the surface of the medium[1-2]. In this paper, we describe the multi-layered optical card system, which we developed.
A new type of optical microphone
Author(s):
Yongchen Xu
Show Abstract
The invention of scanning near-field optical microsopy(SNOM)[1-2] has opened a new era of optical resolution beyond the diffraction limit of conventional optical instruments. The SNOM is using a near-field optical probe to confine the lateral space of the optical field within a subwavelength scale. The probe is made of glasses, quartz or metals, being formed into a tip[2]. The light from a big entrance travels to the small end of the tip, total internal reflection inside the wall of the tip, makes almost the whole entered energy pass through the small tip end. In this case at the small tip end the energy density increases greatly. This we call a focussing effect. Microphones[3] are commonly using a membrane that vibrates with audiowave frequency in the air next to it. The present design is based on a tip divided into two parts. One side of the tip is a membrane, the other side together with the entrance of the tip are fixed. The end area will vary with the vibration of the membrane. Therefore the signal of the light detector provides a measure of the vibration.
Recovering of surface spectral reflectance from the output signal of image sensor device
Author(s):
Seung Ok Park
Show Abstract
Object color is defined by the surface spectral reflectance. However, the output signal of an image sensor device is affected by the other physical factors. The output signal for the same object color is different according to the device characteristics. The spectral sensitivity of an image sensor device is the most important factor. To recover the original color from the output signal, two kinds of studies are performed. One is to develope a spectral sensitivity measurement system and the other is to obtain color characteristic vectors which can represent a wide variety of any spectral reflectance accurately.
Capillary optical fiber evanescent wave refractometer sensor
Author(s):
Juraj Doupovec
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The new principle of the refractometer sensing based on capillary optical fiber is pre- sented. The evanescent wave penetration into the cavity of this fiber is evaluated and the first experimental results are shown.
Determination of strain from holographic interferometric fringe analysis
Author(s):
Seung Ok Park
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Strains under three dimensional deformation are determined from holographic interferometric fringe. For a cantilever beam subjected to the combined forces of out-of plane and in-plane deflection, holographic interferometric fringes are obtained experimentally. From a fringe pattern, the effect of the out-of plane deflection and the in-plane deflection are analysed, respectively. The 3rd order polynomial of displacement distribution is obtained using regression method. Therefore strain can be determined from the second derivative of the polynomial. The experimental result is compared with the numerical analysis by finite element method.
Status of Pohang light source
Author(s):
Won Namkung
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The Pohang Accelerator Laboratory (PAL) has completed a 2-GeV synchrotron radiation source named Pohang Light Source (PLS) by the end of 1994 [1]. The PLS consists of a 2-GeV electron linear accelerator and a 2-GeV storage ring. The PLS is the first synchrotron radiation facility ever built in Korea. The critical photon energy is 2.8 keV at 2-GeV operation. Thus, the PLS is expected to serve many users in vacuum-ultraviolet (VUV) and x-ray regions of the photon spectrum for various research such as basic science, applied science, and industrial and medical applications. Currently, there are two beamlines; one for VUV application and one for x-ray application. This number will be increased to six within a short period of time.
High average power KrF laser-plasma x-ray source for lithography at 1nm wavelength
Author(s):
I. C. E. Turcu
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A laser-plasma X-ray source has been developed at the Rutherford Appleton Laboratory for application to x-ray lithography at 0.18μm and beyond, as well as for generation of deep structures. This source provides a calibrated X-ray output of up to 1W (average power) 1nm wavelength (Cu L-shell emission) and 1.5W @ 1.4nm (Fe L-shell)1. Fig. 1 shows a schematic of the RAL laser-plasma x-ray source.
Investigations of x-ray emission from a laser-irradiated gas puff target
Author(s):
Henryk Fiedorowicz
Show Abstract
A plasma produced by high power laser irradiation of a solid target emits strong X-ray radiation in low photon-energy range (soft X-rays and MN radiation) and is considered to be used in many applications such as X-ray optics, material science, microlithography, and biology1-5. A great disadvantage of the laser plasma X-ray sources is the production of target debris by the laser plasma, that may damage optics and X-ray exposed specimens placed in the interaction chamber. To avoid the debris production we have proposed to irradiate, instead of a solid target, a gas puff target, formed by pulsed injection of a small amount of gas into a laser focus region6-8. Our further studies concentrated on optimization of X-ray production from laser-irradiated xenon gas puff targets in 1-keV photon-energy range for X-ray lithography applications9,10.
Research on compact, bright, coherent x-ray sources at RAL
Author(s):
J. Zhang
Show Abstract
New possibilities for compact, bright, coherent x-ray generation have recently emerged through rapid advances in short pulse, multi-terrawatt (TW) laser technology. We present here our recent developments and progress on high gain recombination x-ray lasers and efficient x-ray harmonics generation from solid surfaces using a 2 ps, 20 J chirped pulse amplification (CPA) beam from the VULCAN Nd-glass laser facility (λ=1.053 μm) at Rutherford Appleton Laboratory (RAL).
Recent progress on soft-x-ray lasers research in SIOFM
Author(s):
Zhizhan Xu
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Recent progress on the development of soft-x-ray lasers at SIOFM are presented, including a line coincidence experiment for photo-resonant soft-x-ray lasers, an experiment on a multi-groove target for enhancing the gain coefficient of recombination lasing by Lithium-like ions and a quantitative study on the evolution of nonuniformity of plasma column served as X-ray laser medium.
Radiative cooling instability in recombination x-ray laser gain medium
Author(s):
Ling-qing Zhang
Show Abstract
X-ray emission nonuniformity has been observed in recombination X-ray laser gain media. Time-resolved results show that the nonuniformity enhances when the laser heating stops. This phenomenon can be reasonably explained by an instability associated with the density dependence of radiative cooling losses. Discussion of the influence of the nonuniformity on the gain make-up for recombination X-ray lasers has been presented.
Pulsed-waveguide-modes of x-ray capillary lasers
Author(s):
S. V. Kukhlevsky
Show Abstract
We present an analysis of the pulsed waveguide modes (recently introduced in [1, 2]) and their propagation constants for an X-ray capillary laser. The optical losses of the pulse-waveguide modes are calculated for the SiO2 - capillary laser operating in the spectral region λ = 0.62 - 12.4 nm. We shows that the guiding effect plays the important role in. the laser-beam formation. By employing the pulsed-mode approach, we calculate the angle intensity-distribution of the output radiation.
Gain calculation of He-like Mg soft x-ray laser
Author(s):
Dalwoo Kim
Show Abstract
In this paper, we have studied the He-like soft x-ray laser in a magnesium microtube target pumped by a short laser pulse. This target configuration could simplify the irradiating system, reduce the pumping power and improve the efficiency of energy absorption. In addition, this target configuration could converge the plasma, therefore the electron density will keep high after the plasma expansion, which is favorable to high gain. We chose He-like sequence ion other than the usual H-, Li-, or Na-like ones as the medium based on the reason that the unique shell structure of He-like ion is favorable to both three body recombination and electron collision pumping. At early time, population inversions take place when H-like ions become He-like ones through three body recombination when the plasma rapidly expands and cools. Later on, as lasing occurs, population inversions are consumed, but they can be replenished by the contribution of electron collision pumping due to the full shell structure of He-like ion, which is similar to that in Ne-like circumstance, therefore high gain is expected. In addition to the confirmation by a simple analytical hydrodynamic model[1], Charatis et al.'s experimental results[2] also support our conjecture.
Simulating experiment and numerical reconstruction for x-ray hologram
Author(s):
Xuming Zhang
Show Abstract
For studying X-Ray holography, we have made a simulating non-lens Fourier transform holography by using He-Ne laser, and reconstructed it by numerical image process. In this paper, we discuss several problems met in the experiment, such as blurring effect owing to vibration, the optimal distance Z between speciment and CCD receiving plane, and so on.
XUV spectroscopic study of laser-produced plasma
Author(s):
Jae-Hoon Kim
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Laser-produced carbon and boron plasmas were studied using an XUV flat-field spectrograph. The flat field spectrograph consists of a variable line spacing cancave grating, and detection system. For the collection of soft x-ray beam, toroidal mirror is used. Detectors used are photographic films for time integrated spectrum and a streak camera for time resloved spectrum.
Laser plasma x-ray source
Author(s):
Xiaofang Wang
Show Abstract
We summarize our studies on laser plasma x-ray emission, including the dependence of incoherent x-ray emission on atomic number, laser intensity, and target structure, and the exploration of coherent x-ray generation with lasing schemes and other approaches.
Gain optimization of C VI Balmer-a 182Aline in a z-pinch carbon plasma
Author(s):
K. T. Lee
Show Abstract
Small signal gain of H-like, C VI Balmer-α, 182Å line in a Z-pinch plasma is numerically studied to understand the behavior of the gain in the experimental parameter space and to get an optimized condition. A quasi-steady-state atomic code is implemented, which calculates the excited level populations of H-like ion and small signal gain of n = 3 → 2 transition in optically thin case. The developed hydrodynamic code evaluates the dynamics of the Z-pinch carbon plasma. Peak plasma current, Io and initial plasma density, No are changed for a given initial plasma radius, R and the period of plasma current, T. The gain as high as 20cm-1 is obtained for Io = 110kA,No = 2.5 × 1018cm-3,T = 400ns and R = 2.0mm.
Measuring refractive indices from interferograms in the soft x ray range
Author(s):
D. Joyeux
Show Abstract
The luminance1 of third generation synchrotron sources, (ALS, Elettra) and even some older ones such as NSLS (line X1A) ar BNL, and Super ACO (line 5U7) at Orsay which we are using, is now large enough to allow the practical construction of interferometers and transfer all applications of interferometry to the soft X ray domain (λ = 2-10 nm). Our purpose with the present work is to transpose to soft X rays the concept of measuring the real part n = 1-δ of the refractive index from the fact that interference patterns are shifted by eδ/λ fringes when a sample of thickness e is inserted in one arm of the interferometer. The n values of all materials in that range are quite close to unity and determination methods used so far are generally indirect and strongly affected by absorption. While of course a large imaginary part of the refractive index, i.e. the absorption, ultimately affects the interference contrast and therefore the accuracy, it does not affect the average value, which allows to expect a significant gain in accuracy from interferometry.
Ionization processes in a gas-puff z-pinch plasma
Author(s):
Seong Ho Kim
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A numerical study on an oxygen plasma produced in a gas-puff z-pinch(290kA with 1.2μsec risetime) has been carried out. We focused on the imploding phase and the simulation was compared with the measurement done by Foord et al. [1]. Our result shows that the possible driving source of the suggested ionization wave is the joule heating.
Atom driven by superstrong laser fields as a source of ultrashort-pulse XUV radiation
Author(s):
A. V. Kim
Show Abstract
Recent progress in the technique of generation and amplification of ultrashort laser pulses has resulted in the production of pulse duration of the order of or even shorter than 10 fs [1,2]. The use of Ti:Sa active crystals and broad-band optical elements, perfect compensation of wave dispersion in laser cavities and thorough comprehension of mode locking at self-focusing nonlinearity (Kerr-lens-mode-locking) have provided pulses having only few (∼3) optical cycles. Application of such a remarkable instrument opens up new prospects for experimental research on the interaction of ultrashort pulses with matter. It is also evident that a time has come for a serious theoretical analysis of these interaction models. Our report addresses the problem on nonlinear spectrum conversion of high intensity ultrashort laser pulses during the process of rapid optically-induced gas ionization.
Mo-Si multilayer as soft x-ray mirrors for the wavelengths around 20 nm region
Author(s):
Dong-Eon Kim
Show Abstract
Molybdenum-silicon multilayer soft x-ray mirrors have been fabricated using a magnetron sputtering system. Their structures have been characterized by x-ray diffraction (XRD) and reflectivities at normal incidence have been measured by using monochromatized synchrotron radiation in the 18-24 nm region. A normal incidence reflectivity as high as 40% at 20.8 nm was achieved.
Astigmatism-corrected flat-field XUV spectrograph and its aberration analysis
Author(s):
Il Woo Choi
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The astigmatism of a flat-field XUV spectrograph was compensated for by using a toroidal mirror. The aberration of the spectrograph system was analyzed from the wave front aberration. The performance of the spectrograph was investigated by obtaining spectra from plasmas generated by an iodine laser. The calculated and the experimental results show that the astigmatism is efficiently corrected over the entire wavelength range of 30-300 Å ; consequently, the spectrograph system can generate space-resolved spectra along the direction parallel to the grooves of the grating.
