We have grown high quality oriented nano particles of zinc selenide (ZnSe) on patterned gallium arsenide (GaAs) substrates. We have developed and used silver and gold based templates with domains of 35 μm. We observed that the films grew epitaxially on the non-patterned portion of GaAs wafers with 4° miscut from (001). Several samples of thickness ranging from 5 μm to 1 mm thickness of ZnSe were grown in a vertical closed tube using the temperature gradient as the driving force. The quality of the samples was analyzed by X-ray and morphology was studied by SEM, FIB, and AFM and by etching the films. The rocking curve showed that the FWHM values for different films were in the range of 300-350 arcs second. We observed that film on (001) portion of the template grew with smooth morphology but morphology was slightly different on the templates. The grown film had strong (111) peak also on the patterned substrate in addition to the (001) peak observed for the film on unpatterned substrate.

A study of the acousto-optic (AO) effect in a family of oxide crystals (including e.g., TiO₂, ZnO, LiNbO₃, and ferroelectric perovskites) as well as semiconductors has been conducted by finite element analysis method. In addition, the acousto-optic figure of merit (FOM) as a function of material's refractive index, density, effective AO coefficient and the velocity of the acoustic wave in the material, is also investigated. By examining the directional dependent velocity, acousto-optic coefficients, and refractive index, the acousto-optic FOM can be calculated and plotted in all directions revealing the optimal crystal orientation to maximize coupling between the optical and acoustic waves. A finite element model was developed to corroborate the predicted interaction. The model examines the diffraction that occurs by the optical wave as it travels through an acousto-optic medium. The combined information gained from Mathematica and COMSOL Multiphysics-based modeling is shown to be an effective means of predicating acousto-optic device functionality.

We present an experimental characterization of a fiber laser composed by an Yb-doped fiber spliced with a birrefringent photonic crystal fiber and a mechanically-induced long-period grating (LPG) into the laser cavity. According to the torsion properties of the LPG induced in the photonic crystal fiber, the Yb-doped fiber laser can be highly sensitive to twist and it can shown novel properties in its laser emission. Also, we show the splitting of attenuation bands of a longperiod fiber grating induced mechanically in different twisted photonic crystal fibers with high birefringence and their applications on the performance of tunable and switchable multiwavelength double-clad Ytterbium-doped fiber lasers.

We compare self-focusing of laser beam with Gaussian, super-Gaussian and ring profile in a medium with quadratic nonlinear response due to cascading SHG. The duration of the light pulse under consideration is about microsecond. Nevertheless, the dispersion of group velocity is also taken into account. We demonstrate a possibility of strong growth for intensity of the laser radiation without changing the pulse shape and Gaussian profile of the beam. For initial super- Gaussian and ring profile the Gaussian profile appears due to the diffraction of laser beam at certain section of nonlinear medium. Then, the optical radiation undergoes self-focusing without changing the Gaussian intensity distribution till appearance of the first nonlinear focus. This phenomenon has various practical applications. For example, it can be used for developing the laser system in microsecond range of pulse duration which operates in the regime similar to KLM regime for femtosecond laser system.

We investigated recording of holographic volume and surface-relief gratings in photorefractive crystal and in a photo-thermoplastic (PTP) holographic camera. Holographic recording with an image-bearing signal beam leads to the appearance of two Bragg and two or more non-Bragg diffracted beams that shows the transformed images in each beam (rotation and angular amplification of images). Using this real-time mode of interferometry, the hologram is retrieved with a deformed object beam, resulting in the appearance of fringes with a proper phase shift in each of four diffracted beams. Retrieval with a time-modulated single-pixel object beam lead of time-modulated response in all diffraction orders. This one-shot (one-exposure) phase-shifting interferometry results in clarifying the object wave-front information (as an example, from the surface deformation) and solving the sign ambiguity problem. This procedure demonstrates that high-resolution holographic imaging of the PTP holographic camera static deformations in the order of ~0.1mm can be revealed on the diffusion reflection surface. In addition, it was demonstrated, that using the PTP materials could achieve holographic recording and imaging through phase aberration, with the image appearing in the non-Bragg diffraction order.

Fiber Bragg gratings (FBGs) embedded in conventional fibers may serve as temperature sensors over a wide temperature range and withstand temperatures around 1200 K. A variety of linearly polarized (LP) modes for the wavelengths between 400 and 700 nm may be sustained in fibers with and without FBGs. The composition of the LP modes and their competition is instrumental for understanding physics of thermo-optics and thermal expansion effects in silica-based fibers. The first objective of this work was to model mathematically the competition between LP modes and modal distribution using the solutions of Bessel equations for the fibers with and without the gratings. Computer generated modes were constructed and the cut-off V-numbers (and Eigen values W and U) were determined. Theoretical results then were compared with experimental observations of LP modes for two separate ranges of temperatures: 77– 300 K and 300-1200 K. To study the formation of LP modes over the first temperature range, liquid nitrogen was used to cool down the fiber and a thermocouple was used to monitor the temperature of the fiber. Real time recording of the modal structure was performed using digital imaging and data acquisition instrumentation. To study LP modes between 300– 1200 K, the fibers were inserted into a tube furnace with temperature control. The wavelength of the infrared radiation was reflected by a FBG and detected by an optical spectrum analyzer. Radiation at the visible wavelength propagated through the fibers, and transmitted visible light was collected, analyzed and recorded with a CCD camera to monitor distribution of the LP modes in the samples with and without the FBGs.

A transmission type of collinear holographic data storage system (CHDS) based on photorefractive LiNbO₃ crystal is constructed. The polarization states of the coherent beams in the crystal are optimized for a larger dynamic range based on the coupled mode theory and the linearized band transport model of photorefractive effect. The optimization predicts that the photorefractive crystal will have a larger dynamic range by use of extraordinary light than using ordinary light for CHDS system when the grating wave vector is parallel to the c-axis of the crystal. It also predicts that the dynamic range for CHDS can be larger than that for traditional 90 degree holographic recording geometry. In the experimental results, data pages are recorded with the shifting multiplexing method in the LiNbO₃ crystal by using the extraordinary light.

The prism-based electro-optic beam deflector is a well-known technology dating back several decades. The primary factor that has inhibited its wide-spread application is the need for high control voltages - typically around 1,000V per degree of scanning for a device fabricated in bulk lithium niobate. We have used crystal ion slicing of lithium niobate to realize a beam deflector with an order-of-magnitude higher deflection sensitivity. We have demonstrated 1x5 switching of near-infrared light with a voltage swing of only +/-75V. While the optimal design of bulk deflectors is well established, the thin-film geometry requires careful consideration of the crucial factors of light coupling efficiency and control of beam divergence. This paper will discuss design issues for integrated 1xN switches based on this technology and their application to implementing a practical true time delay module for phased array systems.

The transfer matrix method (TMM) has been used to analyze plane wave and beam propagation through linear photonic bandgap structures. Here, we apply TMM to determine the exact spatial behavior of TE and TM waves in periodic refractive index structures of arbitrary thickness. First, we extend the TMM approach to analyze plane wave propagation through Kerr type nonlinear media. Secondly, we analyze second harmonic fields in a 1D nonlinear photonic crystal for arbitrary angle of incidence of the fundamental plane wave. This allows us to construct the overall transfer matrix of nonlinear waves for the whole nonlinear optical structure from all the individual layer transfer matrices. We extend this method to analyze the effect of second order nonlinearity to beam propagation by applying TMM to the angular spectral components of the beam(s).

On the base of computer simulation we found out the 2D soliton appearance after interaction of the Bose-Einstein condensate (BEC) with an obstacle (external potential). The number of soliton is defined by the velocity of motion of the obstacle and its spatial sizes as well as strength of the obstacle. The soliton of the BEC wave appears both for transmission wave and for the reflection wave also. Soliton appears for positive and negative (maybe, for chosen obstacle) value of the nonlinearity. The reflection of the BEC from the obstacle leads to a new mehcanism of the obstacle rounding. To prove the existence of the solition we construct the analytical soliton for the considering problem after both BEC propagation of the obstacle or its reflection from the obstacle.

A device converting cylindrical waves to plane waves is demonstrated. This device is comprised of two Luneburg lenses and Bragg gratings. The two Luneburg lenses are placed in contact with each other and Bragg grating is placed perpendicular to the longitudinal axis of the lenses. The function of the Luneburg lens is to convert cylindrical waves to plane waves and vice versa. The function of the Bragg grating is to reflect the plane waves. If we put the cylindrical wave source on the contact point of the lenses, short range plane waves are generated. We verified them by using the FEM simulations. Efficiency of the device is also analyzed depending on wavelength and dimension of the lens.

In this paper, we have reviewed our recent works on IR supercontinuum generation (SCG) and its applications. First, we provide a brief review on the physical mechanism of the supercontinuum generation and our previous works in this field. Second, a thinner IR crystal fiber is fabricated. The supercontinuum generation in this thinner fiber is also demonstrated, which shows the enhanced performance. The suggestion for the future effort is also included.

The study reveals an innovative design of the optical waveguide based on potassium tantalate niobate (KTN) crystal. The device’s guiding properties, which benefits from the large electro-optic coefficients of KTN crystal, can be dynamically controlled by an external electric field in a relatively simple waveguide structure. Finite Element Method (FEM) and Beam Propagation Method (FEM) are used in the theoretical part of this work which shows that the KTN based dynamic waveguide has good potential on applications of several kinds of optical switches and modulators.

In this paper, we investigate the application of the EMD to automatically reduce speckles on the fringe pattern. It is found that the number of the removed intrinsic mode functions (IMFs) is sensitive to the period of the fringe pattern, but not sensitive to the speckle size and the speckle amplitude. Thus, a database system based on statistic simulations for finding the optimization of removing speckles is built. With this database, more than 80% speckles on the fringe pattern can be robotically reduced.

Low threshold and widely tunable InAs/InGaAs/GaAs quantum-dot external-cavity lasers are implemented with gratingcoupled Littrow configuration. Throughout the tuning range of 130 nm, from 1160 to 1290 nm, the threshold current density is less than 0.9 kA/cm² and without noticeable threshold jump. For a shorter-cavity device, the injection current is kept at a record low value of 90 mA but the tuning range is further extended from 1143 to 1293 nm. We discuss the effect of cavity length on the tuning characteristics and propose the strategy for design and optimization of multilayer quantum-dot structure.

Nonlinear multi-photon laser wave mixing is presented as an ultrasensitive optical detection method for chem/bio agents in thin films and gas- and liquid-phase samples. Laser wave mixing is an unusually sensitive optical absorption-based detection method that offers significant inherent advantages including excellent sensitivity, small sample requirements, short optical path lengths, high spatial resolution, high spectral resolution and standoff remote detection capability. Wave mixing can detect trace amounts of chemicals even when using micrometer-thin samples, and hence, it can be conveniently interfaced to fibers, microarrays, microfluidic systems, lab-on-a-chip, capillary electrophoresis and other capillary- or fiber-based chemical separation systems. The wave-mixing signal is generated instantaneously as the two input laser beams intersect inside the analyte of interest. Laser excitation wavelengths can be tuned to detect multiple chemicals in their native form since wave mixing can detect both fluorescing and non-fluorescing samples at parts-pertrillion or better detection sensitivity levels. The wave-mixing signal is a laser-like coherent beam, and hence, it allows reliable and effective remote sensing of chemicals. Sensitive wave-mixing detectors offer many potential applications including sensitive detection of biomarkers, early detection of diseases, sensitive monitoring of environmental samples, and reliable detection of hazardous chem/bio agents with a standoff detection capability.

Noise from optical and electronic components of a fiber optic gas sensor system using wavelength modulation of the DFB laser diode in either transmission or reflection mode were investigated. Our experimental results indicate that reflective type cells give poorer performance due to interference effects from connectors and joints within the fiber system compare to transmissive type cell. Intensity noise from optical coupler, collimator, was measured and its affection to sensing system was discussed. In order to raise the signal to noise ratio (SNR), signal processing methods, such as data average, low pass filter were used and compared. The results would be a useful engineering tool to design high SNR optical gas sensing system.

We present results based on theoretical analysis on how fiber sources doped with Er³+ and Er³+/Yb³+ operate in the amplified spontaneous emission (ASE) regime. Results of the model such as pump response, output in the forward and backward directions along the length of the fiber and output efficiency are presented. After more development, these sources could be used in DWDM systems to generate a number of signals around the 1550nm window.

A periodic parallel microgrooves on the silicon substrate with 2.5 um spacing covered by various nanostructures can be fabricated by using the interfered femtosecond laser illumination. The morphology created by this approach is apparently different from the common method using the femtosecond laser and sulfur hexafluoride (SF6). However, the treated silicon area could tremendously reduce the reflection from the surface. The reflectance of the structured surface is around 5% throughout the visible to near IR (1.1 um) despite of the viewing angle, which is comparative. Furthermore, the effect of the reflectance reduction is weaker but still obvious when wavelength is beyond 1.1 um, which is believed to be able to extend to the mid IR range.

In this paper, the fabrication of high aspect ratio 3-dimensional titania (TiO₂) nanostructures based on costeffectively hydrothermal synthesis method is presented. A novel patterning method to overcome the tradeoff between tall trunks (nanorods) and large spacing is addressed. Polydimethylsiloxane (PDMS) was adopted to restrain the growth of the trunks (nanorods) of nanoforests to well control the morphology and surface area of TiO₂ nanoforests.

In this paper, the radiation induced air fluorescence is investigated for several different types of radiation sources, including high brightness laser sources, X-ray radiation sources, and alpha radiation sources. First, the air fluorescence spectrum with three spectral bandpass filters induced by the high intensity laser was analyzed from spectrometer detector. Second, the air fluorescence intensity induced by different types of radiation are measured from photomultiplier tube detector and followed by discussion. Finally, the potential application of radiation induced air fluorescence for the radiation detection is addressed.

Slow light plays an important role in the fields of all-optical signal processing and integration photonics. It has shown many potential applications, such as realizing optical delay lines or buffers, enhancing linear and nonlinear light-matter interactions, as well as increasing the sensitivity of the interferometers and transducers. In this paper, hollow-core photonic bandgap fibers made from high index glasses are designed by infiltrating microfluid into the air-holes to tailor the fiber dispersion for slow-light propagation under low pulse distortion. In such a fiber made from Si material, group index n_g~8 is obtained with a bandwidth up to 30 nm, where the group index fluctuation is restricted in ±10 % of the ng, while n_g~6 is obtained with a bandwidth over 100 nm when the chalcogenide material is selected instead. Such a ±10 % criterion determines a regarded flatland region accordingly, and in this region the group velocity dispersion can be negligible. It is found that for the same fiber length the slow-light time delay in the photonic bandgap fiber is much larger as compared with that in the single mode fiber. This kind of photonic bandgap fiber may have many potential applications in short-distance fiber communications and delay lines.

An approach using fringe projection to perform the deformation measurement is proposed. A fringe pattern is illuminated onto the dynamic object, and a CCD camera is employed to record the fringe distribution. For a sufficient long recording time, fringes on the obtained image are deformed by the topography of the object, and also, blurred by motion. Thus, the blurred fringes supply additional information to describe the deformation during the measurement. Only one shot measurement is required for data processing. This makes it possible to perform the deformation measurements with low environmental vulnerability.

In this paper, we present an approach to enhance the image resolution by reassembling a couple of low-resolution images. Image registration was performed by the fringe projection technique. Experimental results have shown that accuracy better than sub-pixel of the low resolution camera can be achieved.

Dynamical sensing based on combination of classical optical effects and atomic force microscopy (AFM) presents challenge for analysis of the forces at the nanoscale and beyond. An interference effect between light reflected from an AFM cantilever and highly reflective silicon surface of the calibration grating was studied for relative humidity (RH) varied between 9 and 60%. Force-distance analysis indicates on separation of capillary, van der Waals, adhesion, and electrostatic forces. The measurements performed in contact AFM mode suggest that the period of interference pattern observed in displacement curves is a function of humidity and varies between 293 nm at RH = 9% and 335 nm at RH > 50% with standard deviation less than 8 nm. Clear change of the interference period suggests that other than hardwarerelated factors may be involved in the formation of the interference in force-distance curves.

Negative refraction has been the subject of considerable interest and it may provide the possibility of a variety of novel applications. Recently, it has been shown that photonic crystals (PhCs) composed of synthetic periodic dielectric materials can exhibit an extraordinarily high nonlinear dispersion which causes effects such as negative refraction and self-focusing properties that are determined by the characteristics of their photonic band structures and equal frequency contours (EFCs). In this paper we have theoretically studied the negative refraction in two-dimensional (2D) hexagonal lattices annular photonic crystal (APC) which composed of a dielectric-rod and a circular-air-hole array in a hexagonal lattice. By using Plane Wave Expansion (PWE) method and Finite-Difference Time-Domain (FDTD) method we have studied the photonic band structure, equal frequency contours and the electric field distribution of such photonic crystal. Numerical simulations show that negative refraction and superlense imaging can be realized in the designed annular photonic crystal.

Negative refraction attracted great interest and quickly became the subject of extensive worldwide research thanks to the many novel optical phenomena it can enable. One of the most exciting applications of negative refraction is the possibility of imaging with sub-wavelength resolution, which is often called superlensing. Recently, it has been shown that photonic crystals (PhCs) composed of synthetic periodic dielectric materials can exhibit an extraordinarily high nonlinear dispersion which causes effects such as negative refraction and self-focusing properties that are determined by the characteristics of their photonic band structures and equal frequency contours (EFCs). In this paper we have theoretically studied the negative refraction in two-dimensional (2D) triangular lattices graded photonic crystal (GPC) which constructed by varying the photonic crystal parameters so that its effective refractive index changes along the transverse direction of the slab. By using Plane Wave Expansion (PWE) method and Finite-Difference Time-Domain (FDTD) method we have studied the photonic band structure, equal frequency contours and the electric field distribution of the designed graded photonic crystal. Numerical simulations show that negative refraction and superlensing can be realized in the designed graded photonic crystal.

The effect of dopants in doubly-doped LiNbO₃ crystals on persistence of two-center recording is investigated experimentally and theoretically in this paper. Six kinds of doubly-doped LiNbO₃ crystals are used in experiments with 633nm recording and 404nm sensitizing, the results show that LiNbO₃:Ce:Cu crystal has the largest persistence. The dependence of persistence on bulk photo-voltaic coefficient and photo-excitation coefficient of deep center for recording light (K₁₂ and S₁₂) is discussed based on jointly solving the two-center material equations and the coupled-wave equations. The results show that both the increase of S₁₂ and the decrease of K₁₂ will result in the decrease of the persistence. When a holographic storage system is designed, the appropriate dopant will help to obtain the high persistence and dynamic range simultaneously.

Construction of optoelectronic memory arrays with signals optical input-output is the actual problem, because it allows removing from the record-storage- reading process ineffective optical-electronic and electronic-optical conversion. This increases the speed of the memory arrays. Construction of 2-D memory elements, based on optically controlled electroabsorption modulators with a large number of quantum wells using the quantum Stark effect, and vertical cavity surface emitting lasers (VCSEL) arrays is considered. The technology combining optically controlled electroabsorption modulators and VCSEL arrays for production cascades of connected 2-D arrays of memory based on developed optoelectronic asynchronous RS-trigger¹ and optoelectronic synchronous RS-trigger, which allows to create asynchronous and synchronous arrays of optoelectronic memory is suggested. Possibility of 2-D arrays aggregation is done by means of their serial connection due to appropriate organization of interconnections and by increasing the dimensionality via connection of similar 2-D arrays of both vertically and horizontally. Optoelectronic circuit memory cells based on optically controlled electroabsorption modulators and VCSEL arrays with the appropriate organization of interconnections. They can be built on the base of asynchronous RS-trigger and optoelectronic synchronous RS-trigger. The use of VCSEL with coupled cavities as input and output 2-D arrays for optoelectronic memory cascades is considered.

Thermal management had an important influence not only in the life time but also in the efficiency of high power light emitting diodes (HPLEDs). 30 watts in a single package have become standard to the industrial fabricating of HPLEDs. In this study, we fabricated both of the AlN porous films, by vacuum sputtering, soldered onto the HPLEDs lamp to enhance both of the heat transfer and heat dissipation. In our model, the ceramic enables transfer the heat from electric device to the aluminum plate quickly and the porous increase the quality of the thermal dissipation between the PCB and aluminum plate, as compared to the industrial processing. The ceramic films were characterized by several subsequent analyses, especially the measurement of real work temperature. The X-Ray diffraction (XRD) diagram analysis reveals those ceramic phases were successfully grown onto the individual substrates. The morphology of ceramic films was investigated by the atomic force microscopy (AFM). The results show those porous films have high thermal conduction to the purpose. At the same time, they had transferred heat and limited work temperature, about 70℃, of HPLEDs successfully.

A theoretical explanation of fixed holograms with high diffraction efficiency is given based on jointly solving the material equations and the coupled-wave equations. The dynamics of the recording and fixing diffraction efficiency can be effectively described and analyzed by using this method. The optimal recording wavelength for high fixed diffraction efficiency is discussed in detail. There is an optimal switching time for the maximum diffraction efficiency up to an ideal of 100%. Theoretical results can confirm the optimal recording wavelength for maximum diffraction efficiency of thermal fixing in Fe doped LiNbO₃ crystal.

We analyze the theoretical and physical properties of a CMOS compatible optical leaky wave antenna (OLWA) integrated into a Fabry-Pérot resonator (FPR) at 193.4 THz (wavelength λ₀ = 1550 nm). The presented OLWA design is composed of a silicon (Si) dielectric waveguide sandwiched between two silica glass (SiO₂) domains, and it comprises periodic perturbations (cavities of vacuum). We first describe the radiation of the isolated OLWA whose radiation pattern is due to the excitation of a leaky wave, slowly decaying while traveling. The perturbations are indeed designed to obtain a leaky wave harmonic with very low attenuation and phase constants. Then, we integrate the same OLWA into a FPR where two leaky waves with the same wavenumber are travelling in opposite directions inside the resonator. We show that the radiation level at the broadside direction can be effectively controlled by modifying the optical properties of the Si waveguide through electron-hole excess carrier generation (found to be highly enhanced when it is integrated into a FPR). The design of the integrated OLWA is properly set to guarantee the constructive interference of the two radiated beams provided by the two leaky waves in the FPR. The modal propagation constant in the integrated OLWA can be then altered through excess carrier generation in Si, thus the antenna can be tuned in and out of the resonance thanks to the high FPR quality factor, and the LW modal dispersion relation. This allows for enhanced radiation level control at broadside, and preliminary results show up to 13 dB beam modulation.

The antimony sulfoiodide (SbSI) single crystal being a ferroelectric semiconductor has a large number of interesting properties. Based on SbSI single crystal a new type of heterostructures has been produced. For the first time diodes, transistors and thyristors composed of SbSI/Sb₂S₃ heterojunctions have been fabricated by CO₂ laser irradiation of selected sections of SbSI single crystals. Treated sections are composed of amorphous antimony (III) sulphide (Sb₂S₃) with energy gap 0.3 eV smaller (in room temperature) than that of SbSI. The structural optical, electrical and photoelectrical characteristics of produced devices have been investigated.