We have developed several binary, ternary and quaternary sulfide and selenide crystals for nonlinear optical applications and present an overview on the crystal growth and characterization of crystals for nonlinear optical (NLO) conversion efficiency. We have summarized the performance of silver gallium selenide (AgGaSe₂), thallium arsenic selenide (Tl₃AsSe₃), and silver gallium germanium selenide (AgGaGe₃Se₈ and AgGaGe₅Se₁₂) crystals and have compared with gallium selenide (GaSe). All these crystals were grown by vertical Bridgman method in quartz ampoules by using stoichiometric compounds synthesized from constituent elements. The significant problem of cleaving of GaSe was reduced in ternary and quaternary compounds. Experimental results showed that binary, ternary and quaternary selenide compounds transmit at wavelengths up to 16 μm, have reasonably high value of nonlinear conversion merit (d²/n³, where d is the NLO coefficient and n is the refractive index) and have the lowest absorption coefficient compared to arsenides, phosphides and other nonlinear optical (NLO) materials.

A technique which takes advantage of distributed feedback laser diode (DFB-LD) wavelength scanning to measure water vapor concentration is presented. Concentration is gotten by peak absorption rate according to Beer-Lambert law and absorption coefficient of water vapor in HITRAN database. Theoretical work on the pressure affection to light intensity absorption rate has been done, a scheme is presented to cope with the affection of overlap of two adjacent lines, it takes advantage of the peak absorption difference between 1368.597nm and 1367.862 nm, and the difference value is used to calculate the water-vapor concentration.

In this work we present results of physical and optical properties of Er³⁺-Yb³⁺ co-doped tellurite glasses and fibers. The Double Clad Tellurite Fibers (DCTFs) are based on glasses with the composition: TeO₂-WO₃-Nb₂O₅-Na₂O-Al₂O₃-Er₂O₃-Yb₂O₃. The DCTFs were fabricated by using the rod-in-tube technique and a Heathway drawing tower. The optical absorption spectra (ranging from 350 to 1750 nm) of these fibers were measured using an Optical Spectrum Analyzer (OSA). The emission spectra, around 1550 nm band, of these fibers (lengths varying from 1 to 60 cm) were obtained by using a 980nm diode laser pump. The optimal Amplified Spontaneous Emission (ASE) spectra were observed for fiber lengths ranging from 2 to 6 cm. The Er ³⁺/Yb³⁺ co-doped DCTFs show an efficient up-conversion process in comparison with the Er³⁺-doped DCTF.

One investigates a light localization at laser pulse propagation in 1D (layered) or 2D nonlinear photonic structure. The light localization takes place due to appearance of spatial solitons which velocities depend on their intensities and location in the photonic crystal. This results in changing of velocities of sub-pulses which are not soliton and reflect or transmit through the nonlinear photonic crystal. We found out the formation of two types of solitons. One of them is appeared in separate layer. This soliton appear because of cubic nonlinear response. The second type of soliton spreads over some layers of the photonic crystal. This soliton is found out on the base of solving the eigenvalue function. We consider also the Anderson localization in photonic crystal with nonlinearity. The main result of this part of the investigation is a prevalence of nonlinear localization over the Anderson localization. The formation of soliton depends on input light intensity, duration of pulse and shape of elements from which the photonic crystal consists. In 2D case the soliton formation depends on focusing of laser beam and on presence of laser energy in neighbouring elements of the photonic crystal. These solitons move with slow velocity inside the elements of the photonic crystal. Under certain conditions the soliton can stop. This phenomenon can be used for data storage. The similar solitons can appear in many elements of the photonic crystal.

All-optical switching and regeneration based on optical Kerr effect are feasible in single and coupled-cavity thin film structures comprised of high-index and low-index materials. In this report we will present a simulated Kerr effect nonlinear function switching from low to high transmissions at telecom wavelength using an optimized coupled cavity structure. This nonlinear transfer function has multiple high transmission peaks suitable for all-optical switching and regeneration detection at high transmission state. Successful fabrication of single and coupled-cavity dielectric thin film structures for 800 nm were achieved with low refractive index (n=1.46) SiO₂ and high refractive index (n=1.90) SiN by RF PVD. The simulated transmissions of the samples match almost exactly with the measured transmissions by VASE ellipsometer. The strategy of precision control of central wavelength of the resonant structure was implemented and good results were attained. The RMS surface roughness of RF sputtered and pulsed DC sputtered thin films are investigated by AFM. Suitability of nonlinear materials for ultrafast optical Kerr effect nonlinear refractions will be briefly discussed.

Epitaxial BaTiO₃ films were deposited by using innovative double-pulse--lasers Deposition (DPLD) technique. The modified DPLD enables the ablation of batio3 thin film to be doped with Fe and Mn in situ during the ablation process. Different substrates were used like MgO, SrTiO₃, and Si to decrease the misfit with BaTiO₃. The films deposited at different substrate-temperature in the range of 200°C-800°C. The thin film surface morphology was investigated using both Atomic Force Microscope (AFM) and Reflection high Energy Electron Diffraction (RHEED). The substrate temperature and the oxygen gas pressure affected the morphology of the thin film and in turn the optical response of the thin film. The AFM reviled a new harmonic grating structure of the thin film due to the DPLD ablation. The thin film shows an anomalous response to the HeNe laser as a self-modulation and grating formation pattern were observed.

We have investigated photoinduced redistribution of metal nanoparticles, placed on the surface of the ferroelectric photorefractive crystal during recording of dynamic holograms. Motivations for this study were improvement of sensitivity for recording of dynamic holographic gratings, for application in nondestructive testing of materials. The home- made biosynthesized gold and silver colloidal solutions were spread as a thin layer on the ferroelectric photorefractive crystal surface. Holographic gratings were recorded in photorefractive crystal of Fe:LiNbO₃(Fe:LN) by the HeNe laser (λ=633nm) to avoid direct influence of laser light on nanoparticles. Photorefractive holographic grating initially recorded in the crystal volume produce spatially modulated electric field on the crystal surface. This field led to electrophoretic redistribution of the nanoparicles on the crystal surface that result also in additional contribution to the electric field pattern and also change diffraction efficiency of hologram. In addition, we have recorded holographic grating in Fe:LN placed in 5mm cuvette with silver nanoparticles nanofluid and observed nanoparticles distribution along grating line. We have calculated electrophoretic (EP) and dielectrophoretic (DEP) forces on the crystal surface with holographic photorefractive grating, recorded in the crystal. It is shown that longitudinal (along the crystal surface) components of the DEP-force can be described only with high-contrast approach.

Epitaxial thin films of Barium Ferrite (BaFeO3) have been fabricated by the pulsed laser deposition technique on a Si substrate. The magnetic parameters were measured using vibrating sample magnetometer. The ferromagnetic resonance (FMR) measurements of the thin film were found to be close to the parameters associated with bulk materials. The Atomic Force Microscope was used to determine the surface morphology at different temperatures. The derivative FMR line width was measured to be 70 Oe at 60 GHz and 50 Oe at 90 GHz. The relationship among the Coercivity, crystalline orientation, and grain shape and size is presented.

The unusual thermophysical properties of the CdZnTe crystals (high melt viscosity, a large latent heat of fusion, fairly large equilibrium segregation coefficient, etc.) cause considerable difficulty in maintaining uniform zinc composition in the grown crystal. The disadvantages can be overcome by the dewetted Bridgman technique in which the crystal is grown detached from the ampoule wall by a liquid free surface at the level of the solid-liquid interface, called liquid meniscus, which creates a gap between the grown crystal and the ampoule wall that bring together low contact stress with low thermal stress. Crystal growth experiments showed that, in some conditions, chemical impurities at the liquid surface may lead to unintended contamination that can increase the wetting angle artificially. This high sensitivity of the wetting angle changes the meniscus shape, and hence the dopant distribution in the grown crystal. For evaluating numerically the effect of the menisci shapes on the Zn distribution in CdZnTe crystals grown by dewetted Bridgman technique, a pseudo quasi-steady state model is considered in the framework of a 2D axisymmetric geometry containing two types of stable menisci: (i) a "S" shape meniscus that corresponds to the sum-of-the-angles criterion α_e+θc<180° (α_e is growth angle and θ_c is wetting angle); (ii) a globally convex meniscus that corresponds to chemical contamination, i.e., α_e+θc>180°. Numerical computations including incompressible fluid flow in the Boussinesq approximation, heat and mass transfer, and Marangoni effect, are performed using finite element technique. It is proven that a convex meniscus assures the best impurity distribution.

In this study, we demonstrate method for quasi phase matched silicon-on-sapphire waveguides suitable for MWIR wavelength conversion to achieve higher conversion efficiency than that can be achieved in uniform waveguide geometries. In particular we show that periodic change in waveguide width by 0.5μm and hence periodic change in waveguide dispersion can to reset phase accumulation and provide ever-increasing gain profile. With the fabrication flexibility of large cross-section of MWIR waveguides, the possibility of using quasi-phase-matching can provide >30dB conversion efficiency enhancement and increase the conversion bandwidth by 2 times. Such improvement may facilitate the fabrication of parametric oscillators that can improve the conversion efficiency by 50dB.

An optical leaky wave antenna (OLWA) is a device that radiates a light wave into the surrounding space from a leaky wave (LW) guided mode or receives optical power from the surrounding space into a guided optical mode. In this work, we propose and provide a 3D analysis of a novel CMOS compatible OLWA made of a silicon nitride (Si₃N₄) waveguide comprising periodic silicon perturbations which allow electronic tuning capability. The analysis presented here includes the effect of the number of semiconductor perturbations, the antenna radiation pattern and directivity. We show that the number of the silicon perturbations has to be large to provide a long radiating section required to achieve radiation with high directivity. In other words, the proposed structure allows for a very narrow-beam radiation. Preliminary results are confirmed by exploiting leaky wave and antenna array factor theory, as well as verified by means of two full-wave simulators (HFSS and COMSOL). Our purpose is to ultimately use PIN junctions as building blocks for each silicon implantation for the electronic control of the radiation. In particular, the electronic tunability of the optical parameters of silicon (such as refractive index and absorption coefficient) via current injection renders itself the ideal platform for optical antennas that can facilitate electronic beam control, and boost the efficiency of optoelectronic devices such as light-emitting diodes, lasers and solar cells, and bio-chemical sensors.

The effects of different slow-down factors on two photon absorption and free carrier absorption in silicon-on-insulator (SOI) photonic crystal (PhC) channel waveguides are reported in this paper. It is found that, in the slow light regime, these nonlinear effects are enhanced, but that the enhancement produced depends on the input peak power level. Simulations indicate the possibility of soliton-like propagation of 111 fs pulses at 1.55 μm inside such a photonic crystal waveguide.

In this paper, we report our investigations on real-time holographic recoding at 1064 nm in Ru-doped bismuth sillenite crystal with a green gating light at 532 nm. By using gating light significant improvement of the response time to 80 ms is achieved and the prolonged read-out process of the recorded hologram is observed. We also demonstrate quasipermanent holographic recording of image with fast speed in Ru-doped BSO crystal using two-wavelength recording.

Directionally reflective fiber arrays were woven with polymer fibers. Fiber cross sections produced using a tricomponent fiber extruder comprised standard circular as well as right angle retro-reflection features that run the entire length of the fiber. The fiber features are formed by an extrusion process where the polymer fiber material is forced through a series of plates resulting in the cross section having the desired shape. The woven fiber arrays were evaluated for their optical properties. Results for spectral reflectivity and spatial reflectance signature properties are presented. A comparison of the results obtained for the woven fiber arrays and those obtained for bundles of similar fibers are discussed. The implementation of fiber arrays through the use of weaving techniques allows for the realization of a number of unique and useful optical effects. As evidenced by the spectral measurements, the color of the woven arrays can be controlled by a number of means: for example by the inclusion of dyes, nanoparticles, and by post-processing applications of thin films. The present work represents a logical extension of previously reported experiments with unwoven fibers with retro-reflective features1.

In this work we show results of controlled tapered fibers using a Vytran instrument. The tapered silica fibers were produced by pulling a 50μm length by heating time. The minimum taper diameter was around 3μm and the maximum taper length was around 600μm. The evanescent field effect, in the near infra red (NIR) region, was observed to the tapers with diameter inferior to 15μm. These micro-size tapers no modify the waveguide dispersion spectra. This device could be used to splice a conventional fiber to photonic crystal fibers and also as liquid and gas sensors In this work is reported a fiber optic sensor in the form of taper using the concept of the evanescent field. We show the sensor sensitivity using different liquid materials.

Saving energy, White-light LED plays a main role in solid state lighting system. Find the best energy saving driven solution is the engineer endless hard work. Besides DC and AC driving, LED using Pulse Width Modulation (PWM) operation is also a valuable research topic. The most important issue for this work is to find the drive frequency and duty for achieving both energy saving and better feeling on the human vision sensation. In this paper, psychophysics of human vision response to the lighting effect, including Persistence of vision, Bloch's Law, Broca-Sulzer Law, Ferry-Porter Law, Talbot-Plateau Law, and Contrast Sensitivity, will be discussed and analyzed. From the human vision system, we found that there are three factors: the flash sensitivity, the illumination intensity and the background environment illumination, that are used to decide the frequency and duty of the PWM driving method. A set of controllable LED lamps with adjustable frequency and duty is fitted inside a non-closed box is constructed for this experiment. When the background environment illumination intensity is high, the variation of the flash sensitivity and illumination intensity is not easy to observe. Increasing PWM frequency will eliminate flash sensitivity. When the duty is over 70%, the vision sensitivity is saturated. For warning purpose, the better frequency range is between 7Hz to 15Hz and the duty cycle can be lower down to 70%. For general lighting, the better frequency range is between 200Hz to 1000Hz and the duty cycle can also be lower down to 70%.

With quickly advance of the computer, microelectronics and photonics technologies, LED display panel becomes a new electronic advertising media. It can be used to show any information whatever characters or graphics. Most LED display panels are built of many Light-Emitting Diodes arranged in a matrix form. The display has many advantages such as low power, low cost, long life and high definition. Because the display panel is asked to show rich color, the LED display panel's driving system becomes very complex. The design methodology of LED display panel's driver becomes more and more important to meet the market requirements. Cost is always the most important issue in public market domain. In this paper, we report a design methodology of LED display panel's driver based on the microprocessor control unit (MCU) system and LED display controller IC, HT1632C, to control three colors, RGB, color LED display panel and the modular panel size is 24*16 in matrix form. The HT1632C is a memory mapping LED display controller, it can be used on many applications, such as digital clock, thermometer, counter, voltmeter or other instrumentation readouts. Three pieces of HT1632C are used to drive a 24*16 RGB LED display panel, in our design case. Each HT163C chip is used to control one of the R, G and B color. As the drive mode is driven in DC mode, the RGB display panel can create and totally of seven colors under the control of MCU. The MCU generates the control signal to drive HT1632C. In this study, the software design methodology is adopted with dynamic display principle. When the scan frequency is 60Hz, LED display panel will get the clear picture and be able to display seven colors.

In recent years photonic crystals have become a favored area of research due to their diversified applications. In this paper we propose a mathematical model for analyzing the photonic band gap of a 1D binary photonic crystal (GaAs and air) which allows us to use it effectively as a photonic tuner which is an integral part of any optical amplifier. As optical parameters like reflection and refraction follows similar pattern from each plane within a photonic crystal, we can take help of characteristic matrix for a single plane and multiply (m) times where the crystal consists of (m) periods. Using the fact that the characteristic matrix comes out to be unimodular and taking help of Cayley-Hamilton theorem and Chebyshev polynomials, we expand the matrix of the entire system to derive the location and width of photonic band gaps. Higher stop bands occur at lower frequency of incoming radiation and central bandgap wavelength decreases with increasing angle of incidence. The power transmitted by the tuning crystal decreases for radiations away from normal. Using a polarizer model, the attenuation is computed to be proportional to log|Cos2θ|, where θ is the angle of incidence. The mathematical modeling developed can also be extended for realization of n-array photonic crystal. We have also considered the refractive index modulation with respect to temperature for using it as a temperature sensor.

Four-wave mixing (FWM) in silicon waveguides is considered to be a promising effect to realize the wavelength conversion function for wavelength-division-multiplexing optical communication systems. Compared to the degenerate FWM with a single pump, the nondegenerate FWM with two pumps shows more flexibility in phase-matching condition and has more opportunities to acquire broader conversion bandwidth. The bandwidth enhancement is theoretically analyzed for the two-pump FWM and an enhancement of 25% is experimentally demonstrated. Also, an ultra-broadband wavelength conversion is presented based on two-pump FWM by fixing one pump near the signal and scanning the other pumps.

Fringe projection techniques are powerful tools to find the 3D profile of an object. However, color on the inspected object might be damaged due to the fringe projection. In this paper, we investigate three approaches to recover the color distribution. This makes it possible to enhance the performance of 3D image vision.

A read-only volume holographic correlator (VHC) is proposed. After the recording of all of the correlation database pages by angular multiplexing, a stand-alone read-only high accuracy VHC will be separated from the VHC recording facilities which include the high-power laser and the angular multiplexing system. The stand-alone VHC has its own low power readout laser and very compact and simple structure. Since there are two lasers that are employed for recording and readout, respectively, the optical alignment tolerance of the laser illumination on the SLM is very sensitive. The twodimensional angular tolerance is analyzed based on the theoretical model of the volume holographic correlator. The experimental demonstration of the proposed read-only VHC is introduced and discussed.

Plasmon like excitation is observed at the interface between one-dimensional periodic array of air holes in silicon (Si) with ferroelectric polyvinylidene fluoride (PVDF) as a substrate to obtain subwavelength confinement of surface Plasmon modes at terahertz (THz) frequencies. A truly Plasmonic TM mode is obtained confined at the interface of PVDF layer and the 1D perforated dielectric slab and the mode field distribution of the structure is demonstrated using three dimensional (3D) Finite Difference Time domain Method (FDTD) method. It is shown that PVDF are promising materials for strongly confined THz wave propagation in Surface Plasmon photonic crystal. The transmission, confinement and hence the propagation length of the plasmonpolariton like terahertz surface modes sustained by the structure are studied using Finite difference time domain (FDTD) method. Further, the propagation characteristics of surface Plasmon polariton (SPP) which can be controlled by the structure geometry is discussed.

An experimental investigation on a novel electrically controlled optical chopper based on holographic polymer dispersed liquid crystal (H-PDLC) gratings is presented in this paper. In order to realize the chopping function, a corresponding electrical driving source and controlling circuit are developed for the phase type H-PDLC grating, so that the H-PDLC chopper can not only modulate a light beam with variable frequencies at different duty ratios but also generate other types of waveform modulation such as the sinusoidal modulation to replace the traditional rectangular modulation. Experimental results on one-channel, two-channel and four-channel H-PDLC optical choppers showed that, in comparison with the mechanical chopper counterpart, this device had the advantages of (1) lower noise without mechanical moving part, (2) higher conveniences in terms of changing its operational frequencies, duty ratios and modulation curves, and (3) multi-channel modulation capability. Therefore, it will have a great potential for applications that requires frequency modulations such as frequency modulated confocal microscopy system.

A kind of single-polarization and single-mode photonic crystal fiber (SPSM PCF) is proposed in this paper. It is a PCF structure with elliptical air holes in the cladding and four large holes introduced in the first ring. A full-vector plane wave expansion method is employed to analyze this PCF structure. The numerical results show that this PCF structure can realize ultra-broad SPSM bandwidth as 540nm with the confinement loss less than 0.1dB/km, the broadest bandwidth as far as our knowledge goes.

Maximum fixing efficiency of thermal fixing in LiNbO₃:Fe crystal is investigated. Based on Kukhtarev's band transport model and Kogenlik's theory, the mechanisms leading a high diffraction fixed hologram in LiNbO₃:Fe crystal is analyzed. To obtain a volume grating with the maximum fixed diffraction efficiency, the optimal switching from recording step to thermal fixing is taken into consideration. With the same oxidation state and dopant concentration, the developed efficiency for low light intensity depended on the recording wavelength. Holographic gratings are recorded using three typical recording wavelengths including 488nm, 514nm, and 633nm respectively. The fixed holograms are developed by original recording setup. Diffraction efficiencies of recording and thermal fixing are measured by two-wave coupling technique. Both experimental results and theoretical simulation are presented. Through the theoretical and experimental results analyzed and compared, the blue beam was the optimal recording wavelength for maximum fixing efficiency of thermal fixing in LiNbO₃:Fe. This work can obtain high persistent diffraction of the nonvolatile holographic storage in LiNbO₃:Fe crystals.

A fringe projection technique for finding the absolute shape at a sequence of time for a dynamic object is proposed. This method makes it possible to simultaneously identify the trace and the speed of the dynamic object.

We present a database system based on the empirical mode decomposition (EMD) to automatically reduce the speckle in a fringe pattern. With reference to the database, speckles on the fringe pattern can be efficiently and robotically reduced. Percentage of the removed speckles can be predicted as well.

A profile measurement approach using two diffractive elements to generate two fringe patterns is presented. Only one phase measurement needed for operation. In conjunction with the endoscope, the compact design makes it possible to inspect dynamic object inside the body cavity.

The effect of variable sensitizing intensity on photorefractive performance in two-center recording is investigated through jointly solving two-center material equations and the coupled-wave equations. Four kinds of schemes for varying sensitizing intensity are designed, the relationship between the sensitizing intensity and recording time is simply assumed to be linear, and at the same time the recording intensity is stable in recording process. The temporal evolution of the space charge field (SCF) is obtained in each scheme. The results show that SCF increase monotonously no more in the recording process. The increase of sensitizing intensity will reduce the peak value of SCF during recording process. However, the decay of sensitizing intensity can enhance the peak value of SCF. The slow decay of sensitizing intensity is also useful to the buildup of high SCF, but the recording time will be long. At last, the effect of the decay mode and the initial value of sensitizing intensity on recording process are discussed. Both of recording sensitivity and the peak value of SCF can be enhanced in decay scheme with the high initial sensitizing intensity. In a real application an appropriate sensitizing light scheme needs to be designed.

New Airy beam manipulation method based on the metallic slit array is presented. By controlling the phases and intensities of the transmitted lights from each subwavelength metallic slit via the variations of the parameters such as widths, heights, positions, and numbers of the slits, the overall phase and intensity distributions of the transmitted light are designed to mimic that of Airy beam. The proposed method can effectively produce the Airy wave packet in microscale without any spatial light modulator (SLM) and lens. The numerical result and considerations on the design method to make compact structure to generate the Airy wave packet will be presented.

We report on the effect of transient selfheating on the spectral modulation of electroluminescence (EL) in high-power light-emitting diodes (LEDs). In AlGaInP LEDs, which emit due to the band-to-band recombination of free carriers, the oscillation of junction temperature was found to result in that the modulation depth has a drop around the peak photon energy, an increased magnitude at lower energies, and a linear increase with photon energy at higher energies. These properties of the EL modulation spectrum can be explained by a model that takes into account the thermal modulation of band gap energy and carrier distribution function. In InGaN LEDs, almost no thermal effect on EL modulation was found around the peak photon energy and at lower energies, whereas at higher energies, the modulation depth also increases with photon energy. Such a spectrum of EL modulation depth can be understood in terms of localized carrier effect at peak photon energy and lower energies and of free carrier heating at higher energies. The frequency dependence of modulation depth at particular photon energies was shown to sensitively replicate the thermal response function of the LEDs.

We present two approaches for production of periodically poled lithium niobate crystals by surface modification of congruent crystals: first - by Li enrichment during annealing and second - by deposition a thin layer of stoichiometric lithium niobate film on the +Z face of a crystal. Both methods have allowed to create on the surface of congruent sample a layer with composition close to stoichiometric and to reduce a poling electric field without changing of the composition of crystal volume and thereby to keep all advantages of congruent crystal.

Dispersion and resonance properties of double nanorod structure, ring structure, H structure and chair type structure is demonstrated. With some structural modification, the properties of the structure changes from isotropic to uni-axial anisotropic and further to chiral left-handed material. The Demonstration of near-field transmission spectrum reveals the production of the local-field enhancement up to 10² for the green light. Negative real values of both permeability (μ) and permittivity (ε) for visible light are obtained by applying coupled dipole approximation. The structure modification exhibits some unique dispersion and resonant properties that may govern imaging applications.

In this paper, soliton pulse generation and collision in chalcogenide As2Se3 glass Photonic Crystal Fiber (PCF) is numerically studied using our own algorithm developed for Fourth-Order Runge-Kutta in the Interaction Picture (RK4IP) method. The numerically obtained value of soliton collision length is found to be in good agreement with the theoretical value obtained by the inverse scattering transform, thus providing a verification of the accuracy of the method in solving Generalized Nonlinear Schrödinger Equation (GNLSE). We also calculate the value of wavelength for least distortion for soliton optical pulses.

In the paper, we investigated the bistable properties of the wideband optical filter on the basis of nonlinear 2D photonic crystal. All-optical flip-flop phenomena have been discovered in such filters which allows switching with ultra-short pulses. Particularly, the attention in this work is paid to the filter characteristics stability as respect to radiation parameters variation as well as to production defects.

The amplitude of terahertz radiation (THz) from a series of oxide films on GaAs was measured by time resolved THz emission system. The barrier heights and the densities of the interfacial states are determined from the PR intensity as a function of the pump power density. The oxide-GaAs structures fabricated by in situ molecular beam epitaxy exhibit low interfacial state densities in the range of 10¹¹ cm^-2. It is found that the amplitude of THz radiation from Al₂O₃^-, Ga²O^3-, and Ga₂O₃(Gd₂O₃)-GaAs structures are increases with interfacial electric field. The reason is that the electric field is lower than the "critical electric field", the amplitude is proportional to the product of the electric field and the number of photo-excited carriers. However, as the field higher than the critical electric field, sample of air-GaAs structure, the lower THz amplitude was obtained due to the maximum drift velocity declines slightly as the field increases.

In this paper, three types of scanner which their width are varied with parabolic, hyperbolic and exponential functions are studied. The equations of deflection angle and ray trajectory of three types of electro-optic scanner are given and their deflection properties are investigated by numerical analysis. The deflection characteristics and sensitivities are compared to each other. It is helpful for the design of electro-optic scanners with fine performance.

Room-temperature contactless electroreflectance (CER) was used to investigate the optical properties of a N,N'-didecylperylene-3,4,9,10-tetracarboxylic diimide (PTCDI-C₁₀H₂₁) thin-film sandwiched between indium tin oxide and aluminum electrodes (Al/PTCDI/ITO/glass substrate) under vacuum conditions. The electromodulated optical responses of the Al/PTCDI/ITO/glass structures were characterized by various alternating current biases. The optical transitions of PTCDI were perturbed by energy shifts of electronic states due to the Stark effect induced by the modulated electric field. The modulated CER spectrum of PTCDI is strongly enhanced by performing first derivatives on the absorption spectrum of PTCDI. The CER spectrum involves fundamental transitions, doping states, and Davydov splitting. Moreover, the intensity of the field-induced transition peak of PTCDI increases with increasing CER modulation voltage. The transition energies between the lowest unoccupied molecular orbital and highest occupied molecular orbital of the Al/PTCDI/ITO system is obtained from the peak positions in the CER spectrum.

A plasmonic cavity incorporating surface plasmon polariton(SPP) mode is proposed to be used as infiltrated sensor employing sub-wavelength confinement of light. Truly Plasmonic TM mode is obtained and the mode profile of the Plasmonic Photonic Crystal Cavity (PPCC) structure is shown using three dimensional Finite Difference Time Domain Method (3D-FDTD) method. The cavity length of the structure is optimized to obtain single mode localization of resonating wavelength and the change in the cut-off wavelength is observed by varying refractive indices of the content of air holes. A transverse magnetic (TM) Plasmonic bandgap of the structure is shown and hence, the transmission spectra, Quality factor are calculated.

The temperature had an important influence in the life time of light emitting diodes (LED). In this study, we fabricated the ceramic porous films, by vacuum sputtering, soldered the LED lamps to enhance both of the heat transfer and heat dissipation. In our samples, 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 substrate. The morphology of ceramic films was investigated by the atomic force microscopy (AFM). The results show porous film fabricated by vacuum sputtering has high sheet resistivity, critical load, and thermal conduction to the purpose. At the same time, it had transferred heat and limited work temperature, ~80°C, of LED successfully.

In this work we present the laser performance of channel waveguides which operate at 1064 nm at room temperature. These channels were made on Nd: YAG crystal by proton implantation with different widths (10, 15 and 20 μm) forming sets of 10 waveguides which are separated by a distance of 215 μm. The results shown are transversal mode distribution, propagation losses, absorption and luminescence spectra and laser emission characteristics such as pump power threshold and slope efficiency. The spectroscopic characterization indicates that the optical properties of the waveguide in comparison with the bulk material are preserved after the implantation process and that this is a potential technique to develop compact and efficient lasers.

We propose a resonant optical Yagi-Uda nano-antenna fabricated at the end of the optical fiber probe for the sake of extracting the information of the angular directivity by absorption of directional emission as a subwavelength optical microscopy. A Yagi-Uda nano-antenna consists of a feed element surrounded by a reflector and three directors. The reflector and directors are optimized in pitches with regards to resonance of the antenna elements using the finiteelement method. We used a focused ion beam (FIB) to cut the end of the fiber probe tip away and make the flattened surface to mount the metal nano-antenna structure, followed by FIB platinum deposition patterning for the nano-antenna. To verify the characteristics of the probe based nano-antenna, directional emission from the metal slit with asymmetric metallic surface gratings is probed and detected using the photomultiplier tube. Our approach of the nano-antenna based fiber probe is suitable for scanning applications such as detection of directional emission.

In this paper, the growth of ZnO/MgZnO composite structures with a larger number of periods by pulsed laser deposition is presented. The structural and physical properties are quantitatively characterized by field-emission scanning electron microscopy, transmission electronic microscopy, X-ray diffraction, and photoluminescence. It is demonstrated that the quantum confinement effect has been observed from the composite structures at room temperature. The applications of this unique ZnO/MgZnO composite structure are also discussed.

The method by applying the interfered femtosecond laser to create nanostructured copper (Cu) surface has been studied. The nanostructure created by direct laser irradiation is also realized for comparison. Results show that more uniform and finer nanostructures with sphere shape and feature size around 100 nm can be induced by the interfered laser illumination comparing with the direct laser illumination. This offers an alternative fabrication approach that the feature size and the shape of the laser induced metallic nanostructures can be highly controlled, which can extremely improve its performance in related application such as the colorized metal, catalyst, SERS substrate, and etc.

A technique of enhancing terahertz (THz) wave radiation from large aperture photoconductive (PC) antenna is presented in this paper. In this technique, the PC antenna is excited by both the optical and previously-generated THz pulses by a laser induced air plasma created in front of PC antenna, an enhanced THz wave signal is obtained. The technique shown in this paper can be very useful for THz imaging and spectroscopy.

In recent years, much of effort has been devoted in the field of optical switches, including electro-optics (EO), magnetooptics (MO), acousto-optics (AO), liquid crystal (LC), and microelectromechanical systems (MEMS). However, issues which involve switching speed, aperture size, and extinction ratio cannot be simultaneously settled by the present approaches. The paper proposes a novel optical switch based on tunable photonic metamaterial. By the controllable external electrical or magnetic field, the nano-structure is forced to vary its optical properties to be an optical switch. The theoretical studies suggest that the device could offer the merit features of ultra-fast speed, large aperture, and high extinction ratio. In the future, we will not only thoroughly model the proposed devices, but investigate kinds of possible fabrication process to implement the design. To be a next-generation optical switch, the tunable photonic metamaterial has large potential in several civilian applications, including mobile high-speed display, free-space optical communication, solar concentration, and the optical printing.

Tunable photonic crystals (PCs), which are infiltrated with nematic liquid crystals (LCs), tune photonic band gap (PBG) by rotating directors of LCs when applied with the external electrical field. Using the plane wave expansion method, we simulated the PBG structure of two-dimensional tunable PCs with a triangular lattice of circular column, square column and hexagon column, respectively. When PCs are composed of LCs and different substrate materials such as germanium (Ge) and silicon (Si), the influence of structural parameters including column shape and packing ration on PBG is discussed separately. Numerical simulations show that absolute PBG can't be found at any conditions, however large tuning range of polarized wave can be achieved by rotating directors of LCs. The simulation results provide theoretical guidance for the fabrication of field-sensitive polarizer with big tunable band range.

The optical chopper array based on Holographic Polymer Dispersed Liquid Crystal (H-PDLC) working at high frequencies, for example 1KHz, 2KHz, and its application in an improved Frequency Division Multiplexed Fluorescence Confocal Microscope (FDMFCM) system are reported in this article. The system is a combination of the confocal microscopy and the frequency division multiplexing technique. Taking advantages of the optical chopper array based on H-PDLC that avoids mechanical movements, the FDMFCM system is able to obtain better Signal-Noise Ratio (SNR), smaller volume, more independent channels and more efficient scanning. What's more, the FDMCFM maintained the high special resolution ability and realized faster temporal resolution than pervious system. Using the proposed device, the FDMFCM system conducts successful parallel detection of rat neural cells. Fluorescence intensity signals from two different points on the specimen, which represent concentration of certain kind of proteins in the sample cells, are achieved. The experimental results show that the proposed H-PDLC optical chopper array has feasibility in FDMFCM system, which owes to its unique characteristics such as fast response, simple fabrication and lower consumption etc. With the development of H-PDLC based devices, there will be prospective in upgrading FDMFCM system's performance in the biomedical area.

A novel photonic magnetometer for a variety of applications is being developed. The detection mechanism is similar to existing fiber optic magnetometers, in which a magnetostrictive element transduces magnetic field variations into changes in optical path length, subsequently detected through optical interferometry. Single-axis and three-axis vector magnetometers have been designed, and other application-specific configurations have also been investigated. The sensor noise floor is estimated at 20 pT/√Hz for frequencies of 0.1 Hz and above, with a dynamic range of over 100,000 nT. The sensor can be compact (down to 1 cm³) and can consume less than 100 milliwatts of power. These features, combined with its low 1/f noise and wide dynamic range, make the photonic magnetometer an easily deployable detector of low-frequency magnetic fields. Potential applications of the novel photonic magnetometer, including space-based measurement of geomagnetic fields, medical biomagnetic imaging, vehicle detection, mine detection, heading sensors, low-frequency communications, and deep eddy current nondestructive evaluation, have been explored as well.

Integrated Optical Ring Resonator structures fabricated on SOI (silicon-on-insulator) based on MEMS (micro electronic mechanical system) present provide feasibility for highly compact and low cost integrated optical devices. The SOI Integrated Optical Micro Ring Resonator was designed and fabricated in this paper. We designed bending radius of 15μm optical ring resonator. Most important we designed vertical grating coupler for increasing the coupling efficiency between the single mode fiber and waveguide. We get obvious coupling of SOI Integrated Optical Micro Ring Resonator to single mode waveguide in experiments. Without any optimization processing the quality factor(Q) of micro ring resonator is demonstrated as high as 1.5×10⁴ -1.93×10⁴.

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, the transmission characteristics of a new type of IR fibers is presented. Furthermore, the SCG generation in this new type of optical fiber is experimentally demonstrated. Finally, the suggestion for the future effort is discussed.

Potassium lithium tantalate niobate single crystals with the composition of K_0.95Li_0.05Ta_1-x Nb_xO₃ (KLTN) 0.4<x<0.9, have been grown using the top seeded melt growth method. The dielectric, pyroelectric, and piezoelectric properties have been systematically investigated earlier to establish the quality of the crystals. Using the minimum deviation method the indices of refraction as a function of frequency at room temperature and the Sellmeier's dispersion parameters are determined. The Sénarmont compensator method and a modified Mach-Zehnder interferometer configuration were coupled with computer interfaced dynamic scanning to measure the linear (Pockels') electrooptic coefficients. Large electro-optic responses are obtained for the crystal with K _0.95Li_0.05Ta_0.4Nb_0.6O₃ composition at 1kHz: r₃₃ =216.7 [pm/V], r₁₃ = -21.2 [pm/V], and r_C= 242.9 [pm/V]. The high EO coefficients, high figure of merit (as EO modulator), and high laser damage threshold are some of the attractive features for their attractive applications as electro-mechanical-optical coupled devices.