Instabilities of a short-cavity standing-wave vibronic laser
Author(s):
Wojciech Gadomski;
Bozena Ratajska-Gadomska
Show Abstract
Self pulsing and chaotic dynamics of the short cavity vibronic alexandrite laser is reported. This phenomenon is explained by the process of energy pulling between the laser photons and the host crystal phonons.
Combined acousto-optic modelocker/electro-optic switch
Author(s):
Csaba Kuti;
Laszlo Turi;
Li Yan;
Chi Hsiang Lee;
Wei-lou Cao
Show Abstract
An optic-axis LiNbO3 sample has been supplied on the front part of its lateral x-faces with a pair of electrodes, while the rest of the y-faces along the optic-axis are also covered with electrodes. The rear electrodes are devoted to excite piezoelectrically a diffraction grating to modelock near-infrared lasers. The front electrodes form those of an electrooptic switch that is to coupled out the picosecond pulse developed during repeated round-trips in a closed laser cavity.
Laser action in resonators composed of scattering mesoscopic particles
Author(s):
Bernd Wilhelmi
Show Abstract
Mirrorless lasers composed of gain medium and scattering mesoscopic particles are dealt with, where the feedback arising from the arrangement of scatterers determines the parameters of emitted radiation, coherence included. Micro lasers consisting of two particles as well as complex highly ordered and random arrangements of particles have been investigated.
High-brightness white light source
Author(s):
Gabor Kurdi;
Karoly Osvay;
Zsolt Bor;
Istvan Ketskemety
Show Abstract
We present a simple but effective method to generate high brightness point-like white light source by tools available in almost every laboratory working in the field. Experiments were carried out resulting 161 nm wide flat top spectrum. Theoretical model also developed.
Stability of high-Q piezoresonators of standing-wave acousto-optic diffraction modulators
Author(s):
Csaba Kuti
Show Abstract
A significant improvement in the thermal and frequency stability of PESO (the PESO principle is light modulation by the direct Piezo-Electrically induced Strain-Optic effect) diffraction modulators applied successfully to modelock Nd- lasers can be achieved by forcing the self-stabilization mechanism activated by the temperature dependence of the resonance frequency.
Optimum operating conditions of a hollow-cathode Au-II laser
Author(s):
L. Szalai;
Tadeusz M. Adamowicz;
A. Tokarz;
G. Bano;
K. Kutasi;
Z. Donko;
Karoly Rozsa
Show Abstract
Laser operation on the Au-II 282.3 nm ultraviolet transition was obtained from a high-voltage, segmented hollow-cathode discharge tube. The excitation mechanism of the laser is charge transfer collisions of He+ ions and ground state Au atoms resulting from the sputtering of the gold- coated cathode. The high gain provided by the special hollow cathode construction made it possible to operate the laser with external mirrors on the ultraviolet 282.3 nm line. For the efficient pumping of the laser, high density of both He+ ions and Au atoms must be present in the discharge. Increased cathode sputtering, thus higher Au atom density can be achieved using a small amount of a heavier noble gas (e.g. Ar) in the helium buffer gas. On the other hand, the presence of Ar--due to its low ionization potential and high ionization cross section--reduces the energy of electrons and thus the ionization rate of helium. Measurements of the laser power and small signal gain indicate that the optimum partial pressure of argon is in the order of 0.25 - 0.75%.
Dynamic spread function of high-speed acousto-optic filter at high diffraction efficiency
Author(s):
Anatoly S. Zadorin;
Andrei S. Nemtchenko
Show Abstract
We developed a mathematical model of high-speed acoustooptic fiber, tunable by a linearly frequency modulated (LFM) signal at high efficiency of diffraction. It is shown that the dynamical dependence of the transmission coefficient of the filter is affected by the frequency tuning rate of the control LFM signal. This factor establishes the relation between filter spectral resolution and speed of operation. Formally, the relation is given by the filter transparency as a function of two arguments: time and tuning rate of the control signal. It is called the dynamical spread function (DSF). Analytical dependences are derived that govern the DSF shape in different regimes of non-collinear acoustooptic interaction.
Influence of light polarization on laser destruction
Author(s):
Gennady M. Mikheev;
Valentin S. Idiatulin
Show Abstract
The bending of the channel of laser destruction in metals and dielectrics is observed experimentally. The plane of bending is proved to be perpendicular to the polarization plane of the incident laser beam. It is shown that the bending is a result of the polarization dependence of the light reflectivity from the surface of the channel, but not of the intensity asymmetry in the beam crossection. Such asymmetry is essential for the choice of direction of bending in its plane only. The experimental results are substantiated by the theory of light reflectivity from absorbing media, they are in qualitative and quantitative accordance with each other.
All-optical transistor based on polarization plane rotation in a neodymium laser passively Q-switched with a Cr4+:YAG crystal
Author(s):
N. N. Il'ichev;
Alexander V. Kir'yanov;
Vicente Aboites
Show Abstract
A device is proposed which is based on the phenomenon of dependence of polarization state of a neodymium laser ((lambda) equals 1.06 micrometers ) passively Q-switched with a Cr4+:YAG crystal upon relative orientations of the switch and an intracavity partial polarizer. It is shown that such a device operates as an all-optical transistor. One of the main parameters (polarization) of the powerful neodymium laser can be controlled by the relatively weak signal delivered from a cw laser or laser diode, wavelength of which falls into the Cr4+:YAG crystal resonant absorption band (0.8 - 1.2 micrometers ).
Lasing efficiency spectra in dye lasers
Author(s):
A. Kukhto;
V. Galkin;
G. Shakkah
Show Abstract
The dependence of lasing efficiency on pumping wavelength in different dye solution lasers are found and studied for the first time. Doubled frequency of titanium-sapphire laser was used as a tunable pumping source. It is shown that maximal value of lasing efficiency is on a longwave shoulder of an absorption spectrum for all studied compounds. A mathematical modeling study was used in order to state the mechanism of lasing efficiency spectra forming. It was shown that these spectra are not due to singlet-singlet or triplet-triplet transient absorption. Such a behavior takes place at high solution concentrations, pumping densities and quality of a cavity.
New trends in nonlinear optics
Author(s):
Jan Boness;
Gerd Marowsky
Show Abstract
In this contribution new physical effects are presented which are observed when different materials are irradiated with high-intensity femtosecond laser pulses. A general classification of regions on the intensity scale is given and experimental results concerning higher-harmonic generation in high-Z materials with laser intensities exceeding 1019 W/cm2 are discussed. Two alternative approaches to the generation of such intensities are described.
Two-pass second-harmonic generation of ultrashort pulses
Author(s):
Jozsef A. Fulop;
Attila P. Kovacs;
Zsolt Bor
Show Abstract
Utilization of the dispersion of a prism pair for the enhancement of second harmonic generation in the two-pass arrangement is proposed. The second harmonic intensity is increased by a factor of four compared to that of the one- pass method, without the narrowing of the bandwidth. The calculations show that the arrangement can be used for efficient frequency doubling of 50-fs pulses at central wavelength of 800 nm.
All-optical inverter operating over a temperature range of -200oC to 750oC in erbium-doped borate glass
Author(s):
Yoshinobu Maeda;
Akio Konishi;
Hidekazu Hashima;
Hajimu Wakabayashi;
Toshikazu Yamada
Show Abstract
An all-optical inverter, which operates over a temperature range of -200 to 750 degree(s)C, was demonstrated in erbium- doped borate glass. The dependence of negative nonlinear absorption effect on sample temperature and modulation degree was investigated, using an 810.0 nm laser diode. Reversed-phase waveforms were observed in the transmitted waveform in the temperature range. The glass transition temperature was measured to be 708 degree(s)C by differential thermal analysis. With a decreasing modulation degree, the reversed-phase waveform was obtained. The effect has a characteristic which is almost independent of the sample temperature because it is formed by optical transitions of the inner shell of the erbium ion.
Optical quadropole sum-frequency generation of polarized waves via dipole-forbidden atomic transition
Author(s):
E. G. Kanetsian;
G. G. Adonts
Show Abstract
The process of collinear mixing of two frequencies in an external magnetic field in resonant systems is studied theoretically. It is suggested to provide the interacting wave phase matching by corresponding choice of sum-frequency between doublet splitting second excited state. The numerical estimations demonstrate the possibility of 1 - 5% power conversion.
Star states in multi-photon processes
Author(s):
Z. Kis;
Jozsef Janszky;
P. Adam
Show Abstract
It is shown that the classical and quantum mechanical description of first and second order nonlinear optical processes (including squeezing) are equivalent in the sense that in both cases an initial phase space distribution transforms in the same manner. We investigate in detail the degenerate three wave mixing, which is a third order process, and point out that the classical and quantum descriptions give essentially different results. This process yields three-pointed star states. It is pointed out that the efficiency of the star state in a three photon process is superior to that of a coherent state with two orders of magnitude.
Region of phase transition in optical bistable systems
Author(s):
Yurij V. Gudyma
Show Abstract
The threshold bistable system was investigated near a threshold of switching between phases. It was shown, that in spite of the fact that the equation, that describes this system does not have the stable localized structures among the solutions, envelopes of these solutions can form solitons of a nonlinear Schrodinger equations. Dynamic critical index was calculated near this point in the second order (epsilon) . It characterizes cross-section of scattering on fluctuation modes.
Nonlinear reflection of extremely short light pulses
Author(s):
Victor G. Bespalov;
Sergei A. Kozlov;
Alex O. Oukrainski;
Yuri A. Shpolyanskiy
Show Abstract
The reflection of intense laser pulses consisting only of several light field cycles from nonlinear, isotropic and transparent dielectric media is theoretically investigated. It is shown, that the spectrum of the reflected pulse is enriched by odd harmonics and at close linear refraction indices of bordering media the duration of the reflected pulse can become less significant than the duration of incident pulse. It is shown, that the intense refracted wave has a strongly asymmetrically broadened spectrum in nonlinear medium.
Laser material interaction technologies for materials processing
Author(s):
Yash P. Kathuria
Show Abstract
With the established technique of laser in science and industry, its applications have become diversified in the micro- and macro-processing areas. Three potential lasers CO2/Nd- YAG/Excimer operating in the ir and uv region have been applied in various domains covering different spectrum of industrial applications. Of this the processing with the CO2/Nd-YAG lasers usually considered as thermal processing covers mainly cutting/welding and surface modification areas. Whereas the excimer laser operating in the uv region and having a unique characteristics of cold ablation, allows the production of small um order microstructures. In all these processes the beam interaction time with the material greatly affects the structural development of the end product. The present paper elaborate a few of these basic processes and explore the possibilities of current and new application areas.
Atomic force microscope study of excimer-laser-treated graphite surfaces
Author(s):
Adam Mechler;
Peter Heszler;
Zoltan Kantor;
Tamas Szoerenyi;
Zsolt Bor
Show Abstract
Treating of highly oriented pyrolytic graphite surface by ArF excimer ((lambda) equals 193 nm) laser pulses above the ablation threshold, in the range of 0.4 and 4 J/cm2 laser fluences was investigated. Atomic force microscopy and area-selective Raman spectroscopy was used for the observation of the surface morphology and determination of the quality of the remaining material. At low (< 0.6 J/cm2) fluence a material removal rate of several monolayer per laser pulse was detected, without changing the quality of the remaining material. Irradiation at high (approximately 2 J/cm2) fluence resulted in ablation rates of the order of 10 nm/pulse and the formation of an approx. 300 nm thick diamond-like carbon film with approx. 50% concentration of the sp3 hybrid-states of carbon. The graphite structure of the laser-modified layer was perfectly recovered upon annealing the irradiated surfaces in air at 650 degree(s)C for 30 minutes.
Changes in optical properties of excimer-laser-irradiated polymers
Author(s):
Bela Hopp;
Zsuzsanna Marton;
Maria Csete;
Ferenc Ignacz;
Zsolt Bor
Show Abstract
Nanosecond resolution measurements were performed to investigate the change of reflectivity of polymers (PolyMethylMethacrylate and PolyImide) under ArF excimer laser irradiation. The temperature increase due to the irradiation was also calculated. From the results of the experiments and calculations we concluded that several processes influence the observed changes in optical properties of the irradiated polymer samples, such as the quickly expanding gas that leaves the surface immediately after the incidence of the excimer pulse, thermal decomposition of the surface layer and the decrease of the refractive index caused by the heat.
Smooth vanadium-nitride layers created on silicon substrates by pulse laser deposition method
Author(s):
Laszlo Nanai;
Robert Vajtai;
J. Kiss;
Armando Luches;
Ion N. Mihailescu
Show Abstract
Pulsed Laser Deposition (PLD) of vanadium-nitride (V2N, V10N7) films on Si substrates have been carried out under influence of series of UV (excimer) laser pulses ((lambda) equals 308 nm, (tau) FWHM equals 25 ns) in NH3 atmosphere of a few mbars. In the reaction cell the Si target has been placed to be parallel to V sheet at angle of 45 degree(s) to the incident laser beam, and the plasma plume induced by laser pulse reached the target close perpendicularly. The number of shots at fluxes of 30 J/cm2 were varied between 100 and 5000. Rutherford Back- Scattering studies revealed that under influence of laser pulses at Si layer V2N layers of 100 nm thickness were formed, while the composition of the layer closer atmosphere was V10N7 of 50 nm thickness (in average). In some cases we observed layers of VNCO and V10N7C5. Atomic Force Microscopy measurements revealed a formation of quite smooth surfaces with roughness of less than 10 nm. A characteristic wave-like structure with period of 3 - 5 nm was able to be observed in some cases. XPS examinations showed the existence of well defined peaks of V(2p) lines at 516 eV and 513 eV. Also we observed lines of N(1s) at 397 eV, O(1s) at 529 eV and C(1s) at 284 eV. From these investigations it might be concluded that PLD technique allows growing smooth VN layers on Si with a little, but measurable contamination of carbon and oxygen.
Mask-adapted beam shaping for materials processing with excimer laser radiation
Author(s):
Joerg Bernges;
Lars Unnebrink;
Thomas F. E. Henning;
Ernst Wolfgang Kreutiz;
Reinhart Poprawe
Show Abstract
Recent developments of non-rotationally symmetric optical elements (NOEs) for beam shaping in the field of material processing with excimer laser radiation are presented. The performance of a conventional faceted integrator and two faceted NOEs, designed to illuminate an annular aperture mask, are compared. Surface designs of the NOEs and results of material processing (ablation of polyimid foil by KrF excimer laser radiation) are presented. By mask adapted beam shaping NOEs improve the total transmission of the optical system.
Femtosecond UV-laser ablation of solid targets
Author(s):
Peter Simon
Show Abstract
Ablation of submicron structures on metals and semiconductors by short ultraviolet laser pulses (0.5 - 50 ps, 248 nm) is presented. Features like periodic line structures with a line-spacing below 400 nm, and holes with diameters well below 1 micrometers are produced on the sample surface by single laser shot exposure. The structures are projection printed by a Schwarzschild-objective (NA equals 0.4) in air environment. The dynamics of the surface modification has been studied using a pump-probe technique. The ablated grating structure is illuminated with a second, weak probe pulse (500 fs at 496 nm) whose diffracted light (0th, 1st, 2nd order signals) is recorded as a function of the delay between the two pulses. The results provide valuable time- resolved information about the change of the surface morphology.
Nickel deposition on silicon surfaces
Author(s):
Cs. Beleznai;
Laszlo Nanai;
Seppo Leppaevuori;
Janne Remes;
Hannu Moilanen;
Thomas F. George
Show Abstract
Experimental results of laser assisted chemical vapor deposition of nickel from Ni(CO)4 and theoretical treatment of deposition process are presented. The nickel deposition has ben realized by scanning of Ar+ laser beam (100 - 400 mW, (lambda) equals 515 nm and 488 nm) on Si surfaces in atmosphere of Ni(CO)4 with 0.2 - 2.0 mbars with scanning speeds of 20 - 700 micrometers /s. As a result homogeneous Ni lines on Si have been deposited with a typical volumetric growth rate of 250 micrometers 3/s and widths of 10 - 20 micrometers and thickness of 0.2 - 0.5 micrometers . The electrical resistivity of lines deposited was cca 7 (mu) (Omega) cm. The theoretical treatment includes computations of the temperature distribution in both gas- phase and solid substrate. The reaction rate is computed on base of local concentration and local temperatures, within the frame of finite element methods using triangles as a base of computing.
Development of submicrometer periodic surface structures on polyethylene terephthalate
Author(s):
Maria Csete;
Zsolt Bor
Show Abstract
Submicrometer Laser Induced Periodic Surface Structures (LIPSS) were generated on polyethylene-terephthalate (PET) using polarized beam of an ArF excimer laser, having a fluence of 4 mJ/cm2. Atomic Force Microscope and a home made repositionable sample holder was used to follow the morphological changes on the same part of the surface shot by shot. The main phases of the structure formation process were described: light scattering on the granulates which exist also on the original PET surface; appearance of additional granules and formation of elliptical modulation around the granules; transformation into ripple-shape modulation. The dependence of the LIPSS period on the wavelength and on the angle of incidence was determined. The LIPSS generating feedback mechanism was described as the interference between the incoming and surface-scattered waves in the light modified region. It was shown that the LIPSS is a self-organized grating.
Ripple formation on GaAs surfaces by ultrafast (fs) laser pulses
Author(s):
Laszlo Nanai;
Robert Vajtai;
L. Fabian;
Sandor Szatmari;
Seppo Leppaevuori;
Thomas F. George
Show Abstract
We have observed an appearance of a wavelike (ripple) structures on GaAs due to influence of ultrafast (fs) laser pulses. Optical and atomic force microscopy studies revealed the double wavelength characters of ripples inside and outside of the illuminated areas. Raman investigations showed the existence of zinc-blend to cubic transitions in crystalline symmetry at the peripherical part of the irradiated area.
Excimer-laser-beam homogenization for materials processing
Author(s):
Lars Unnebrink;
Thomas F. E. Henning;
Ernst-Wolfgang Kreutz;
Reinhart Poprawe
Show Abstract
The paper presents an analysis of non-imaging integrators, which can be used for laser beam homogenization for materials processing with excimer laser radiation. A model for the transversal degree of coherence of the laser radiation is presented in order to estimate the performance of the integrating devices for the partially coherent excimer laser radiation. This is necessary for a more relevant design of those elements than a design by geometric optical means only.
High-optical-quality LiNbO3 thin films obtained by pulsed laser deposition
Author(s):
D. Ghica;
Mariuca Gartner;
F. Ciobanu;
V. Nelea;
C. Martin;
Ion N. Mihailescu
Show Abstract
We report the successful growth of high optical quality LiNbO3 thin films (high birefringence and good transparency over the entire visible spectral range) by pulse laser deposition (PLD) on Si substrates. PLD of a LiNbO3 single-crystal target was carried out using a KrF* excimer laser ((lambda) equals 248 nm, E equals 80 mJ, (tau) equals 20 ns, v equals 2 Hz). The thin films have been deposited in oxygen and, for some of them, a thermal treatment has been applied in an oxygen atmosphere. The thin films have been characterized by grazing incidence X-ray diffraction, spectroscopic ellipsometry and Fourier transform infrared spectroscopy.
Laser interaction with carbon-type materials
Author(s):
Milesa Z. Sreckovic;
B. Kaludjerovic;
S. Bojanic;
N. Ivanovic;
V. Rajkovic;
S. Ristic;
Z. Fidanovski
Show Abstract
It is well known that application of stimulated light may influence phase modifications and changes of carbon structure. These effects of laser irradiation, in different working regimes and atmospheres, are widely investigated for fullerenes and diamond structure, but for many other carbon materials, are not. In the presented experiments, we treated by Q-switch ruby and Nd3+ YAG laser beams different carbon clothes, produced by pyrolysis (T <EQ 1000 degree(s)C) of cellulose materials in inert atmosphere. The materials are interesting for many applications, including medical. The laser pulse energy was of order of 0.1 - 1 J, in one, or multi-pulse regime. Focused and unfocused beams were used to induce damages and oxidation of sample surfaces. the damages were analyzed by scanning electron microscopy and specific area is measured by Brunauer, Emmet and Teller method, before and after the interaction. Materials exhibited differences in the damaging level and the fiber breaking thresholds. Mechanisms of laser interaction leading to oxidation of carbon type materials are discussed, and the necessary experimental conditions for intended changes are analyzed.
Laser-assisted chemical vapor deposition of diamond microstructures
Author(s):
Zsolt Toth;
Adam Mechler;
Peter Heszler
Show Abstract
High quality diamond has been deposited area selectivity onto thin tungsten films layered onto fused silica substrates in a hot filament CVD reactor. The deposition method uses a hot filament process which is combined with localized heating by a focused Nd-YAG laser beam.
Ultrafast photographic investigation on laser ablation of liquid metals
Author(s):
Zsolt Toth;
Tomi Smausz;
Bela Hopp;
Ferenc Ignacz;
Zoltan Kantor;
Tamas Szoerenyi;
Zsolt Bor
Show Abstract
The application of laser pulses as `photographic flash' gives the possibility to record ultrafast phenomena. Since the duration of the laser pulses may be tuned from fs to cw, it is easy to choose a right laser source to resolve the time domain to be investigated. In this study excimer laser ablation of molten metal targets was followed by ultrafast photography based on delayed dye laser pulses. Molten tin and bismuth were ablated in vacuum by an ArF excimer laser. Pictures of the surface and the ablated material were taken at different moments after the start of the excimer laser pulse with temporal resolution of 1 ns. The series of snapshots contain information on the initial phase of plume formation in the ns time regime, and on liquid motion (surface waves, protuberances, liquid jet formations, splashing) in microsecond time scale. The important result of this study is the registration of the processes leading to droplet emission from the ablated target surface, because the elimination of droplets is a crucial requirement in depositing thin films by the pulsed laser deposition technique.
Modified method for analysis of distorted quasi-periodical images
Author(s):
Vladislav Krzyzanek
Show Abstract
2D reconstruction of continuously distorted quasi-periodical images is discussed. The use of classical methods, the method of modification of spatial-frequency spectrum and the method of correlation averaging, give accurate results only for images with very small distortion. In the paper the methods are modified by the use of a simple technique for elimination of the distortion and formula for correlation.
Optical-logic element using array of computer-generated Fresnel holograms
Author(s):
Kunihiko Mori;
Izaiku Noritake
Show Abstract
The array of computer-generated Fresnel holograms is investigated for an optical-logic element, and a 2-input AND optical-logic element was designed. Two coded input is applied to proposed optical-logic element and arbitrary coded output is reconstructed by the element. All logic and multi-input element can be realized by proposed method. An array of optical-logic elements for parallel processing is also possible easily by using proposed optical-logic element.
Concept of a neural system for real-time evaluation of spectroscopic measurements
Author(s):
L. Redei;
Miklos Fried;
Tivadar Lohner;
O. Polgar;
Istvan Barsony;
Sz. Forizs;
Zoltan G. Horvath;
Josef Humlicek;
H. Wallinga
Show Abstract
A hardware implementation of a Backpropagation feedforward neural network has been designed. The tool was proposed for reflectometric measurements integrated together with photosensor arrays. The intelligent reflectometric sensor is being implemented in a multi-chip-module approach. A logarithmic input transformation is applied for easing the misalignment and parameter scatter correction. It also allows for easy ratio calculation by subtraction for normalization with the reference value. The neural network was designed for complexities up to 100 inputs, 30 hidden neurons and 5 outputs. The digital building blocks (neurons) utilize a logic approximation of the sigmoid nonlinearity and the possibility of weight scaling. These hardware solutions result in a simultaneous area reduction and speed gain, at the cost of slightly decreased performance. Simulations of the proposed neural system prove applicability for evaluation of optical measurements were performed for reflectometric and ellipsometric data thin porous layers. Hardware simulations showed good correspondence to the optimum-case neural software simulations.
Optical recording in nanolayered amorphous chalcogenide films
Author(s):
Alexander A. Kikineshy;
Alexander Mishak;
Vasil Palyok;
Miroslav Shipljak
Show Abstract
New possibilities of tailoring the parameters of light sensitive media, based on the compositionally modulated As2S3, Se1-x(Te,As)x chalcogenide glasses and a-Se multilayers are developed. Quantum confinement effects, the change of optical and thermodynamical parameters, as well as interdiffusion processes are found to be involved to the change and improvement of the amplitude- phase optical recording.
Nonfeedback nonlinear holographic associative memories
Author(s):
Peter V. Polyanskii
Show Abstract
Several original versions of nonlinearly recorded hologram- based associative memories are summarized. All of them are realized using phase-conjugate properties of such holograms being associated just with nonlinear part of a holographic recoding. The photorefractive prototypes of some represented memories are pointed out. The introduced all-optical associative memories exhibit error-correcting properties, ability to edge enhancement into associative responses, and may be realized at arbitrary recording media (thin or volume, permanent or reversible).
Phase-conjugation cryptography using nonlinearly recorded holograms
Author(s):
Peter V. Polyanskii
Show Abstract
Implementation of an all-optical cryptograph with a double- random phase coding using nonlinearly recorded holograms is considered. This implementation is based on recently discovered ability of a nonlinearly recorded hologram with the standing reference wave to self-conjugate an object beam of arbitrary completeness. It is shown, that large apertures of a quibic hologram-based phase conjugate mirror permits to overcome the main practical difficulty hindering implementation of a double-random phase coding cryptography through diminishing the information losses due to spatial- frequency filtering of the time-inverted replica of the stored memory.
Edge-enhanced phase conjugation based on a quadric hologram
Author(s):
Galina V. Bogatiryova
Show Abstract
Two versions of a quadric hologram-based edge-enhancing phase conjugation are introduced. Self-conjugation of an edge diffraction wave from a profiled knife-edge is implemented using a quadric hologram recorded with a standing reference wave. Double phase conjugation among two mutually incoherent (noninterfering) input signals recorded with counterpropagating reference beam is also grounded and demonstrated. Both versions are explained as the result of spatial-frequency heterodyning (nonlinear mixing) of partial cross-gratings provided by the holographic recording nonlinearity. Edge enhancement of the conjugated responses of a quadric hologram is shown to be the consequence of the Young-Rubinowicz's model of diffraction phenomena.
Directional multiplexing for optical board-to-board interconnections
Author(s):
R. Klug;
U. W. Krackhardt;
K.-H. Brenner
Show Abstract
The propagation angle of a beam is conserved when traveling through a multi-mode step-index fiber over short distances. We show that this feature can be used for multiplexed signal transmission thus providing a high bandwidth single-fiber interconnection between chips, boards or racks. With respect to this application the transmission properties of a fiber are analyzed. Concepts for optical multiplexing and de- multiplexing set-ups are outlined. A fiber transmission line consisting of a fiber and an optical de-multiplexing unit is characterized to obtain experimental results on the transmission capabilities in terms of efficiency, channel separation, number of multiplexed channels and cross-talk.
Double matched filtering using the photorefractive Bi12TiO20 crystal at lambda = 0.633 um
Author(s):
Paulo Acioly M. dos Santos;
Gilder Nader;
Alberto A. Tagliaferri
Show Abstract
In the present paper a double correlator system is proposed. This double Vander Lugt correlation system uses both dynamic photorefractive and a slow complementary holographic processing. The system shows a good discrimination capacity and employs only one bulk photorefractive sample, the Bi12TiO20 crystal at (lambda) equals 0.633 micrometers , in diffusion-only recording mechanism.
New frontiers of elastic light scattering in aerosols
Author(s):
Wladyslaw W. Szymanski
Show Abstract
Aerosol particle size distribution and concentration are likely the most frequently measured aerosol parameters. In this contribution some methods for determination of aerosol particle size, concentration and refractive index based on the elastic light scattering will be presented. At relatively low concentrations single particle measurement can be applied. An innovative optical system based on a bi- angular scattering from single particles and providing a real-time access to the real and imaginary part of the refractive index of aerosol particles is discussed. The accuracy of the technique has yet to be explored but preliminary findings are presented. Beyond concentration levels of about 103 cm-3 integral observation methods on an ensemble of particles must be used and require usually empirical calibration procedures. A method allowing an absolute, calibration free optical determination of aerosol concentrations up to the order of 108 cm-3 based on a simultaneous measurement of scattered and transmitted light fluxes is presented. Combining elastic scattering measurement with a condensational growth of aerosols gives an access to size distribution of particles based on Kelvin equivalent sizing starting from about 10-3 micrometers in particle radius. The results show that elastic light scattering methods provide a possibility for a real time sizing of aerosols in the size range from about 10-3 micrometers stretching over more than 4 orders of magnitude, for concentration determination starting from single particle counting to about 108 cm-3 and for an assessment of optical properties of aerosols which, if linked with their chemical character, could also have a substantial contribution to industrial and environmental issues.
New 3D robotic vision system
Author(s):
Mohamed R. Arshad;
J. Lucas
Show Abstract
This paper presents a new robotic vision system based on the Time of Flight technique. It provides the range information at pixel level and a scanning function to acquire the image. The system consists of an internally modulated laser as the source, an image dissector camera tube with pixel resolution, a phase measuring unit and a host PC with associated interface boards. The laser source provides a maximum power of 10 mW at 670 nm wavelength ((lambda) ). A modulation frequency in the MHz region has been used. The range information was obtained by measuring the phase difference between the transmitted and the received signals, using a high frequency phasemeter circuit. The robotic vision system has been tested in various experimental set- ups. It has been successfully used to obtain range images of a variety of scenes. From the results, it is concluded that the robotic vision system has the potential for a wide range of applications.
Nature of radiation absorption centers in silica glass
Author(s):
Vladimir A. Saetchnikov;
Elina A. Chernyavskaya;
Tatjana P. Yanukovich
Show Abstract
Optical fibers as detectors of radiation have a lot of advantages: big length, little diameter, no electrical interference, and an opportunity to measure radiation from the spread source. Optical characteristics of pure silica glasses as a material for optical fibers are very important. Spectroscopic parameters of high-purity silica glasses made by sol-gel technology have been investigated. Absorption bands are formed near 4.6, 2.0, 1.7 eV when glasses are subjected to (gamma) -rays. This absorption bands are considered to be due to nonbridging oxygen hole centers (NBOHC). Dependence of integral absorption in the bands on irradiation dose for different samples of high-purity silica glass was received. Integral absorption in 4.6 eV-band increased with increasing of dose. And integral absorption in 2.0 eV-band also increased with increasing of dose, but position of its maximum shifts to smaller value of energy in samples with great content of oxygen. This shift is explained by increasing of absorption in 1.7-eV band. The experimental data gives that absorption bands are determined by presence of different types of NBOHC in the sample. Absorption band near 2.0 eV is due to NBOHC equalsVSi-O(arrow up). Absorption band near 4.6 and 1.7 eV is due to NBOHC equalsVSi-O-. The intensity of absorption band near 1.7 eV is determined by concentration of oxygen in the sample.
Optical constants of thin CVD-Tungsten oxide films
Author(s):
Anna M. Szekeres;
D. S. Gogova
Show Abstract
CVD-tungsten oxides were obtained at 300 degree(s)C on glass substrates by pyrolitical decomposition of W(CO)6 vapor in argon/oxygen stream at atmospheric pressure. The thin films were examined by spectroscopic ellipsometry in the wavelength range of 0.3 - 0.8 micrometers . It was found that as- deposited oxides are rather porous and predominantly amorphous but crystalline phase is also present. During the annealing at 450 and 500 degree(s)C the oxide becomes fully crystallized and yet it preserves its porosity. The high level of porosity is reflected in the low values of the refractive indices (1.9 - 1.5) and the optical band gap energies (3.04 - 3.11 eV).
Fiber optic sensors and systems at the Federal University of Rio de Janeiro
Author(s):
Marcelo Martins Werneck;
Paulo Acioly M. dos Santos;
Aldo Pacheco Ferreira;
Luis E. Maggi;
Carlos Roberto de Carvalho Jr.;
R. M. Ribeiro
Show Abstract
As widely known, fiberoptics (FO) are being used in a large variety of sensors and systems particularly for their small dimensions and low cost, large bandwidth and favorable dielectric properties. These properties have allowed us to develop sensors and systems for general applications and, particularly, for biomedical engineering. The intravascular pressure sensor was designed for small dimensions and high bandwidth. The system is based on light-intensity modulation technique and uses a 2 mm-diameter elastomer membrane as the sensor element and a pigtailed laser as a light source. The optical power output curve was linear for pressures within the range of 0 to 300 mmHg. The real time optical biosensor uses the evanescent field technique for monitoring Escherichia coli growth in culture media. The optical biosensor monitors interactions between the analytic (bacteria) and the evanescent field of an optical fiber passing through it. The FO based high voltage and current sensor is a measuring system designed for monitoring voltage and current in high voltage transmission lines. The linearity of the system is better than 2% in both ranges of 0 to 25 kV and 0 to 1000 A. The optical flowmeter uses a cross-correlation technique that analyses two light beams crossing the flow separated by a fixed distance. The x-ray image sensor uses a scintillating FO array, one FO for each image pixel to form an image of the x-ray field. The systems described in these paper use general-purpose components including optical fibers and optoelectronic devices, which are readily available, and of low cost.
Time-domain and spectral-domain low-coherence interferometry applied to dispersion measurements of optical fibers
Author(s):
Petr Hlubina
Show Abstract
Successful applications of low-coherence interferometry both in the time and spectral domains are demonstrated in the evaluation of the group optical path difference (OPD) between two linearly polarized (LP) modes of an optical fiber excited by a multimode laser diode TOLD 9201. Firstly, the visibility of spatial interference fringes is measured in a tandem configuration of a Michelson interferometer and a two-mode optical fiber under test as a function of the OPD in the interferometer. From the visibility dependence, the group OPD between two LP modes of the optical fiber is obtained. Secondly, using the same exciting source TOLD 9201, the wavelength-dependent modulation of the source spectrum is obtained at the output of the two-mode optical fiber. By processing ten measured spectral modulations using the Fourier-transform method, the wavelength dependence of the group OPD between two LP modes is obtained and good agreement with time-domain measurement is confirmed. When a halogen lamp is used as an exciting source, the wavelength- dependent modulation is resolved only in the vicinity of the equalization wavelength, where the period of modulation is sufficiently large to be resolved by the spectrometer. From the corresponding dependence, a value of the equalization wavelength of two LP modes of the optical fiber is obtained.
Real-time trichromatic holographic interferometry: preliminary study
Author(s):
Felix Albe;
Myriam Bastide;
Jean-Michel Desse;
Jean-Louis H. Tribillon
Show Abstract
In this paper we relate our preliminary experiments on real- time trichromatic holographic interferometry. For this purpose a CW `white' laser (argon and krypton of Coherent- Radiation, Spectrum model 70) is used. This laser produces about 10 wavelengths. A system consisting of birefringent plates and polarizers allows to select a trichromatic TEM00 triplet: blue line ((lambda) equals 476 nm, 100 mW), green line ((lambda) equals 514 nm, 100 mW) and red line ((lambda) equals 647 nm, 100 mW). In a first stage we recorded a trichromatic reflection hologram with a separate reference beam on a single-layer silver-halide panchromatic plate (PFG 03C). After processing, the hologram is put back into the original recording set-up, as in classical experiments on real-time monochromatic holographic interferometry. So we observe interference fringes between the 3 reconstructed waves and the 3 actual waves. The interference fringes of the phenomenon are observed on a screen and recorded by a video camera at 25 frames per second. A color video film of about 3 minutes of duration is presented. Some examples related to phase objects are presented (hot airflow from a candle, airflow from a hand). The actual results show the possibility of using this technique to study, in real time, aerodynamic wakes and mechanical deformation.
Dielectric properties of sol-gel TiO2(La) films
Author(s):
Mariuca Gartner;
Constanta Parlog;
Anna M. Szekeres;
S. S. Simeonov;
E. Kafedjiiska;
Toma Stoica
Show Abstract
High dielectric TiO2(La) films deposited on the silicon waves by the sol-gel technique have been characterized by Spectroscopic Ellipsometry, Fourier Transformed Infrared Spectroscopy. Rutherford Backscattering Spectroscopy and electrical measurements. The microstructural, optical and electrical properties exhibit a strong dependence on the introduced lanthanum quality. For La/Ti > 0.1 all film properties are abruptly changed closer to that of pure lanthanum oxide.
Optical characterization of diffuser-input standard irradiance meters
Author(s):
George P. Eppeldauer;
Miklos Racz;
Thomas C. Larason
Show Abstract
Standards quality irradiance meters have been developed at the National Institute of Standards and Technology to realize a detector based spectral irradiance scale. The design criteria and the optical and radiometric characterization of diffuser-input irradiance meters are discussed. The input geometry optimization is described for a broad-band InGaAs irradiance meter when measuring a 2856 K incandescent light source. The directional responsivity of the fabricated InGaAs and Si irradiance meters matches the cosine function with a maximum deviation of 0.15% within a 12 degree(s) field-of-view. Irradiance from sources of different sizes (incident beams with different f/numbers) can be measured over a wavelength range of 350 nm to 1800 nm.
New sizing method for liquidborne particles with high dynamic range
Author(s):
Aladar Czitrovszky;
Attila Nagy;
Tamas Mosoni;
Peter Jani;
Karoly Bodnar;
Arpad Illes
Show Abstract
A new liquid-borne particle counters is described that utilizes an optimized optical set-up to determine the size distribution and concentration by two different methods and to estimate the shape-factor of the suspended particles. The aim of this optimization was to achieve the appropriate optical conditions for such type of measurement, viz. determining the geometry of the illumination and detection, and calculating the testing volume and dependence of the parameters of detected signal on the particle size for pulse height and pulse duration methods performed at the same illumination and detection conditions. The main benefit of the developed device is the high dynamic range of the size determination of the micron-size liquid-borne particles and the possibility of estimating their shape-factor. The proposed measurement method was incorporated in a PC- controlled LQB-1-200-L-T liquid-borne laser particle counter developed on the basis of previous APC-03-2 and APC-03-2A air-borne particle counters and a LQB-1-200 liquid-borne particle counter.
PC-controlled CCD-matrix-based optical multichannel analyzer for RESPECT measurements
Author(s):
Sz. Forizs;
Zoltan G. Horvath;
Tivadar Lohner;
Miklos Fried;
Istvan Barsony
Show Abstract
The development of a special optical multichannel analyzer (OMA) has been finished in the frames of a COPERNICUS project. The aim of our present work is to recall the attention to some of the unique benefits of 2D CCD detector matrices in OMAs in contrast to the usual line detectors. We demonstrate the relatively simple hardware and software reconfiguration possibilities of our new OMA system to achieve the establishment of a problem oriented, neural network evaluated, low cost multichannel analyzer.
Characterization of a new computer-ready photon counting system
Author(s):
Gyorgy Andor
Show Abstract
The photon-counting system seems to be the best solution for extremely low optical power measurements. The Hamamatsu HC135 photon counting module has a built-in high-voltage power supply amplifier, discriminator, micro-controller with an RS232 serial output. It requires only a +5V supply voltage and an IBM PC or compatible computer to run. The system is supplied with an application software. This talk is about the testing of the device.
Real-time high-resolution absolute distance measurement by two-wavelength interferometry using superheterodyne detection
Author(s):
Toshiyuki Yokoyama;
Tsutomu Araki;
Shuko Yokoyama;
Norihito Suzuki
Show Abstract
A new method of high-resolution two-wavelength interferometry was proposed for real-time and absolute measurement of micron-order distance or step-shapes in the depth. Simultaneous phase measurement of synthetic wavelength and one of two wavelengths was executed to measure the distance in the range of synthetic wavelength with interferometric resolution. A heterodyne light source constructed of two longitudinal modes was also proposed. The intermode beat of two modes was used as heterodyne career. Experiments were done with He-Ne lasers of 633 nm and 544/612 nm to measure 3 - 18 micrometers range.
Orientation of optical transitions of pigments in isolated photosystem I particles
Author(s):
Atanaska Andreeva;
Maya Velitchkova
Show Abstract
In order to obtain information about the orientation of the photosynthetic pigments in respect to the membrane and their mutual orientation in photosystem I (PS I) particles, a new formula for the fluorescence anisotropy at low temperatures in oriented complexes is derived. The calculation are based on the consideration of PS I complex as a oriented triple- chromophore complex with energy transfer under steady-state excitation. Assuming perfect orientation of the complexes, a dependence of the fluorescence anisotropy on the polarization of the linearly polarized exciting light is obtained. Based on the derived formula both the orientation of the absorbing photosynthetic pigments in respect to the membrane and their mutual orientation can be determined using steady state polarized fluorescence spectroscopy with a different polarization of the linearly polarized exciting light.
Scanning optical interferometry microscopy, using optical fiber probe
Author(s):
E. G. Hassan Fatemi
Show Abstract
The aim of this report is to introduce a new method of scanning optical fiber microscopy, in which a single-mode optical fiber probe for studying the optical and topographical properties of a sample is used. It operates based on an interferometry technique that is named Fiber Probe Interferometric Microscopy (FPIM). The intensity of the light coupled into the fiber probe is modulated by the properties of the sample such as the local reflectivity, tilting and the distance between the radiating end of the fiber and the sample. The geometry of the envelopes of the interference intensity fringes caused by axially translating sample, at any location, is considered as a powerful measuring tool. FPIM system and technique for measuring the mentioned quantities are explained.
Application of optical spectroscopy in stellar dynamics
Author(s):
J. Vinko;
Laszlo B. Kish;
G. Kaszas;
G. Furesz
Show Abstract
We present examples of recent results based on optical spectroscopy of variable stars obtained at David Dunlap Observatory, Canada. The used spectrographs were the cross- dispersed echelle and the 1D Cassegrain mounted on the 1.88 m telescope. Several types of variable stars including contact binaries, Cepheid-type pulsating stars as well as recent extragalactic supernovae were observed. These examples illustrate the usefulness of precise optical spectroscopic measurements in stellar astrophysics.
Development and application of external-cavity diode laser systems for photoacoustic gas detection
Author(s):
Janos Sneider;
Zoltan Bozoki;
Arpad Mohacsi;
Miklos Szakall;
Gabor Szabo;
Zsolt Bor
Show Abstract
Two external cavity diode laser systems operating at 860 nm and at 1125 nm have been developed and assembled into photoacoustic gas detection systems. Both laser systems have been found to be suitable for water vapor detection applications. Comparison of the two systems has been made regarding their stability, mode structure, tunability etc. Their performance has been compared with other type of diode lasers as well.
Optimization of diode-laser-based photoacoustic laser systems for high-sensitivity detection of water vapor, methane, and carbon dioxide
Author(s):
Janos Sneider;
Zoltan Bozoki;
Arpad Mohacsi;
Miklos Szakall;
Gabor Szabo;
Zsolt Bor
Show Abstract
Developments towards a portable sensor system for in-situ detection of low concentration of water vapor are described. The system consists of a Littman type external cavity diode laser light source operating around 1125 nm, an acoustically optimized high sensitivity measuring photoacoustic ell, a reference photoacoustic cell, home made electronics and a personal computer for measurement and system control. For high sensitivity water vapor detection a fully computerized measurement protocol has been developed. Test measurements demonstrated that the system is able to detect water vapor concentration below the 10 ppm level.
Possible application areas of a diode-laser-based photoacoustic gas detection method
Author(s):
Janos Sneider;
Zoltan Bozoki;
Miklos Szakall;
Arpad Mohacsi;
Zsolt Bor;
Gabor Szabo
Show Abstract
Due to its simplicity, high sensitivity, reliability and low price diode laser based photoacoustic gas detection can be expected to gain more and more widespread applications in the close future. Examples of the possible application areas such as environmental monitoring, agriculture, medical science chemical process control etc. are discussed here.
One-beam digital speckle interferometry applied to semimentation in fluids investigations
Author(s):
Ilia Roussev;
Evtim Toshev;
Pavel I. Koulev;
Todor Partalin;
Violeta Madjarova
Show Abstract
A fully-automated version of the Speckle Photography based on the Fast Fourier Transform, the One-Beam Digital Speckle- Interferometry, is used for investigation of sedimentation. The study is carried out with a Hele-Show cell. Both qualitative and quantitative results of slow sedimentation of spherical glass particles in mineral oil are presented. In the present article the processes of so called `fingers' formation and its development (the sedimentation front already lost its stability) are investigated. The authors paid also attention to the uniform sedimentation after the fingers fall down on the cell's bottom.
Real-time holographic polarization fringes for stress and strain analysis
Author(s):
Paulo Acioly M. dos Santos;
L. C. da Silva Nunes;
Alberto A. Tagliaferri
Show Abstract
In this work we show a real time holographic polariscope. The new system is based on the dynamic anisotropic diffraction properties that happen in cubic photorefractive crystals of the sillenite family. This result represents a promising technique for possible mechanical strain and stress analysis for scientific and technical applications. The observations about the performance and the behavior of the proposed system was made in diffusion only recording mechanism in the photorefractive crystal Bi12TiO20 illuminated by (lambda) equals 0.633 micrometers from a He-Ne laser light source.
Real-time cross-correlation interferograms for flowmeter application
Author(s):
Paulo A. M. dos Santos;
L. C. da Silva Nunes;
Marcelo M. Werneck;
N. A. Sigaki
Show Abstract
In the present work real time interferograms operations are proposed as solution in flowmeters applications. Cross correlation interference patterns are discussed and proposed as possible physical tools to solve this problem. This experimental proposal is particularly important when micro turbulence produce extremely localized phase mismatch in coherent light beams due to little index refraction variations in the flow channel.
Characterization of laser-generated microplasmas for use in quantitative analysis of liquids
Author(s):
Jozef Kaiser;
Miroslav Liska;
Ota Samek;
Pavel Knoll
Show Abstract
We report on the application of the technique of Laser Induced Breakdown Spectroscopy (LIBS) for the analysis of liquids. The technique of LIBS offers a fast, simple, real- time method of elemental analysis. With our simple LIBS set- up numerous elements, including the alkali and alkaline earth metals, and a range of toxic heavy metals, have been measured over a wide range of concentrations. In order to provide quantitative data in the evaluation of laser generated plasmas, parameters such as electron densities, plasma temperature, line shape functions, and others need to be measured. The method of measurement utilized in this study is primarily based on the analysis of the hydrogen Balmer lines which exhibit linear Stark broadening. Ca and Al lines, which exhibit quadratic Stark broadening, were also used. During the measurements it also must be established that the plasma is optically thin, and that the assumption of the existence of Local Thermodynamic Equilibrium is valid. Calibration curves for elements such as Na, Ca, Li, Mn, K, Cr, Al, Pb and Cu using H(alpha ), H(beta ) and H(gamma ) lines as a reference and calibration curves for Ca, Cu, Mn, Li and Na using carefully chosen elements as a reference elements added at `reference concentration' were obtained. Emphasis is placed establishing plasma diagnostics for use in non-laboratory environments, for example for the analysis of pollutants in water in harsh environments. Consequently, all spectroscopic measurements were made under standard atmospheric pressure conditions.
Optically induced rotation of combined Mie particles within an evanescent field of a Gaussian beam
Author(s):
Y. G. Song;
Soo Chang;
Jae Heung Jo
Show Abstract
We demonstrate a windmill type rotation of combined Mie particles caused by the evanescent field generated at the surface of a Gadolinium Gallium Garnet prism where a linearly polarized Nd:YAG laser beam (of wavelength 532 nm and power 100 mW) is totally reflected. The combined particles (e.g., doublets, triplets or quadruplets) consisting of polystyrene latex (or yeast) spheres with diameters of 3 - 5 micrometers are reported to rotate at 0.1 - 1 rpm in water when the particles are slightly displaced from the center of the evanescent field.
Makyoh-topography studies of mirrorlike surfaces: toward a quantitative understanding
Author(s):
Ferenc Riesz
Show Abstract
A quantitative approach to the Makyoh-topography image formation mechanism is presented. General relations are given on the optical settings. Then, optical ray-tracing simulations of an isolated defect (hillock or depression) and a periodic (sinusoidal) surface are presented for different optical settings. Optimum working conditions are established, and general features of the imaging are pointed out. Supporting experimental images of semiconductor samples are shown.
Optical investigations of polyethylene microporous films during the structure formation process
Author(s):
Galina C. Elyashevich;
Alexander G. Kozlov;
Ivanka T. Moneva;
Alexander A. Zinchik;
Alexander V. Smirmov;
Sergey C. Stafeev
Show Abstract
The structural investigations at each stage of the structure formation process--melt extrusion, annealing, and uniaxial extension--have been carried out for polyethylene microporous samples by light scattering, small-angle X-ray scattering, and birefringence techniques. The birefringence values (Delta) n have been calculated from the angular dependences of the transmitted polarized light intensity. The dependences of (Delta) n on the orientation degree (lambda) have been obtained. The basic characteristics of the crystalline structure and their changes at each stage of the process have been determined by the X-ray technique. Light scattering pictures have been obtained for microporous films using a laser with the wavelength of 633 nm. These pictures are characterized by a specific type of symmetry and differ from any patterns typical for oriented crystallizable polymers. It is found that similar pictures are observed for all porous samples regardless of their orientation degree. So it is possible to make a conclusion that the characteristic size calculated from the light scattering patterns may be regarded as one of the main topological parameters describing the disposition of pores as the scattering elements.
Optical absorption and fractal structure of adsorbate within a porous glass
Author(s):
Yuri L. Kolesnikov;
T. D. Kolesnikova;
A. V. Sechkarev
Show Abstract
Early it was discovered [1] that in course of impregnation of thin porous glass samples with organic dye molecules from solutions, an optical density decreases starting from certain stage despite of continuous character of the dye diffusion into glass. This effect may be interpreted as due to processes of space distribution of dye molecules within porous glass (PG), resulting in creation of fractal clusters. The purpose of present paper was the further detailed study of fractal properties of activated PG and the attempt to determine the fractal characteristics of molecular structures of the objects under investigation.
Phase-shifting interferometric data processing based on recurrence filtering methodology
Author(s):
Igor P. Gurov;
Adalet N. Djabiev
Show Abstract
Interferometric data in 2D phase-shifting interferometry (PSI) can be expressed as K samples of M-dimensional signal (MDS), where K-1 is the number of phase steps, M equals N X L is the single interference pattern points number. Whole quantity of PSI data can arrive at several Mbytes. It is not convenient for data processing in real time. We propose new Recurrence Phase-Shifting Interferometry (RPSI) technique. RPSI gives the optimal assessment of MDS phase on each point by the recurrence procedure of signal processing. It is predicted the signal value from previous step to next step. The prediction error is used for signal parameters correction with taking into account the particularities of signal model. It was discovered that true phase estimation in conventional one-wavelength interferometer is arrived by 8 - 11 phase steps that is in good agreement with known PSI methods. The advantages of RPSI technique are: noise- immunity, quickness of signal processing and moderate requirements to phase step accuracy.
Some results concerning the performance of quarter-wave Fresnel Birhomb
Author(s):
Constantin Ghita;
Lucsita Ghita;
Mariuca Gartner;
Gabriel Dumitru;
Dan G. Sporea
Show Abstract
Two Fresnel birhomb (lambda) /4 retarders have been realized from glass and fused quartz respectively, both having identical geometrical parameters but different residual stress birefringence of the raw material. Their behavior as achromatic retarders were examined in a null spectroscopic ellipsometer. The way in which the performances of this type of retarder depend on the residual stress birefringence is presented.
Relaation of photodarkening in SiO-As2S3 composite layers
Author(s):
Ivan Z. Indutnyi;
Peter E. Shepeliavii
Show Abstract
Investigated in this work is the reversible photostimulated red absorption edge shift (photodarkening), (Delta) Eg, of As2S3 nanoparticles embedded into the SiO matrix. As compared to continuous films, the remarkable (Delta) Eg increase (up to 4 times) with decreasing of As2S3 particle sizes was revealed. The exponential dependence of (Delta) Eg on storing time at different temperatures has been obtained. An activation energy of the transition of As2S3 nanoparticles structure from metastable, photoexposed state to ground, annealed state is equal 0.78 +/- 0.06 eV. The effects are related to a space confinement of the photoexcited carrier diffusion length and influence of particle sizes on the intermediate-range order scale structure relaxation in the As2S3 nanoparticles.
Reorientation of dye-doped liquid crystal under the action of circularly polarized light
Author(s):
Denis Andrienko;
Denis Fedorenko;
Yuri A. Reznikov
Show Abstract
We studied the effective interaction of the angular momentum of light with a liquid crystal (LC) doped with azo-dye. The experiments were carried out in a combined cell with one substrate providing strong unidirectional planar alignment of LC and the other covered by isotropic polymer layer providing a degenerated planar alignment. The effect manifests itself as azimuth reorientation of the liquid crystal director under the action of circularly polarized light in the absorption band of azo-dye. The new orientation of LC was captured by the command surface because of a light-induced alignment memory effect. To describe the experimental dependencies we solved the self-consistent problem of the propagation of a circularly polarized light in the absorbing nonlinear media using the geometric optics approximation. Comparing experimental data with numerical evaluation we obtain the basic parameters of the system: the orientation nonlinearly coefficient and the value of anchoring of the director with the polymer surface.
Laser depolarization in inhomogeneous media
Author(s):
Alexander G. Ushenko
Show Abstract
Wide application of lasers in the optic of scattering media has stimulated interest to wavefront transformation during light propagation in inhomogeneous media. The processes of depolarization laser field scattered by rough surface are investigated.
Optical peculiarities of thin absorbing films
Author(s):
Tamara A. Kudykina
Show Abstract
Optical parameters of thin semiconductor films in visible region are investigated with two different methods: use the new analogues of Fresnel's formulas for absorbing media for calculation of reflection and transmission and, use the calculation of an index of refraction on a base of a phase change on reflection. Results of these methods agree well. Thickness dependencies of n(d) and k(d) of Ge, Si, Se, Te were obtained for the experimental data. Curves n(d) have resonance maxima at thicknesses, which are less than light wavelength in a medium in (pi) times. Curves k(d) in this region have minima or even change their signs showing that both absorption and spontaneous emission of light take place. In the limit d yields 0, n(d) trends to unity.
Optical properties of hydrogenated amorphous carbon determined by ellipsometry
Author(s):
Margit Koos;
Tivadar Lohner;
Said H. Moustafa;
Istvan Pocsik
Show Abstract
The complex dielectric function [(epsilon) ((omega) ) equals (epsilon) 1((omega) ) + i(epsilon) 2((omega) )] and the complex refractive index [N((omega) ) equals n((omega) ) + ik((omega) )] are presented for diamond-like amorphous carbonlayers as well as for amorphous carbon thin films (a- C:H) exhibiting other properties. By employing spectral ellipsometry the optical constants were determined in the photon energy range of 1.47 - 4.59 eV. Series of thin films were prepared in radio frequency plasma discharge of methane by varying the negative self bias (US.b.) in the range of 200 V < US.b. < 600 V. The a-C:H samples in this series exhibit transition in electrical and optical properties with increasing room temperature conductivity from approximately 4 X 10-10 (Omega) -1 cm-1 to 2 X 10-2 (Omega) -1 cm-1 and with decreasing optical gap from 1.3 eV to 0.5 eV as the deposition voltage changes in the range of 200 - 600 eV. The most pronounced changes in optical constants and in bonding structure occur near 500 V self bias. The (epsilon) 2((omega) ) spectrum exhibits a broad maximum which shifts to lower energies by increasing deposition self bias. The optical properties are discussed in terms of electronic band structure related to sp3 and sp2 hybridized bonding states of carbon atoms and to intermediate range ordering of sp2 bonded sites.
New standard reference material set for UV spectrophotometer linearity test
Author(s):
Gyorgy Andor;
Gyula Dezsi
Show Abstract
The quality assurance system is based on accredited laboratories around the world. The instruments used for certified measurements are required to be traceable to national measurement institutes. The common solution for spectrophotometer linearity, stray light and wavelength calibration is a set of certified standard reference materials (SRM) made of absorbing glass. Unfortunately, in the UV spectral range neutral absorbing glass does not exist. There is a demand for commercially available SRM for linearity test in the UV. A new set of five evaporated metal on glass filters was developed in the density range of 0.2 - 3. This talk is about the spectral transmittance and spatial uniformity testing of the SRM set.
Theoretical and practical problems of the application of laser-induced plasma emission spectroscopy in geological prospecting
Author(s):
Laszlo Andrassy;
Bela Nemet;
Levente Vihar
Show Abstract
We examined the elemental distribution originating from the macro- and micro mineral structure of the core samples by two Laser-Induced Plasma Spectrometer (a time-integrated-- LIBS, and a time-resolved one-TRELIBS). We used randomized distribution of the measuring points on cut core samples and on pulverized homogenized ones. For plasma production were used low pulse energy (10 mJ) Q-switched Nd:YAG lasers. The probability frequency of the elements in the core sample was investigated with the help of distribution profiles. The principals of the quantitative evaluation and the calibration technology are also described.
Time-resolved optical monitoring of laser-produced plasma derived from carbon
Author(s):
Bela Nemet;
Ida Zs. Kozma
Show Abstract
Optical emission studies of neutral and fast ionization atomic forms, as well as C2 and CN molecules in plasma obtained by Nd:YAG laser ablation of graphite in atmospheric nitrogen. The Time-Resolved Laser-Induced Breakdown Spectroscopy was shown as a convenient technique for monitoring the evaluation of the components of the laser- produced plasma derived from carbon.
Optogalvanic effect in hollow cathode discharge for wavelength calibration of diode lasers in the visible
Author(s):
Sanka V. Gateva;
R. Djulgerova;
Ch. Andreeva;
Marian A. Taslakov;
Stefka Cartaleva
Show Abstract
Good signal-to-noise ratio optogalvanic effect (OGE) has been obtained in a hollow cathode discharge using commercially available low cost and low power diode lasers emitting in the visible region of the spectrum. The OG profiles of Ne and HE transitions suitable for diode laser wavelength locking to absolute reference have been studied. The amplitude and sign of the optogalvanic signal (OGS) have been measured simultaneously with the absorption in dependence on the laser power an the gas discharge parameters in order to find the conditions for optimum OGS.
Modular PC-controlled polarimetric ellipsometer with variable angle of incidence and spectral options
Author(s):
Tamas Mosoni;
P. Petrik;
Miklos Fried;
Istvan Barsony
Show Abstract
We have built a modular, PC controlled ellipsometer with variable angle of incidence measuring possibility. We used a HeNe laser, PIN-diode detector and film polarizer in the analyzer and polarizer elements at first. The analyzer, polarizer and goniometer unit of the ellipsometer are moved by a computer controlled mechanism. The data processing program developed by us makes it possible to evaluate measurements with several angles of incidence, too, which are used to measure samples with complex layer structure. The units of the equipment are easily replaceable in consequence of modularity. It has been developed further to a spectroscopic ellipsometer in the spectral range of 400 to 641 nm by using a xenon lamp and a CCD array detector with optical grating as a diffraction element in spite of a laser and a PIN-diode detector. The analyzer was rotated by a step-motor (quasi-stationary method) or a DC-motor (dynamic method). These two methods allow the choice of a faster but less accurate (dynamic method) or a slower but very precise (quasi-stationary) measurements. Further development of the quasi-stationary arrangement will provide a speed comparable with the dynamic method together with a high accuracy.
Fluorescence spectroscopy of bacteriorhodopsin at room temperature
Author(s):
Atanaska Andreeva;
Villen Kolev;
Tzvetana Lazarova
Show Abstract
The chromophore fluorescence of bacteriorhodopsin (BR) has been studied by using visible lines of an argon and He-Ne laser at room temperature. This fluorescence is extremely weak and appears as an unstructured band in the 650 - 880 nm range. The same line shape of the emission spectra of dark- and light-adapted BR recorded at low light excitation intensity implies that the emission of 13-cis conformation of retinal is not observable at these conditions. The analysis of the spectra recorded at different pH, intensity and wavelength of excitation light show that the spectrum of BR in fact contains at least three emission bands. They can be assigned to all-trans BR, O and Q intermediates, accumulated during the photocycle. As a most probable emission due to only all-trans BR in light-adapted membrane, we assign a band with a maximum located at 730 nm (13700 cm-1) and a full width of half maximum equals 2580 cm-1.
Switching of light by the use of optomechanical microdevices
Author(s):
Rolf Goering;
Steffen Gloeckner
Show Abstract
Fiber-optic switches become more and more appealing components not only in the field of optical communication, but also in measurement systems, sensors and data storage. We have developed a number of concepts for fiber optic switches, all based on different types of special microoptical components, actuated by miniaturized mechanical systems, primarily piezoelectric actuators. We present microoptical configurations and discuss their potential for the creation of different types of miniaturized switches.
Recent advances in diffractive- and micro-optics technology
Author(s):
G. Michael Morris
Show Abstract
Recent advances in single-point diamond turning and single- point laser pattern generation permit diffractive- and micro-optics components to be fabricated with optical performances approaching the theoretical limits. This improved quality is spurring active product development in a number new application areas, including head-mounted displays, laser printing systems, optical telecommunications, optical data storage, and laser projection systems.
Optical probe systems for miniature spectrometers
Author(s):
Ivan D. Nikolov
Show Abstract
The optical reflectance and absorbance dip probes operating with PC plug-in spectrometers are examined. A number of reflective optical systems have been designed. The achieved configurations are usable for UV, VIS and NIR spectral regions. The optical probe systems are fulfilled on the basis of one or two reflective components with one or two optical fibers. The applied optical materials and reflective layers are examined.
Telecentric/inverse-telecentric objective for optical data storage purposes
Author(s):
Gabor Erdei;
Gabor Szarvas;
Peter Kallo;
Emoeke Loerincz
Show Abstract
In most optical storage methods data bits are stored in the form of microscopic pixels on the surface of an appropriate storage material. Some currently developed techniques apply parallel data processing by multiple data bit access simultaneously. Such methods require special imaging systems for data recording and retrieval. In our laboratory a page- organized optical memory card reading/writing equipment is under development. According to the basic principle 256 by 256 data bits are processed at the same time, the corresponding pixels are arranged in a 2D array format. The same objective is used to image the selected data page both at writing in and reading out. This objective performs diffraction limited imaging in an extended field, it has low distortion, and it images each pixel of the same value with the same intensity. To achieve all these specifications a telecentric/inverse telecentric imaging system (a special type of afocal systems) offered a suitable solution. This paper describes the advantages of telecentric/inverse telecentric systems in optical imaging by detailed presentation of our objective. The discussion includes specification and design process of the objective together with our test results performed on the fabricated prototype.
Fringe contrast evaluation by means of histograms
Author(s):
Songcan Lai;
Gert von Bally
Show Abstract
The quality of interferograms is of the most concern in interferometric experiments. Present approaches to evaluate the contrast of interferograms are neither efficient to be carried out nor insensitive to noise. In this paper, we study the mean dynamic range and imbalance of grey levels on the basis of histograms. Analytical and calculation results show that these parameters are closely related to the contrast of interferograms. They are insensitive to noise disturbance and easy to be implemented with efficient computer algorithms and, therefore, can be used to estimate the quality of interferograms in real-time.
Rastered photothermoplastic carrier as a recording system for halfton imaging
Author(s):
Igor V. Ciapurin
Show Abstract
This paper studies the processes in photothermoplastic carrier, which lead to halftone image recording by preliminary formation of a raster surface relief. The methodology employed provides the necessary diffraction efficiency value in the illuminated areas of the photothermoplastic carrier as well as a low diffraction efficiency value in background areas. The results obtained can be used to design and to develop of microphotography systems for reprography applications.
Image description using Gabor wavelets
Author(s):
Dan Cojoc;
Paolo Grattoni;
R. Nerino;
Giuseppe Pettiti
Show Abstract
A technique for the detection of characteristic points and local description of an image is presented. This technique is based on the use of Gabor wavelets and allows point-to- point correspondence between two images of the same scene taken from different points of view. In order to evaluate its usefulness, the technique is compared with the classic local correlation approach.
Determination of the real performance for night vision systems
Author(s):
Marinica Mirzu
Show Abstract
The model for the detection of the images delivered by optoelectronical devices, developed by Rose on the base of fluctuation theory, establish the upper limit of their performance, it doesn't include the optical parameters, useful for a controlled optical design of the system components. The model presented take in account not only the degradation of the signal to noise ratio (S/N) on the photocathode but, in the same time, the noise of the amplification process in the image intensifier (noise factor) and the deterioration of the signal by the image formation optical components which are `low-pass' filters for spatial frequencies of the target. The final S/N is compared with the experimental determined S/N, required by the human eye to detect optoelectronical images, with a certain probability. The field experiments presented demonstrate the viability of the theoretical assumptions and relations. In this way, the optical design of this kind of devices may be conducted in a controlled way, without useless efforts and costs, with the certitude that the improved performances are obtained.
Imaging technology based on As38S62 thin layers
Author(s):
Alexander V. Stronski;
Miroslav Vlcek;
A. Sklenar
Show Abstract
The present paper is concerned with an investigation of the image formation properties of As38S62 thin layers and their application in the surface relief formation. The spectral dependence of the index of refraction n of variously treated samples (virgin, exposed, annealed) was obtained from optical transmission in the spectral region 0.4 - 2.5 micrometers . The energy dependencies of n for variously treated samples were well fitted by the Wemple-DiDomenico dispersion relationship and were used for the estimation of the single-oscillator model parameters. It was found, that exposure as well as annealing causes an increase in refractive index n values over the all spectral region. The values of optical dielectric constant (epsilon) is also increasing. Changes of the single-oscillator model parameters induced by exposure and/or by annealing are discussed on the basis of photo- and thermally induced structural changes, which were directly confirmed by Raman spectroscopy. Such photostructural changes provide good etching selectivity of As32S62 layers in amine based etching solutions. This provided possibility for the fabrication of surface-relief patterns, in particular, diffraction gratings. The results obtained, show that As38S62 inorganic resists can be successfully used in holography and other optical applications.19
Local dioptric power matrix and prismatic effects of spherical, aspherical, and spherotorical ophthalmic lenses
Author(s):
Jose Antonio Gomez-Pedrero;
Jose Alonso;
Eusebio Bernabeu
Show Abstract
We have computed the prismatic effects presented by several kinds of ophthalmic lenses: spherical, aspherical and spherotorical ones by means of the generalized expression of the Prentice's law. This expression use the local dioptric power matrix formalism (developed by us in previous works) in order to compute the prismatic deviation of the light rays along the surface of an ophthalmic lens made by arbitrary refracting surfaces with an acceptable degree of accuracy. This formalism allows the computation of prismatic powers without employing numerical ray tracing. We have compare the calculated prismatic effects with those obtained by means of numerical ray tracing finding a good agreement between them.
Hybrid plastic-glass optical systems
Author(s):
Ivan D. Nikolov;
Christo D. Ivanov
Show Abstract
The results obtained in the realization of a 3X magnifier hybrid optical system for NIR goggles are presented. A dispersive formula for optical plastics refractive indices computing is used. The configurations and residual aberrations of the designed system are discussed. The plastic-glass devices are more cheap and effective for a mass production of binoculars.
Mirror-lens optical system for image spectroscopy device
Author(s):
Ivan D. Nikolov;
Zornitca P. Zaharieva
Show Abstract
A Cassegrain type mirror-lens optical system for video- imaging spectrometry was designed. The optical performance is defined for a focal length of 500 mm, F-number no greater than F/5, a spectral region from 250 nm to 1050 nm and a linear image semi-field height of 15.37 mm. The residual aberrations are presented. The Cassegrainian objective assembly was examined under the requirements to provide a perfect image of the Earth surface stripe.
Application of optical design software in the analysis of "unknown" optical systems
Author(s):
Dunja Soldo Roudnicky
Show Abstract
Optical design software is not very usable in designing new optical systems only, but also in analysis of `unknown' systems. When measurements of radii of curvature, focal lengths and axial thickness of elements are done, we use SIGMA 2100 Optical design software (Kidger Optics). We determine which optical glass fits the nearest measured focal length of each element. We also get aberration curves of elements and the whole system. In such a way we analyze elements of an eyepiece which is the part of a compound panoramic sight. Since we now have all specifications of this eyepiece, it is possible to optimize glasses and radii to the more convenient ones, without a risk to change the performance of the whole optical system. This method gives us a possibility of reparation and adaptation of `unknown' optical systems with a high yield.
Specific problems of the optical scanning system optimization
Author(s):
Mee Suk Jung;
Won Don Joo;
Sergey A. Rodionov
Show Abstract
Some specific problems of the optimization of optical scanning system different from common optical system are investigated. We describe the optimization procedure which includes this specific requirements for a distortion, movement of scanning elements, and optimization function connected with energy concentration in beam spot which is not the image of source in common. Also, Kogelnik's ABCD law is used for scanning spot size determination.
Optical method for real-time position control in experimental equipment for local irradiation and system for precise and discrete local irradiation
Author(s):
Roxana N. Radvan;
Roxana Savastru;
Dan Savastru
Show Abstract
Complex up-graded equipment for visual analysis, measurement, positioning and intervention in microscopic field is described below. This system is not extremely automated because it have not obstructs the user's facilities and his possibility to operate immediately in the studied process. The high accurate system for positioning speculates the superior precision of the metrological criterions based on methods with symmetric framing. The present paper indicates just the final solution and mentioned some interesting remarks about the disadvantages of other tested solutions. This equipment is suitable for various studies of the effects of laser interaction in biological tissues and not only, in photolithography, laser cleaning, for different techniques of identification etc.
Pose estimation of an active stereo system by principal moments of point features
Author(s):
Dan Cojoc;
Paolo Grattoni;
Giuseppe Pettiti;
R. Nerino
Show Abstract
The estimation of the pose variation (egomotion) of a vision system while looking at the same scene from two different poses is both of theoretical and practical interest in computer vision. In this work we deal with this problem by developing a method to estimate the relative motion of our stereo vision system with respect to an object surface in a static scene. The images of the object taken from different views are described by a set of well localized 2D features named key points with associated local descriptors. These descriptors are based on coefficients of a Gabor wavelet transform of the images, and on the 3D object co-ordinates of the corresponding points in the space. 3D point co- ordinates are evaluated by means of a fixation process performed by our active stereo vision system. A selection process of key points based on the similarity of their descriptors in the two images produces two sets with the same number of key points, every set having a high probability to be composed by the correspondent points in the other images. The centroids and the principal moment axes (roto-translation invariants) of the 3D point co- ordinates of the two sets are evaluated, and the relative motion between the two poses is recovered from this information, thus avoiding a direct point to point matching.
Use of aberrations that arise during focusing of laser beam by spherical mirrors in laser processing
Author(s):
L. F. Golovko;
V. V. Roman
Show Abstract
The calculation method and mathematical model of focusing powerful laser beams by spherical mirrors process are proposed. The results of its theoretical and experimental study, regularity of intensity distribution changing, the form and cross-section size of beam depending on focusing condition, recommendation on application during laser processing of materials are adduced.
Economic microscopic image analysis/processing system
Author(s):
Laszlo Nanai;
Cs. Beleznai;
Ferenc Ignacz;
Vince Orova
Show Abstract
In the past years image analysis has gained great relevance in several fields of scientific application. With these systems an affordable price might be limiting factor for small-scale research projects or educational purposes. The system presented here provides an excellent performance- price ratio and is thus an excellent choice for low-budget applications. The system is described and its capabilities are demonstrated in a scientific example.
Novel concepts and technologies for manufacturing optical microdevices
Author(s):
Wolfgang Ehrfeld;
Hans-Dieter Bauer;
Dietrich Drews;
Manfred Lacher
Show Abstract
The development and fabrication of micro-optical devices are of increasing importance in the field of data- and telecommunication networks capable of transmitting multimedia signals with high bit rates. Miniature optical sensors such as spectrometers and interferometers are another example for rapidly growing markets with a wide range of applications in biotechnology, chemistry, pharmacy, environmental technology, and automation, to namely only the most obvious. Various technologies are used for the development and fabrication of such devices. However, the success of the resulting product heavily depends on its price. Therefore, the techniques for the manufacture of micro-optical devices are at least as important as the product itself. In this presentation fabrication concepts and technologies will be discussed. By fabrication we naturally mean more than the production of a master that allows mass-production of the product. Among the criteria are also the pros and cons of the material to be used, automated assembly aspects, the compatibility with existing components or systems etc.
Fabrication of reflection gratings by aluminum coating on holographic transmission gratings
Author(s):
Habib Madjidi-Zolbin;
Nasser Partovi Shabestari;
R. Sheibani
Show Abstract
The fabrication of holographic reflection gratings can be done either directly or by first making a phase transmission relief grating and then metallizing its surface by an appropriate metal. In this paper, the fabrication of reflection gratings with different spatial frequencies, from 100 L/mm to 1200 L/mm registered dissimetrically are reported and the curves of diffraction efficiency versus the slope angle are illustrated and finally the results are interpreted.
Microcomposition of optical materials based on nanoporous matrices
Author(s):
Vladimir I. Zemskii;
Yuri L. Kolesnikov;
Alexander F. Novikov
Show Abstract
The developments and researches results are reported concerning new optical media with required properties on the basis of sodium-borate-silicate nanoporous glasses (PG) which contain on its surface the physically sorbed metal- complexes and organic compositions. These media demonstrate the characteristics not achievable with use of preparative methods both for solid materials and for liquid solutions. First of all this concerns the organic dye molecules and metal-complexes immobilized on the surface of PG.
Blazed holographic diffraction grating fabrication using As2Se3 inorganic photoresist
Author(s):
Peter F. Romanenko;
M. V. Sopinski;
Ivan Z. Indutnyi
Show Abstract
The method of blazed holographic diffraction gratings fabricated by transformation of an original symmetric grating grooves into asymmetric ones using additional inclined irradiation by a monochromatic, or white light and repeated chemical etching have been developed. As photoresist material for gratings recording light-sensitive As2Se3 layers were used. Numerical modeling of the asymmetric groove formations was also carried out. The numerical results are in a good agreement with experimental groove profiles obtained by D3000 NanoScope. The asymmetry of produced gratings are clearly displayed in angular and spectral dependencies of the diffraction efficiency. The investigations shown that by changing the original grating formation parameters and the additional treatment conditions it is possible to produce blazed holographic gratings with designated groove form and blazed angle.
Fabrication and properties of light spiral filters
Author(s):
Miroslav Miler;
Ivo Aubrecht;
Ivo Koudela;
Jaroslav Wagner
Show Abstract
A simple technique of obtaining light spiral (helium) filters in UV exposed photoresist layers consisting in a combined use of binary masks and revolution of the photosensitive layers during exposition is presented. The filters investigated experimentally are inspected by observing intensity distribution in a laser beam reflected from the sample. The filter giving the angular phase shift variation which is close to that needed for the generation of the first order Bessel beam is realized.
High-quality low-loss coatings for diode-pumped solid state lasers
Author(s):
Elena A. Levchuk;
Vladimir V. Novopashin;
Alexander V. Shestakov
Show Abstract
The appearance of new types of lasers (for example, diode- pumped solid-state lasers) required development of the high quality low loss coatings for various spectral regions. These coatings can be divided into following groups: antireflective, high-reflective and cut-off filters. Various aspects of producing these coatings have been investigated. There are choice of the optimum construction of the optical coatings to obtain the required parameters in the specific spectral region, development of the production process to obtain the reproducing results when assembling lasers, study of optical parameters. All types of the optical coatings have been tested in the assembly of the lasers. Now these coatings are successfully used in the commercial lasers.
Dielectric interference coatings for medical examiner set up at 193 nm
Author(s):
Vladimir V. Novopashin;
Elena A. Levchuk;
Alexander V. Shestakov
Show Abstract
The results of obtaining and investigations coated optics in deep ultra violet (UV) at 193 nm are considered. For successful using in excimer lasers and medical systems the separate optical elements must provide either a good transmission for laser irradiation or enough high reflection. Numerical design and obtaining of UV dielectric coatings are strongly influenced by the material properties in this wavelength region. The peculiarities for thin films in this region are: a limiting factor of the evaporation materials, homogeneous of the film along the surface, and high laser strength. The interaction between excimer laser photons and optical coatings can be determined as two combined process of high repetition rates and high energy densities. These processes influence both on substrate and on film. In this connection the investigations of optical properties of oxides and fluoride films are observed. Besides some new aspects in investigation of pure substrates are obtained. All films were produced by electron-beam evaporation and ion-beam influence was analyzed as variation of optical absorption and laser damage threshold of coated optics.
Near-field optics: force and torque
Author(s):
Soo Chang;
Sang-Soo Lee
Show Abstract
Optical force and torque acting on a small particle in the near zone of ultra-small structures illuminated with electromagnetic waves are analyzed and their application is discussed.
Laser resonators with Bessel-Gauss modes: design and analysis
Author(s):
Pertti Paeaekkoenen;
Jari Pekka Turunen
Show Abstract
Aspheric-mirror laser resonators are designed, which support Bessel-Gauss modes of arbitrary order. Conventional Gaussian-beam and Fabry-Perot resonators are obtained in the appropriate limits of pure Gaussian and Bessel mode. High modal discrimination is demonstrated numerically with the Fox-Li algorithm, and practical realization of Bessel-Gauss beams in resonators is addressed.
Suppression of spatial nonuniformity and nonlinearity in phase modulation in phase-shifting interferometry
Author(s):
Kenichi Hibino
Show Abstract
In phase shifting interferometers, spatial non-uniformity of the phase modulation often happens in such cases where as aspherical (or spherical) mirror is compared to the corresponding aspherical standard surface which is translated along the optical axis by piezo electric transducer to introduce phase modulation. The amount of phase shift is then different across the observing aperture depending on the gradient of the testing surface. The nonlinear sensitivity of the phase modulator causes a significant errors in measured phase when there is a spatial nonuniformity in phase shift. Many phase measuring algorithms reported to date cannot compensate for the spatial nonuniformity if there is a nonlinear phase shift. It is shown that if we add a new symmetry to the sampling functions of the phase measuring algorithm we can suppress the phase errors caused by the spatial non-uniformity of the phase shift. The new algorithms need at least one more image frame to acquire the symmetry. The lowest-order algorithm compensating for quadratic spatially non-uniform phase modulation consists of six frames.
Reflection and transmission of femtosecond pulses
Author(s):
Mihaly G. Benedict
Show Abstract
Instead of using a frequency dependent refractive index, we propose an alternative method to describe reflection and transmission of femtosecond pulses at the boundary of a new medium. It is a time dependent perturbation treatment of the problem, that follows explicitly the evolution of an ultrashort pulse passing through the boundary. The reflection and transmission properties depend on the relation between the pulse length and the relaxation time of the material.
Nonperturbative theory of cavity-controlled spontaneous emission of two-level atom trapped in two crossed cavities
Author(s):
Vladislav F. Cheltsov
Show Abstract
The time-dependent spontaneous emission spectral line shape of two level motionless atom placed in common antinode of two symmetrically detuned lossless modes has been investigated nonperturbatively. The line shape and its temporal evolution have been found to be a function of modes detuning and natural line width of isolated atom. The spectrum varies between singlet and triplet taking on the well-known Lorentz-shape form when detuning and natural line width become much larger than the coupling constant of interaction of the atom with modes.
Analysis of light interaction with a moving dielectric with applications to acceleration sensing
Author(s):
Maria Herminia Marcal;
Manuel Jose de Abreu Faro
Show Abstract
A general, systematic formalism is presented for obtaining the transit time of a light signal propagation in an arbitrarily moving dielectric medium along a given trajectory. The analysis is carried on an arbitrary reference system, not necessarily the rest frame of the medium. The explicit form of the transit time can be used to analyze the potentialities of various interferometric devices. In particular, a linear acceleration sensing device is investigated.
Two methods (numerical and analytical) of the analysis of complex moving waveguides
Author(s):
M. M. Shabat;
M. A. Abdel-Naby;
Y. S. Madi;
Dieter Jaeger
Show Abstract
This paper presents two methods of analysis of the complex moving waveguide. One approach is a numerical technique based on Davidenko's method, the other is a perturbation method. It is clear that if one wants to obtain more accurate results over a wide range it is necessary to develop numerical techniques capable for solving lossy waveguides that has a complex propagation constant or a complex dielectric constant. Newton's method is one of these methods which requires several iterations in the complex plane, but this method fails in most cases in producing satisfactory results. Davidenko technique offers an alternative which is efficient and reliable and which relaxes the extent of the restriction placed on initial guess to be sufficiently close to the solution. The main idea of Davidenko's algorithm is to reduce Newton's method for the numerical solution of n-coupled nonlinear algebraic equations into n-coupled first-order differential equations in a dummy variable. The second one is a simple and accurate perturbation method, where the real part (beta) ' of the complex modal index (beta) equals (beta) ' + i(beta) '' is obtained by solving the corresponding real eigenvalue equation and the imaginary part (beta) '' is given by ((partial)(beta) '/(partial)(epsilon) ')(epsilon) '', where (epsilon) equals (epsilon) ' + i(epsilon) '' is the dielectric constant of the absorptive layer, and ((partial)(beta) '/(partial)(epsilon) ') is obtained by numerical differentiation. Numerical results by Davidenko's method are compared with these obtained from the perturbation method. It is found that the perturbation method is in a good agreement with the numerical one. Furthermore, for the first time in our knowledge, the complex propagation characteristics are presented for moving waveguides. These results could be used in designing many optical moving sensors.
Talbot's bands
Author(s):
Zsolt Benko;
Margit Hilbert;
Zsolt Bor
Show Abstract
A new approach is introduced for the explanation of the formation of Talbot's bands by using the model of tilted pulse fronts. Numerical computations of this model are also given. An other interpretation of Talbot's original publication is also presented and explained. Simple experiments have been used to examine cautiously the dependence of the visibility of Talbot's bands on various properties of the plate: thickness, refractive index, dispersion. An experiment has been carried out to check the other interpretation, too.
Luminescent properties of organic compounds in nanodimensional aluminium oxide structures
Author(s):
A. Kukhto;
Eduard E. Kolesnik;
Alexander V. Mozalev;
Mohammad I. Taoubi
Show Abstract
Dielectric anodic oxide alumina films have a nanoscale 2D structure consisting of cylindrical pores placed perpendicularly to the surface. Such films with a regular structure where pores distance is equal to pore diameter and can be changed from 5 nm to 400 nm are created. The spectral and luminescent properties of different organic compounds luminescing in a wide spectral region included into the pores were studied. The photonic pseudo band gap have been established for both transmission and reflection spectra.
Thermo-optic bistability in an anisotropic multilayer interference filter
Author(s):
Georgy Zartov;
Krassimir P. Panajotov;
Tihomir Tenev;
Rumiana Peyeva
Show Abstract
In this work we investigate the behavior of anisotropic multilayer structures. A coupled thermo-optic multilayer model is used to simulate the static and the dynamical intensity and polarization response of interference filter with an anisotropic central layer of LiNbO3. Bringing the electro-optic and the thermo-optic properties together leads to new possibilities for controlling the bistable behavior of such a structure. It has been shown numerically that the longitudinal dependence of the temperature distribution can not be neglected for multilayer structure in general. We show that the thermo-optic response of an anisotropic resonator gives rise to both intensity and polarization bistable loops. The quantitative comparison of the simulations with the experimental data confirms the necessity of considering the 3D temperature distribution inside the filter. Our numerical predictions are compared with the experimental results, showing a very good agreement. The obtained results open new perspectives for further investigation and optimization of anisotropic interference filters, focusing on the interesting phenomenon of polarization driven optical bistability. Besides, the model can be used in the thermal engineering for many other active multilayer devices, where the thermal effects can not be neglected.
Effect of permeability on guided modes in planar structures
Author(s):
Kamil Postava;
Jaromir Pistora;
Petr Hlubina
Show Abstract
The study of guided modes in planar systems allows a precise characterization of refractive index, thickness and optical anisotropy. On the basis of the matrix elements, the conditions for waveguiding in magneto-optical simple layers, double layers and in sandwiches at transversal geometry have been specified. In this case there are two independent dispersion relations for TE and TM modes for discussed thin film configurations. Usually we assume that the relative permeability is equal to 1 in the frame of optical frequencies. This approximation is problematic in far infrared region or for ultrathin films in the optical one. Through the extension of the Yeh's formalism to magneto optical media the formulae of dispersion relations for guided modes in planar structures with both permittivity and permeability tensors have been derived. The permeability tensor effect at transversal magnetization on waveguiding in mono- and double layer systems and in sandwiches is analyzed in detail. The experimental possibilities of dark mode spectroscopy in the analysis of the planar magneto-optical systems inclusive of permeability tensor element specification are studied.
Helicity dependence of moire fringes formed by a helical grating
Author(s):
Keun Cheol Yuk;
H. B. Lee;
Jae Heung Jo;
Soo Chang
Show Abstract
We theoretically and experimentally investigate the properties of moire fringes formed by a helical grating illuminated with a white light source, we propose a simple moire method of determining the helicity state and the pitch in a helical winding of wire.
Computer simulation of coherent radiation scattering by highly anisotropic objects
Author(s):
Alexander A. Zinchik;
Sergey C. Stafeev;
Boris A. Fedorov;
Galina C. Elyashevich;
Alexander G. Kozlov
Show Abstract
The computer simulation results are reported for coherent light scattering by a microporous polyethylene film membrane. As an object for the analysis a SEM photographic picture of the membrane was used. For simulation, a calculation algorithm of a 2D Fast Fourier Transform was used. The binary approximation as well as amplitude and phase-amplitude approximations of the transmission function were taken. The obtained results were compared with the scattering pictures taken by means of a CCD-camera from the same membrane. The simulation results were found to be in a good agreement with the actual structure of the microporous film.
Numerical simulation of monochromatic light scattering on stratified surfaces
Author(s):
Victor I. Malyugin;
Michael Ya. Litvak
Show Abstract
The integral polygaussian model of random processes is employed for simulation of stratified roughness formed by secondary abrasive finishing treatment or wear of an initially rough normal surface. Examples of simulated profiles and dependencies of surface non-gaussian statistical parameters on the type and stage of the treatment are presented. Numerical analysis of scattering of a monochromatic gaussian beam based on the thin phase screen approximation demonstrates that non-gaussian features of the surface lead the strong specular peak due to the scattering from the upper smooth surface strata manifesting at the very beginning of the treatment and dominating over the diffuse scattering during all the process of the surface modification. The diffuse scattering radiation for stratified surfaces is strongly concentrated in the near- specular direction. The results of the investigation shows that traditional methods of normal surface roughness estimation based on the magnitude of the specular component of the scattering and the form of the diffuse indicatrice may result in misinterpretation when applied to the stratified surface.
Decomposition of a coherent light field using a phase Zernike filter
Author(s):
Svetlana N. Khonina;
Victor V. Kotlyar;
Victor A. Soifer;
Yixin Wang;
Dazun Zhao
Show Abstract
Aberration of the coherent wavefront are analyzed using a phase Zernike filter. Developed iterative methods allow us to design a filter that decomposes the analyzed light field into a set of diffraction orders with amplitudes proportional to the circular Zernike polynomials. Operation of a 25-channel filter is simulated.
Development and spectral characteristics of new scintillation materials based on oxide crystals
Author(s):
Mykola U. Bilyi;
S. G. Nedel'ko;
Yu. A. Hizhnyi
Show Abstract
Scintillation crystals as components of scintillation detectors are widely used in modern science and technique, especially, in medicine and high energy physics. High density of scintillation material is one of the basic requirements for creating of effective detecting devices. This advantage is incident to oxide crystals, that possess low radiation length and high atomic weight. Therefore such substances as bismuth germanate, yttrium silicate, bivalent metals tungstates, and others became an object of intensive investigations, especially seeing the elaboration of large calorimetric devices for elementary particles accelerators. The analysis of scintillation properties of various scintillator types showed that oxide materials, being at disadvantage in relation to traditional alkali-halide crystal systems in some scintillation parameters, excel them in rapidity, radiation hardness, chemical and thermal stability and operate successfully under conditions of strong irradiation, high temperatures, chemically active environment, mechanical stress, etc.
Ways and frontiers of fractal optics
Author(s):
Oleg V. Angelsky;
Peter P. Maksimyak;
Peter V. Polyanskii;
Vladimir P. Ryabukho;
Claude Aime
Show Abstract
The present-day state of fractalometry and fractalography is considered. Fractalographic techniques based on referenceless holograms and off-axis quadric holograms are introduced. The original technique for measurement of a chaos correlation dimension at the field is proposed as well as possibilities provided by implementation of this technique.
Diagnostic of asymmetrical fractals structure
Author(s):
Oleg V. Angelsky;
Alexander V. Kovalchuk;
Peter P. Maksimyak
Show Abstract
Diffraction of radiation by asymmetric Cantor fractals and diffraction gratings is studied. Asymmetry parameters of an object and its diffraction field are compared. It has been shown that the asymmetry coefficient of optical fields diffracted by the asymmetric fractals arises to be acceptable for evaluation of the asymmetry degree of the studied fractals. As empirical relations among fractal level, asymmetry of the object fractals, and coefficients of asymmetry of the field diffracted on them have been obtained.
Off-axis quadric fractalogram
Author(s):
Alexei V. Konovchuk
Show Abstract
Original holographic technique for self-imaging of a fractal-containing optical signal is introduced and demonstrated. The technique is based on off-axis far-field quadric hologram, i.e., a hologram whose amplitude transmittance contains the terms of power series expansion on exposure degrees up to the quadratic one. Being read out with the stored memory or its partial version, such a hologram reconstructs the conjugate image at the minus- second diffraction order. The complex-conjugated associative response is shown to be free of brightness disbalance among its different parts exhibiting in such a manner error- correcting properties. Besides, the fractality inherent the stored signal is enhanced at this associative response due to predominant phase conjugation of the edge diffraction wave.
Diffraction effects, scattering effects, analytical problems, numerical algorithms, and program packages
Author(s):
Milesa Z. Sreckovic;
S. Ostojic;
J. Mircevski;
Nenad K. Bundaleski
Show Abstract
Diffraction problems in analytical treatments and numeric have been constant topics for a very long time and there are a lot of different analytical expressions as well as numerical algorithms. The modern approaches are concentrated in the area of particle sizing, fiber optical sizing and loss evaluation in laser physics and techniques. Some problems between the fiber optics dimensioning and particles of cylindrical shape dimensioning are chosen and based on literature; some ameliorations in numerical approaches are made. The evolved expressions can be used for different laser wavelengths, different dimensions of disturbance objects (in scattering and diffraction phenomena) as well as different indices of refractions where the particles (in a very general way) are stratified. Some existing programs for scattering are discussed and the new computer architecture is presented here.
Reshaping of the spectrally resolved white-light fringes caused by dispersion
Author(s):
Attila P. Kovacs;
Zsolt Bor;
Robert Szipocs
Show Abstract
The shape of the spectrally resolved white-light interference fringes has been investigated theoretically and experimentally, when one mirror of the Michelson interferometer is a dispersive multilayer mirror and the other mirror is tilted. An analytical expression is found, which relates the shape of the interference fringes to the phase derivatives characterizing the dispersion of the multilayer mirror.
Variation of the read-out signal in an optical disk system with a centrally obstructed pupil
Author(s):
Seong Jong Park;
Sang Hyun Sim;
Chang Sub Chung
Show Abstract
We investigated numerically the variation of the read-out signal in an optical disc system having centrally observed pupil. Considered factors were the radius of central obstruction varied from 0 to 0.9 and the bump shape varied from rectangular bump to conic bump and the spherical aberration varied from 0 to 1 (lambda) . Based on the numerical calculation using scalar diffraction theory, we are able to determine the best central obstruction and the best bump shape and size giving the maximum value of read- out signal. We applied these results to real optical disc system like a commercial digital video disc system. These works can be facilitated the fabrication of real high density optical systems.
Determination of hiding power of paints by the Monte-Carlo method
Author(s):
Oleg N. Kozakov
Show Abstract
Simulation of paint's reflectivity by applying the Monte- Carlo technique has been performed. The necessary for simulation probability characteristics have been estimated from known paint's optical parameters, such extinction, single scattering albedo, scattering indicatrix of the elementar volume, reflection indicatrix of a substrate and optical thickness of the layer. The contrast coefficient and hiding power of a paint have been found from calculation of a diffuse reflectivity of the layers at black - RB and white - RW substrates. The computation has been performed for a paint with the following optical constants: pigment - np equals 2.53, (chi) p equals 2 (DOT) 10-2, and binder - nb equals 1.56, (chi) b equals 4 (DOT) 10-5. The developed technique may be applied to prediction of hiding power in various paints.
Results of excimer-laser-performed photorefractive keratectomy operations
Author(s):
Istvan E. Ferincz;
Imola Ratkay-Traub;
Maria Dinnyes
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We have performed excimer laser photorefractive keratectomy operations with a Schwind Keratom 2F to correct near- sightedness. 613 eyes of 348 patients were treated by this ablation method. We have selected 318 case, where the follow-up was at least 6 months long. The intended corrections were in the range of -1.75 D to -9.0 D for myopia. The optical zones were 5.5 and 6.0 mm. We present various results of the treatments: change of visual acuity, residual spherical refractive error, time valuation of healing, and ablation speed. We have found that the ablation speed of human cornea is depends on the age of patients. An equation is also presented to describe the relation between age and ablation speed.
Micro-optical fiber-tip components based on laser technology and their application in medicine
Author(s):
Vadim P. Veiko;
S. V. Kukhtin;
M. P. Tokarev;
Vladimir A. Chuiko;
D. G. Agapov;
K. Stolbovsky;
Alexey J. Nevorotin
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Geometry of laser light distribution within a target to be lased is considered to be crucial in laser medicine. If laser energy is transmitted via fiberoptic, then either bare, sculptured, lens, or mirror-based systems have been developed by many authors dependent on the specific application 2,8 A key problem of fabricating of a fiberoptic applicator [PA], however, is technology that could reproducibly provide a user with a needed model of FA. In particular, a few species of disposable FAs would be desirable, with different patterns of laser light distribution as related to a target. In the present paper, CO2 laser assisted technology is proposed that permits one to sculpture a PA in a way providing a geometry pattern required for a given procedure. Preliminary results of the study have been published elsewhere.
Some applications of optical fibers in medicine and disturbances in biomedical area
Author(s):
Milesa Z. Sreckovic;
S. Pantelic;
A. Marinovic;
Z. Tomic;
D. Nikolic;
S. Travica;
P. Uskokovic;
R. Aleksic
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The development of medical equipment, telecommunications and computer's technology provides new possibilities for diagnostic purposes. Usually, it is necessary to use optical image or noise transmission. The application of the medical system with a system of optical fibers determines specific requirements of parameters and characteristics given in this paper. The optical fiber as a medium has some limits, versus energy and a quantity of information which could be propagated and distortionless detected and demodulated. Therefore, the fiber systems in different fibers dispositions are relay in various applications schemes. In the first approximations (very often in many cases of applications) the fiber transmits the optical signal (the part of optical image) without affecting signals in other fibers. In that application, the placement of each fiber in the system must be well defined (equal on both ends). A large number of fibers (about 10000) are needed for coherent systems with high resolution. The quality of transmission depends on possible damages in the system and attenuation of each fiber. One of the devices for optical transmission, frequently used in medical diagnostics, is endoscope.
