Contactless electroreflectance (CER) of a GaN/InGaN/AlGaN multilayer structure grown on sapphire has been measured in the temperature range of 15K and 450K. Except for the GaN exciton structures, well-defined Franz-Keldysh Oscillations are observed above the AlGaN band gap. An electomodulational model based on complex Airy functions is used to analyze the FKOs line shape. The temperature dependence of transition energies is obtained both for GaN and AlGaN. The magnitude of the built in electric field in AlGaN layer is also determined. The temperature dependence of the electric field is found to be consistent with the variation of thermal strain in the epilayer. It is demonstrated that the built-in electric field can be identified to be due to the piezoelectric effect.

GaN thin films, undoped, Si- and Mg-doped, and InGaN-GaN multiple quantum well (MQW) structures have been grown on Si substrates with specially designed composite intermediate layers consisting of a ultra-thin amorphous Si layer and a GaN/AlGaN multilayered buffer by low pressure metalorganic chemical vapor deposition. The structural and optical properties of these new grown material were studied. X-ray diffraction, Raman scattering and Fourier transform IR reflectance measurement confirmed their wurtzite structure. Scanning electron microscopy exhibited the single crystalline grain size up to approximately 2 micrometers . Photoluminescence showed strong GaN near edge emission, with only very weak deep defect-related emissions, for GaN films, and strong MQW emissions. The film surface morphology and material properties are improved by adjusting the growth conditions and buffer layer structural design.

InGaN thin films were grown by low-pressure metalorganic chemical vapor deposition and characterized by photoluminescence with variable excitation intensity and temperature, room-temperature cathodoluminescence (CL), high resolution X-ray diffraction, scanning-electron-microscopy (SEM) and atomic force microscopy (AFM). For PL, all the sample show dominant peaks at around 2.9 eV and extra peaks or shoulders at 2.8 eV at 6K. We concluded that the low energy peak is due to the localized near-band edge transition from the phase-separated InGaN mesoscopic structure with high In-content. The strong luminescence of the low of nanostructure or quantum dots. AFM images showed that phase-separated InGaN samples have inverted hexagonal pits which are formed by the In segregation on the surfaces. Room temperatures cathodoluminescence and imags at wavelengths corresponding to the GaN band edge, the In-poor and In rich regions were studied. It was shown that phase separated In-rich regions formed at the periphery of the hexagonal pits.

A deep level with the activation energy around 0.45-0.6 eV has persistently appeared in GaN samples grown by hydride vapor-phase epitaxy, organometallic vapor-phase epitaxy and molecular beam epitaxy. However, the origin of this deep level still remains unclear. In this study, we investigated this deep level trap E2 of GaN films by using deep level transient spectroscopy. The GaN films were grown by a conventional low pressure organometallic vapor-phase epitaxy technique with different V/III ratios. Frequency-dependent capacitance measurement was performed to determine the most proper frequency for capacitance measurements. Capacitance- voltage measurements were then applied to obtain the carrier concentrations. The carrier concentration became higher as the flow rate of NH3 got lower. The deep level E2 is found in GaN samples grown with higher V/III ratios. The trap concentration of level E2 increased with increasing NH₃ flow rate. Compared with the theoretical prediction of the nitrogen antisite level in GaN, the level E2 was believed to be related to nitrogen antisites.

We report the results of the investigation of the structural, surface morphological, and optical properties of GaN films grown by hydride vapor phase epitaxy. These films were grown on sapphire substrate with no intentional dopings. These as-grown GaN film samples with thickness ranging from 5.58 micrometers to 14.9 micrometers were investigated under room temperature conditions. The surface morphology of these films was investigated using an atomic force microscopy (AFM). The root mean square values of surface roughness range from 0.281 nm to 0.133 nm. The thicker films show lower defect counts with defect density of about 2 X 10⁸ cm^-2. The structural property of these films was measured by double crystal x-ray diffraction. The full width at half maximum of x-ray diffraction angle decreases as the film thickness increases with a lowest FWHM of about 265.5 arcsec. The optical properties of these films were investigated by photoluminescence measurement at room temperature. The result show a dominant near band-edge UV emission peak that increases with the film thickness with very weak yellow emission band.

A comparative study on GaN/sapphire has been performed by transmission electron microscopy (TEM) and IR reflectance (IR). TEM observations reveal that both the undoped and Si doped GaN epilayers have large density of threading dislocations. Dislocations in the undoped GaN tend to from open core structure, while dislocation lines in the Si-doped GaN are very sharp and the strain contrast is much more confirmed. It is believed that Si-doping causes the increase in undoped GaN to much more confirmed dislocation lines. Frank dislocation loops are also found lined up at a depth of about 110 +/- 10 nm from the interface. High resolution TEM study also reveals that the GaN buffer layer grown at low temperature has transformed into its thermodynamically stable wurtzite structure during the high temperature post- buffer GaN epilayer growth process. The comparative IR reflectance hows the corresponding behavior. The interference fringes of the Si doped sample, compared with the undoped ones, shows a contrast damping and reflectance reduction behavior, suggesting the presence of a transition/defect layers near the interface.

Optically pumped surface emitting and edge emitting stimulated emission behaviors in organic semiconductors was demonstrated in this study. For the surface emitting device, the microcavity was formed by sandwiching a polymer film containing PVK, Alq and DCM between a DBR with a reflectivity of 99.5 percent and a silver film. The sample was optically pumped by the three harmonic of a observed in DCM-doped PVK microcavity when pumped above the threshold intensity of 0.25MW/cm². The full width at half maximum was 0.6 nm with the peak wavelength at 603nm. For the edge emitting device, a laser dye DCM doped Alq matrix wa used as the gain medium. The sample was transversely pumped by the three harmonic output of the mode-locked Nd:YAG laser. The change of the emission spectra showed a clear threshold action and gain narrowing phenomenon when increasing the excitation intensity. The spectra narrowing observe result from the amplified spontaneous emission in the gain material.

We have designed a ne type of folding suspended polysilicon micro-mirror, integrating a new type of precision position- lock, a new compact design for the hinges and a bi- directional electrostatic actuator to bias the position of the mirror. The mirror is intended to be used in a very short external cavity laser configuration for acceleration/displacement sensing. An extensive theory has been built to guide the design and the fabrication of the sensor.

Torsion micromirror devices have been widely used in many applications. This paper describes the modeling of a torsion beam micromirror based on the parallel plate capacitor model. First, a generalized and normalized equation that governs the static characteristics of the torsion micromirror device is derived. Henceforth the influence of the structural parameters of micromirror is discussed, and the snap-down effect and the capacitance variation of the micromirror are studied. Finally, a micromirror is designed and fabricated. However, the model has not yet been verified by experimental data as testing is in progress.

In this paper, a new method for actuating micro-mirrors, which utilizes bending of the micro-mirror plate, was proposed in order to increase the rotational angle without increasing the sacrificial layer thickness. The analytical model of the proposed actuating method was established and, based on the analytical model, the expected micro-mirror operation is presented. In order to confirm the expected operation surface-micromachined polysilicon micro-mirror operation is presented. In order to confirm the expected operation surface micromachined polysilicon micro-mirror was fabricated and tested. The bending of the micro-mirror plate, however, was not observed in the experiment with the fabricated micro-mirror. There are two possible reasons for this. One is the driving force reduction due to the decreasing of the voltage difference between the micro- mirror plate and underlying electrode caused by electrical conducting between the two. The other is the non-optimized design in the mechanical structure which caused the bending of the supporting beam before the plate starts to bend.

In this paper, a high performance CMOS readout structure is proposed and applied for surface micromachined bolometer arrays. The silicon readout circuit is an important interface circuit for detector array and signal processing stages in the IR image syste. Conventional readout configurations for thermal resistive sensors can be classified into four groups (1) Constant Temperature (CT), (2) Constant Current (CC), (3) Constant Voltage (CV), (4) Constant Bias (CB). To achieve a high performance readout and fit the working characteristics of IR detector material, new CMOS readout structures have been developed and fabricated. Based on the application of the proposed CC input biasing technique, a new CMOS Bandgap Reference Constant Current readout structure is proposed and analyzed. The low power CMOS readout circuit is achieved using the reset switch techniques. By applying the proposed bias technique to improve low power, high linearity and low sensitivity of the resistive bolometer detectors and high performance readout interface circuit for the IR linear array is realized with a pixel size of 50 X 50 micrometers ².

In this paper we discuss crystal growth, spontaneous emission characteristics and low threshold performance of 1.3 micrometers InGaAs/GaAs quantum dot heterostructure lasers grown using sub-monolayer depositions of In, Ga, and As. Oxide-confinement is effective in obtaining a low threshold current of 1.2 mA and threshold current density of 19 A/cm² under continuous-wave room-temperature operation. At 4 K a remarkably low threshold current density of 6 A/cm² is obtained. We also discuss ground state lasing at (lambda) equals 1.07 micrometers of a vertical cavity surface emitting laser in which a stacked and high dot density active region has been incorporated. The high QD density active region is achieved using alternating monolayers of InAs and GaAs. Lasing threshold conditions and gain parameters for a ground state quantum dot vertical cavity laser are also analyzed.

GaAs/AlGaAs quantum dot arrays with different dot sizes made by different fabrication processes were studied in this work. In comparison with the reference quantum well, photoluminescence (PL) spectra from the samples at low temperature have demonstrated that PL peak positions shift to higher energy side due to quantization confinement effects and the blue-shift increases with decreasing dot size, PL linewidths are broadened and intensities are much reduced. It is also found that wet chemical etching after reactive ion etching can improve optical properties of the quantum dot arrays.

It is fairly well established that self-aligned quantum dots can form in strained epitaxial systems. One system that has been studied extensively is the InAs/GaAs system wherein the difference in lattice parameter is about 7 percent. Strains within the dot and the surroundings are known to influence the optical properties of the system. However, very little information is available on the strains in these quantum dots. In particular, the effect of shape of the initial shape of quantum dots and boundary conditions are not very well known. Strains in InAs quantum dots embedded in GaAs have been examined using the finite element method within a thermo-mechanical framework. The initial shape of the dot is assumed to be conical in 3D with different width/height ratio typical of quantum dots. Modeling is accomplished using a 2D axi-symmetric finite element model. Results of the simulation show that initially conical shaped dots become more rounded in shape and become lens-shaped. It has been shown that the width/height ratio is critical in determining the strains within the quantum dots. Results of the calculation are compared with the results of other calculations and experimental measurements of strains using the STM.

Quantum well intermixing (QWI) is a promising technology for the fabrication of photonic integrated circuits (PICs). In this paper, we report the development of a new QWI process using undoped and Er-doped SiO₂ dielectric caps prepared using sol-gel technique. A differential bandgap shift of as large as 83meV have been observed from samples intermixed with Er-doped SiO₂ respectively. Broad area gain guided lasers have been fabricated from the as-grown and samples with bandgap tuned to different degrees using undoped and Er-doped SiO₂. Lasers fabricated from the as-grown, undoped and Er-doped SiO₂ samples showed lasing wavelengths of 865nm, 850nm and 835nm respectively. Compared to the 865nm, the threshold current of the 850nm and 835nm wavelength lasers were found to increase by 5 percent and 9.5 percent respectively. The slope efficiencies from these lasers were found to exhibit only small change compared to the as-grown lasers. These results imply that the quality of the material remains relatively high after intermixed using sol-gel SiO₂ induced QWI technique.

Neutral impurity induced quantum well intermixing (QWI) is an attractive and promising postgrowth bandgap engineering process for the fabrication of photonic integrated circuits (PICs), as it introduces no additional electrical active dopants into the material system after intermixing. Here, we report the development of neutral impurity induced QWI processes in InGaAs-InGaAsP laser structure using low energy, i.e. 360keV, arsenic and phosphorous ion implantation. The samples were implanted at room temperature and 200 degrees C, with a dose range between 10¹² and 10¹⁴ ions/cm². The QWI stage was carried out by annealing the implanted samples at 650 degrees C for 120 s. Samples implanted at 200 degrees C give higher degree of QWI. Compared to P implanted samples, larger bandgap shift was observed form As implanted samples after annealing. A differential PL bandgap shift as large as 93 nm was observed from samples implanted with 10¹⁴ ions/cm² of As. Bandgap tuned lasers fabricate from intermixed sample; the current threshold density of the intermixed lasers slowly increases with the amount of blueshift and is kept below 20 percent for the most blueshifted devices. The attractive device characteristics of the bandgap tuned lasers show that damage induced by the ion implantation can be almost fully tread after annealing. This implies that the material remains in good quality after QWI.

In order to clarify the temperature dependence of the polariton phase change under electric field, an interferometric measurement was performed. The sample was a 400-micrometers -long polariton waveguide made of GaAs/AlGaAs layers with a p-i-n structure. A 7.5 nm GaAs single-quantum well is formed at the center of the core layer. The measured phase change at a lower temperature is about 10 times larger than that at a higher temperature, and the critical temperature is around 120 K. This critical temperature is remarkably high although the damping of the polariton usually occurs at a relatively low temperature. Such a high critical temperature indicates a possibility of a polariton device operation in a relatively high-temperature region.

We report the fabrication and characterization of the n-type InGaAlAs/InAlAs multiple quantum well structures, lattice- matched to InP, for the long wavelength IR detection. It is found that strong absorption resulted from the intersubband transition in the quaternary material is observable and the wavelength of the absorption varies with the well width while the barrier width is kept unchanged. Our experimental result are in good agreement with the theoretical estimation based on simple finite barrier model and can be confirmed by the photoluminescence data.

Photoluminescence (PL) spectroscopy and carrier lifetime measurement has been used to characterize optical properties of defects in the low-temperature (LT) grown GaAs/AlGaAs multiple quantum well structures. Two sets of samples were grown at 400 degrees C by molecular beam epitaxy on nominal and miscut towards GaAs substrates, respectively. After growth, samples were subjected to 30 s rapid thermal annealing at 600-800 degrees C. It is found that after annealing, two defect-related PL features appear in the samples grown on miscut GaAs substrates, but not in those grown on nominal GaAs substrates. The carrier lifetimes are about 31 and 5 ps in as-grown on nominal and miscut GaAs substrates, respectively. Optical transient current spectroscopy show different types of deep levels and their dependence on the annealing temperature. We found larger excitonic electroabsorption and stronger photorefractive effect in samples grown on miscut substrates.

In this paper a rigorous quantum mechanical multi-valley model is developed to assess the optical equivalent of the electrical Gunn effect: a laser beam pumps free electrons from the central conduction band valley of n-doped bulk GaAs towards its satellite values. The computational complexities involve a central fully nonparabolic degenerated (Gamma) - valley, an anisotropic L-valley of arbitrary degeneracy, impurity assisted, thermal and hot polar optical phonon assisted intravalley absorption mechanisms, and intervalley phonon assisted equivalent and nonequivalent intervalley absorption mechanisms. The influences of the doping concentrations, electron temperature, optical power density and the equivalent LL-intervalley deformation potential (IDP) on the magnitude and relaxation time of the optical Gunn effect are discussed and compared with experimental results. We found that the optically induced nonlinear absorption and intervalley transfer strongly depend on the equivalent LL-IDP. The large scattering on the available data for LL-IDP leads to large variations in the theoretical estimations. Under optical plasma resonance conditions we find an energy relaxation time in the L-valley of about 0.3 to 2.2 ps, a nonlinear refractive index n₂ of about 2.7 to 3.75 X 10^-81 cm²/W and e.g. a 10 percent electron transfer of about 1.8 to 3.2 MWcm^-2.

We have designed, fabricated and demonstrated ultra-compact directional couplers and 'race track' micro-resonators as nano-photonic building blocks for a range of WDM devices, including ultra-compact directional couplers, channel- dropping filters, 1 X N demultiplexers and 2 X 2 crossbar switches.

We have successfully fabricated optically pumped semiconductor micro-disk and micro-ring lasers under the InGaAsP/InGaAs system at the 1.5 micrometers wavelength and under the InGaP/InGaAlP system at the 0.66 micrometers wavelength. The spontaneous emission factor (beta) of these micro-lasers is estimated directly from their output-pump curves and its dependence on the cavity volume is verified. Interesting phenomena regarding the far-field emission pattern and lasing linewidth of these micro-cavity lasers are experimentally observed and theoretically studied.

In_0.22Ga_0.78N/In_0.06N multiple quantum well (MQW) microdisks with a size of 5.6 micrometers in diameter have been fabricated by photolithography and ion beam etching. Time-resolved photoluminescence (PL) has been employed to study optical transitions in MQW structure and microdisk. The dominant emission from both MQW structures and microdisks were from localized exciton transitions. It was found in the microdisks that the low energy shoulder of the PL spectrum was quenched, and that the spontaneous emission line width was narrower while its intensity was enhanced with respect to that of the MQWs, which may be related to microcavity effects in the microdisks. A blue shift of the PL peak from the MQW microdisks compared with that in the MQW structures was also observed, and can be understood in terms of a reduced piezoelectric field due to strain relief in the microdisks. Microdisks with grating patterned micro- couplers around the disks edges were also fabricated by e- beam lithography to enhance light extraction from the microdisks. Near-field scanning optical microscopy was employed to make the near-field fluorescence images of the microdisks, which showed a strong emission preference in certain directions. The potential applications of III- nitride microdisks for optical interconnects and integration are also discussed.

OPtical microdisk is based on circularly symmetric micro- resonator and featured of the 'whispering-galley' modes with high quality of factor Q. However, the non-preferred directional emission and lack of high output from the disk are its drawbacks for application. Recently, a remarkable advance in the novel deformed microdisk laser at middle-IR wavelength is highly attractive. In this report, as a preliminary try for microdisk at visible range, the InGaAlP quantum well circular cylindrical and deformed microdisks with radii about 2.5 to 10 micrometers emitting at wavelength of 0.62-0.67 micrometers were prepared by electron beam lithography and wet etching processing etc. The optical emission properties of these microdisks and studied by employing the scanning electron microscopy, atomic force microscopy, fluorescence image microspace and scanning near-field optical microscopy etc. The preferential emission in these deformed microdisks was visually observed. When the cross section of microdisk was gradually deformed from circle, the change of fluorescence image from uniform ring towards 2 or 4 favorable emission along the circumference of microdisks was confirmed. The deformation could be caused by either the shape or etching profile of the disk waveguide. In addition, the microdisks patterned with some microstructures were proposed.

We analyze the mode behaviors for semiconductor lasers with an equilateral triangle resonator by deriving the mode field distribution and the eigenvalue equation. The eigenvalue equation shows that the longitudinal model wavelength interval is equivalent to that of a Fabry-Perot cavity with the cavity length of 1.5a, where a is the side length of the equilateral triangle resonator. The transverse waveguiding is equivalent to a strip waveguide with the width of (root)3 a/2, and the number of transverse modes supported by the resonator is limited by the total reflection condition on the sides of the equilateral triangle. Semiconductor microcavity laser with an equilateral triangle resonator is suitable to realize single mode operation, and the mode wavelength can be adjusted by changing the side length.

Photonic crystals an other photonic devices could be efficiently produced using relatively simple and cheap Plasma Focus Pinch x-ray point sources, similar to the NX2. With this point x-ray source, it was demonstrated that with a proximity printing scheme, feature sizes less than 100 nm could be reproduced in a 500 nm UV3 CAR layer.

3D photonic lattices are engineered 'materials' which are the photonic analogues of semiconductors. These structures were first proposed and demonstrated in the mid-to-late 1980's. However, due to fabrication difficulties, lattices active in the IR are only just emerging. A variety of structures and fabrication approaches have been investigated. The most promising approach for many potential applications is a diamond-like structure fabricated using silicon microprocessing techniques. This approach has enabled the fabrication of 3D silicon photonic lattices active in the IR. The structures display bandgaps centered from 12(mu) down to 1.55(mu) , depending on pitch.

A relatively simple technique for fabrication of GaAs-based quasi-3D photonic crystals has been investigated. Selective impurity-induced layer disordering and wet oxidation techniques are utilized. The feasibility of this technique is successfully demonstrated and a photonic bandgap material with its bandgap around 1.18 micrometers has been fabricated. The electro-optic coefficients have been measured for the first time in such a medium. The process is reproducible an lends itself to integration with other optoelectronic and electronic devices on the same substrate, which might be required for pumping, electrical injection or other functions.

2D hexagonal lattice photonic crystal made of superconducting rods embedded in dielectric matrix and dielectric rods embedded in superconducting matrix are studied. We used two-fluid mode to describe the electromagnetic response of the superconductor phase. The superconductor-dielectric photonic band structures are computed using the plane wave expansion method. We found an extremely large low frequency gap as due to the electric field expulsion in the superconductor. Qualitative explanations for the dependency low frequency gap size on dielectric constant, penetration depth and filling fraction are given. A smaller gap has been found at much higher lattice constant/wavelength ratio. We also found a fundamental mode with extremely localized electric field in the dielectric phase, similar to the localized mode in defective photonic crystal. This photonic crystal could be useful for superhigh-Q periodic resonant cavities.

Gigabit/s-LANs with 0.85 micrometers vertical cavity surface emitting lasers (VCSELs) are now going into the market. But, their link length is limited to be shorter than 500 m due to modal dispersion of employed multi-mode fibers and various modal problems should be considered in system design. The next step will be to develop long wavelength VCSELs matching to a single model fiber with longer link lengths of several km and higher data rates. Long wavelength single mode fiber datacom should be advantageous because of avoiding modal noise and relaxing eye safe issues. Recently, we demonstrated a 1.2 micrometers wavelength highly strained GaInAs/GaAs quantum well edge emitting laser, which exhibits reasonably low threshold and excellent temperature characteristics. The threshold current is as low as 13 mA for an as-cleaved 5 X 380 micrometers laser. A characteristic temperature T₀ under pulsed operating is as high as 140 K. This is the record high T₀ in 1.2-1.3 micrometers wavelength band. Even under 'heatsink-free' cw operations, T₀ was much higher than that of conventional 1.3 micrometers GaInAsP/InP systems. We can avoid thermoelectric coolers as well as heatsink itself, thus, an all-plastic mold package without heatsink may give us a drastic cost reduction. It is interesting to note than commercial standard single mode fibers are designed to locate a cut-off wavelength at around 1.2 micrometers for the purpose of production tolerance. A question arises: whether this 1.2 micrometers wavelength band can be utilized for single mode fiber datacom or not.We have demonstrated a 2 Gb/s-5km single mode fiber data transmission experiment using a fabricated 1.22 micrometers uncooled GaInAs/GaAs laser. We believe that the VCSEL technology may drastically improve the transmitter performances at this new wavelength band and this 1.2 micrometers Gigabit LAN may become realistic by extensive developments. In this paper, we would like to discuss a possibility of high speed datacom using a newly developed 1.2 micrometers highly strained GaInAs/GaAs lasers.

This paper examines the performance of a serial-search synchronization system in the presence of multiple access interference and receiver noise for a non-coherent fiber- based optical CDMA system using optically orthogonal codes. The synchronization performance of two different optical CDMA system, an on-off keyed system and an M-ary pulse- position modulation system with M equals 2, are compared. The effects of the dwell-time, the total number of users, the code weight, decision threshold and optical hard-limiters on the mean acquisition time of the synchronizer are examined. It is shown that an optimum dwell-time exist which minimizes the mean acquisition time.

In this paper the direct spreading/wavelength hopping en- /de-coding scheme for optical code-division multiple access is proposed. The system structure is designed and analyzed. A new code sequence-wavelength hopping extended quadratic congruence for prime code is adopted. It is shown that the code capability can be increased by increasing the number of discrete wavelengths or by employing asymmetric system with different prime numbers for spreading and hopping. The synchronous signal is designed and analyzed. It is very easy for user to decode synchronously. The performance of the system is investigated and it is shown that the en-/de- coding scheme and system structure are feasible.

All-optical time-domain demultiplexers are expected to play a major role in future ultrafast all-optical time division multiplexing systems to overcome the electronic bottleneck. Ultrafast nonlinear interferometer (UNI) is a good candidate for all-optical time-division demultiplexing. The switching efficiency of UNI is investigated numerically. We construct an analysis model of the UNI. In our analysis, the effects of control pulse parameters such as pulsewidth, power and jitter on the switching efficiency of UNI are considered. The required peak power of the control pulse to obtain maximum switching efficiency is found to decrease in as the width of the control pulse is increased. Jitter of control pulse reduces the switching efficiency. It is also noticed that the length of birefringent fiber is no contribution to the switching efficiency. However, more than 90 percent switching efficiency could be reached when the control pulsewidth varied 40 percent, when pulse power is in 40 percent or when the jitter is about 3 percent.

In this paper the new progress in the researching fields of optical switch were reviewed. A compute model for calculating the switch speed, extinction ratio, noise figure, dynamic range as well as the switch gain was presented. The switch time, contrast ratio of SOA gate are calculated and evaluated. The methods to suppress the ASE noise are discussed. A novel and special method to extract optical route signal is presented. The result of the theoretical analysis showed that the optical gain of the SOA should be setup in optimum so as to obtain the best performances of the switch. An optical switch matrix using the polarization-insensitive strained quantum well SOAs and the optical couplers was fabricated and a novel and simplified method for extracting the logical control signal of the optical switch was specially designed, in which the optoelectronic integrated circuit (OEIC) techniques could be used to fabricate a compact, effect, high speed and low-cost optical switch matrix. IT is show that with the rapid improvement of OEIC techniques, the larger scale switch matrix based on SOA gate would be able to get into practice in the near future.

A normal-incident SiGe/Si multiple quantum wells photodetector was reported. The structure and fabrication process of the photodetector were introduced. The photocurrent spectra measurement showed that the response spectra was expanded to 1.3 micrometers wavelength. The quantum efficiency of the photodetector was 0.1 percent at 1.3 micrometers and 20 percent at 0.95 micrometers .

Origin of erbium luminescence at 1.54 micrometers , a prospective optical source in silicon based optoelectronics has been analyzed. Erbium atoms in silicon have been considered as recombination centers with specific values of capture and emission coefficients. Electron-hole recombination through these levels has been considered to be the origin of erbium excitation. At steady state of excitation, a certain fraction of erbium sites were found to remain occupied by electrons. Trapped electrons, which eventually recombine with holes in the valence band, provide the energy for (formula available in paper)yields (formula available in paper) transition of erbium atoms. It was however found that, even with 100 percent quantum efficiency of this energy transmission, not every electron- hole recombination corresponds to the excitation of an erbium atom. This wastage of recombination energy was attributed to the rather long lifetime of erbium decay. Capture and emission processes of photo generated excess carriers in the erbium related level have been equated for non-steady conditions. It has been shown that the steady state erbium luminescence actually follows a transient rise, typically of the order of few hundred microseconds. The anomalous behavior of continuous rise of erbium luminescence after termination of short excitation pulses of 30 μs microsecond has been explained mathematically for the first time.

In optical computation matrix multiplication takes an important role for the purpose of digital data processing. Lot of proposals with various techniques on matrix-matrix multiplication have been seen in the last few decades. Here in this communication the authors propose a new concept of digital matrix multiplication scheme with fiber optic spatial maps.

ONe of the interesting applications of 2D VCSEL arrays is high density optical data storage. We proposed a micro-metal aperture VCSEL for producing optical near-field. The evanescent wave emitted from a small metal aperture formed on a VCSEL surface is irradiated to an optical disk, such as a phase change optical disk. We carried out a near-field analysis on the radiation from the metal micro aperture loaded on a VCSEL by using 2D finite element method (FEM), showing a possibility of a spot size of below 100 nm. We can recycle the reflected wave from the metal aperture, when we properly design the phase matching between the DBR mirror and the metal. We can expect an improvement in a power conversion efficiency of radiating near field light from the aperture by using a 'photon recycling' effect. An expected efficiency and power density are discussed for 850 nm metal aperture VCSELs. We have fabricated micro-metal aperture VCSELs by using focus ion beam etching. The size of the fabricated apertures ranges from 100 nm and 400 nm. We have realized sub-mA low threshold metal aperture VCSELs. The power density is estimated to be approximately 6 kW/cm². We will be able to improve the power density by reducing the oxide aperture in the cavity. We also discuss on another way to increase the efficiency and the power density, such as using a surface plasmon effect of a small metal tip formed on the surface. We will discuss a possibility of optical near-field recording by using the proposed metal aperture VCSEL.

The diffraction efficiency of volume grating written by two- wave mixing in Ce:KNSBN photorefractive crystal as a function of the writing beam ratio for different polarized reading beam is experimentally studied. It is found that, the polarization and the incident direction of the reading beam strongly affect the diffraction efficiency. In the selected direction, the extraordinarily polarized reading beam obtains enhanced diffraction and achieves nearly fifteen times larger diffraction efficiency than the ordinarily polarized reading beam. The modified coupled-wave theory is used to fit the experimental data and the fitting result are coincident with the experimental result. We also theoretically examined the realization between the diffraction efficiency and the amplitude coupling constant k of the reading beam and its diffracted beam. As k < 6cm^-1, the diffraction efficiency has single maximum and the maximum diffraction efficiency increases as k increases. As k > 6cm^-1, the diffraction efficiency curves exhibit two peaks. But the central position of the curves does not change with the variation of k.

The characteristic of embossed information is very important for magneto otpical disk, which is used by the magneto optical driver to control the axial focusing and radial tracking servos on the information tracks and to search the sectors. It must be tested in the process of development and production of magneto otpical disk. the characteristics of 4X-density magneto otpical disk's embossed information are described in this thesis; the test method of the header signal and groove signal is discussed based on the international standard test condition. A test system has ben designed which can measure the characteristics of embossed information of magneto optical disk, and a sample disk's test result is given in the end.

Main application of 650nm band laser diodes are for digital versatile disk (DVD). We demonstrate here the 650nm AlGaInP LD grown by LP-MOCVD with the structure of selected buried ridge waveguide. Excellent performance of LD have been achieved such as threshold current, threshold current density as low as 20mA and 350A/cm² respectively at room temperature, the operating temperature up to 90 for the linear power output of 5mw. RIN is about -130db/Hz, the samples of LD have been certified by PUH manufacturers.

We present an investigation of third-order optical nonlinearity in surface modified PbS and Cd_xPb_1-xS nanoparticles using the Z-scan technique with femtosecond laser pulses at 780-nm wavelength. The samples include PbS nanoparticles in microemulsion with PbS concentration range from 0.3-2.5 X 10^-3 M and Cd_xPb_1-xS nanoparticles in microemulsion with x from 0 to 1. An extended Z-scan theory based on the Huygens- Fresnel princeps is employed to extract the nonlinear refraction index from the experimental Z-scan data with a large nonlinear phase shift. The nonlinear refractive index in PbS nanoparticle microemulsion is found to increase linearly with PbS concentration between 0.3 X 10^-3 and 1.9 X 10^-3 M. The highest concentration microemulsion gives a nonlinear refractive index of 1.8 X 10^-11 cm²/W, which is approximately 4 orders of magnitude higher than those of commercially available bulk semiconductors, such as ZnS and CdS, measured at the same conditions. In Cd_xPb_1-xS nanoparticles, Cd_0.33Pb_0.67S exhibits relatively larger refractive nonlinearity. For all samples, nonlinear absorption remained unmeasureable up to 0.9 GW/cm². The observed large refractive nonlinearity in these nanoparticles may mainly be attributed to the optical Stark effect and contribution from the surface-trapped states in the nanoparticles.

Abstract not available.

Using a new method for measuring photorefractive two-wave mixing gain, we present the first experimental demonstration of nonreciprocal energy transfer during two-wave mixing under an external magnetic field. The nonreciprocal energy transfer is observed with mixing gains approaching 164 cm^-1 exhibiting the characters of nonlinearity and saturation. A simple model of negative differential mobility and ultra fast carriers lifetime was proposed to explain these results.

The stability of soliton propagation in a system with spectral filtering, linear and nonlinear gain is numerically investigated. Different types of analytical solutions of the cubic complex Ginzburg-Landau equation, namely solutions with fixed amplitude and solutions with arbitrary amplitude, are presented. Then, the evolution equation is solved numerically assuming various input waveforms. Our results show that it will be possible to achieve relatively stable pulse propagation over long distances by the use of suitable combination of linear and nonlinear gains. However, truly stable propagation of arbitrary amplitude solitons can be achieved only in a system with purely nonlinear gain. A new soliton compression effect is demonstrated both for fixed- amplitude and arbitrary-amplitude solitons.

Nonlinear absorption, 1D self-focusing and 1D self-trapping of optical beams are studied in 150 ppm Fe-doped Bi₁₂SiO₂₀ crystal using single beam Z-scan technique in nano second regime using coherent and incoherent laser pluses with out applying any external electric field across the crystal. When the crystal is placed in expanding beam 1D self-trapping is observed due to 1D self-focusing. The nonlinear absorption is also observed at high intensities due to trap assisted excited state absorption as well as two photon absorption. The ground state absorption and increased nonlinear absorption at 532 nm and 595 nm compared to pure BSO indicates the increased impurity traps in the crystal lattice due to iron incorporation. The studies reveal that incorporation of iron in BSO making it an excellent optical limiter.

Amorphous silicon-carbon-nitrogen films prepared using the industry-used electron cyclotron resonance chemical vapor deposition technique at room temperature for photoconductive detectors are systematically investigate.d It is found that the film quality is sensitive to the preparation conditions. The deposition rate of the films is found to increase with the microwave power. It peaks at a ratio of silane to the mixture of silane, methane and nitrogen around 33 percent and at a radio frequency (RF) bias of 100 V. The otpical energy band-gap of the films increases monotonically with the gas ratio but decreases with RF bias. The conductivity of the materials is also found to vary with the preparation conditions. The change in the energy band-gap and conductivity is associated with the change in the incorporation of carbon and nitrogen. The wavelength in the range of 0.65 to 0.45 micron could be detected by controlling the deposition conditions.

It has been studied the selective InGaAs quantum dots growth on laser-patterned GaAs substrate by atmospheric pressure metal organic chemical vapor deposition. We have patterned the samples below etching threshold power density 8.84 MW/cm² by argon ion laser. The depth and lateral size of the pattern are about 8 nm and 100 nm, respectively. The QDs were grown on AlGaAs matrix.

In this paper, the optimization and application results of SU-8 are reported. SU-8 is an ultra-thick, negative, epoxy- type, near UV photoresist based on EPON SU-8 resins from Microchem Corp. SU-8 is a highly photosensitive resist and its properties are greatly affected by the process parameters. The parameters, which have influence on the properties, were optimized by three level, L9 Orthogonal Array of Taguchi Method. Two kinds of photoresists, SU-8 and SU-8 50, and four parameters such as the prebake time, postbake time, exposure time and developing time were chosen to optimize. We found that there exist some minor differences between out result and the published data. This different could be due to either the EPON SU-8 content or the fabrication conditions. According to the optimized data, for SU-8 and SU-8 50, many microstructures with thickness more than 100, 500 micrometers and aspect ratio more than 20, 50 were obtained, respectively. All these were achieve without the introduction of GPL, a stronger developing solution. The positive photoresists AZ9260 with thickness more than 20 micron were patterned as the sacrificial layer. Using SU-8 as the structural layer, we fabricated some micro-components such as micro-cantilevers, microchannels and micro- heatpipes. The primary experiments demonstrated that SU-8 could be used as the structural material for micro- components and even for some MicroElectroMechanical Systems.

The reason for the instability of passively Q-switched lasers has been analyzed. Based on those reason is a novel model named pre-pumping passively Q switching is presented. The model we developed accounts for the properties of the lasing material, the saturable absorber, the pumping power and the resonator. With the aid of new factor f_p, we calculate the effects of pre-pumping mechanism on the pulse output energy. Like the model of Guohua Xiao the express we derived can be used to optimize the laser's performance.

In order to improve the stability of passively Q-switched lasers we put forward a kind of pre-pumping mechanism. Based on this mechanism we deduce an analytical expression which can be used to calculate or optimize the important parameters of passively Q-switched lasers. The analytical expression has been discussed in detail and the results can also be used in many cases of passively Q-switched lasers.

Based on the growth process analysis of nanocrystalline silicon films, a fractal growth model named diffusion and reaction limited aggregation (DRLA) model is proposed, which is different from diffusion limited aggregation model. Nanocrystalline silicon films with quantum scale structures were prepared by PECVD method. Computer simulation of the DRLA model has been done, the results are in agreement with the experimental results. The relationship between structure of nanocrystalline silicon film and aggregation of nanocrystalline silicon film has also been discussed.

In₂O₃ and Fe₂O₃ were doped in LiNbO₃ and Czochralski method was used to grow In:Fe:LiNbO₃ crystals. The light scattering ability resistance, exponential gain coefficient, diffraction efficiency and response time of the crystals were measured. The light scattering ability resistance and response time of In:Fe:LiNbO₃ is one magnitude higher than Fe:LiNbO₃. In:Fe:LiNbO₃ was used as storage element to make the large capacity holographic storage and the holographic associative storage reality. The excellent results were gained.

Wide applications of lasers have stimulated a great interest in development of optical limiting devices. These devices can be used to protect optical sensor form laser-induced damage because their transmission is high when they are exposed to low-power laser light, and their transmission becomes low when irradiated by intense laser beams. Here we report such a device based on nonlinear optical effects in two neutral nickel complexes with multi-sulfur 1,2 dithiolene ligands, 1 and 2. The limiting device consisted of a focusing setup and a 1-mm-thick cell, which contained a benzene solution of one of the complexes. THe limiting properties were investigated by both nanosecond and picosecond laser pulses. At 532 nm, the limiting thresholds of complexes 1 and 2 measured by the picosecond laser pulses. At 532 nm, the limiting threshold of complexes 1 and 2 measured by the picosecond laser pluses with a focusing geometry were determined to be approximately 0.3 J/cm². The linear absorption spectra of the to complexes also indicated that their limiting response should cover the visible and near-IR region. All these result show their limiting performance is superior to the limiting effecting C₆₀. Picosecond time-resolved pump-probe and Z-scan experiments revealed that the observed limiting effects should originate from excited-state absorption and refraction.

Optical limiting effects in cubane-like metal clusters dissolved in dichlormethane have been studied by measurements of nonlinear transmissions, nonlinear scattering, and pump-probe. The nonlinear transmission measurements show that there are strong optical limiting effects in these two cluster solutions; and the silver- containing cluster has larger limiting properties than the other. The nonlinear scattering results indicate that nonlinear scattering is responsible for the limiting action in both clusters. And the pump-probe experiments show that the nonlinear scattering is thermal in origin.

In this paper, we present the laser induced fluorescence spectra and the time-resolved spectra of the A³ (Pi) ₀yields(Chi) ¹(Sigma) ⁺ and C¹(Pi) ¹(Sigma) ⁺ for InCl molecule in the ranges of 266.5-287.0nm and 332.0-373.0nm. It is the first time those radiative lifetimes of the C¹(Pi) ₁ and B³(Pi) ₁ states have been measured by laser-induced fluorescence. From the time-resolved spectra under different pressures, we obtained the collision-free radiative lifetimes and quenching rate constants for InCl molecule: A³(Pi) ₀, 370ns, 9.87 X 10^-11 cm³molec^-1s^-1; B³(Pi) ₁, 353ns, 1.985 X 10^-10cm³molec^-1s^-1, 11ns. From the radiative lifetime and the Frank-Condon factors q_v'v'' for the v'-v'' transitions, the electronic transition moments re² of B³(Pi) ₁ and C¹(Pi) ₁ states have been obtained.

This paper deals with the assay requirements and the method of plane. Wave quantity of the plate working surface according to the National Standards of 'cast iron plate' and 'rock plate', derives in detail, the detecting principle of plane wave detector and gives out the relationship between the partial plane error and the partial defect of the plate and the plane wave quantity. It also inquires into the relationship between the contact spot and 200 mm straight line wave and plane wave quantity.

Ultra high-speed streak cameras with image converter tubes play a very important role in the diagnosis of most experiments in laser fusion research. The window materials of the image converter tube usually applied borosilicale glass, but it is only transparent for visible light. In order to apply in VUV.UV.visible light region for the tube, we used MgF₂ window material in the tube and exhibits excellent performance on the photocathode sensitivity and spectral responses in the image converter tube.

The direction of this paper is to describe the analytical tools and measurement techniques used at SilkRoad to evaluate the optical and electrical signals used in Optical Refractive Synchronization for transporting SONET signals across the transmission fiber. Fundamentally, the direction of this paper is to provide an outline of how SilkRoad, Inc., transports a multiplicity of SONET signals across a distance of fiber > 100 Km without amplification or regeneration of the optical signal, i.e., one laser over one fiber. Test and measurement data are presented to reflect how the SilkRoad technique of Optical Refractive Synchronization is employed to provide a zero bit error rate for transmission of multiple OC-12 and OC-48 SONET signals that are sent over a fiber optical cable which is > 100Km. The recovery and transformation modules are described for the modification and transportation of these SONET signals.

The direction of this paper is to describe the experiments and analytical techniques used by SilkRoad, Inc. for sending 40 GHz of bandwidth, incorporating an eclectic body of data, over a single laser - single fiber over > 100Km of optical fiber using the same wavelength in both directions. The paper will outline the various basic tenets of Optical Refractive Synchronization and the subsequent use of Ellipsometric Phase, based on these tenets, that allows a compilation of CATV, voice, video and SONET data to be transported in both directions without interference between the otpical signals going in both directions over the single fiber. The second portion of the paper will describe the test setup and measurement techniques that were used to validate the analytical models. Pictures of the Spectrum Analyzer data and the subsequent recovery of the eclectic information is then provided for all of the signals that have been transported.

The 'optoelectronics industry' is a collection of six o more distinct industries that all depend on OE technology. The major markets are in communication, imaging, storage and displays. This paper gives a brief overview of the anticipated paradigm shifts, the potential markets and the promising new technologies in various OE markets.

The development of vertical-cavity surface -emitting lasers (VCSELs) has led to new types of low power, high efficiency light sources for data communication. The small size, low power, and surface-normal emission of VCSELs has enabled relatively dense 2D arrays for highly parallel data communication and optical signal processing. In this paper we examine the issues of device scaling on VCSEL performance. We look specifically at what benefits may be derived from continued scaling of the active volume down to minimum sized dimensions, and what device schemes may be required to obtain the dimensions, a significant improvement in modulation speed is predicted based on the radiative lifetime change due to the Purcell effect. However, several parasitic effects must be controlled in order to realize these benefits. Most important are control of the optical loss due to diffraction or scattering,and control of the electronic losses due to carrier diffusion and surface effects. Novel optical confinement schemes based on oxide- apertures, photonic bandgaps, and/or closely coupled 2D array may be useful for controlling optical loss, while self-assembled quantum dots are attractive for controlling electronic diffusion to dimensions within the minimum optical mode volume.

A microscopic many-body theory for the nonlinear optical response of semiconductors is reviewed. The importance of Coulomb interaction induced carrier correlations is demonstrated in excitonic pump-probe spectra. The influence of excitonic and biexcitonic contributions to coherent pump- induced absorption changes at the exciton frequency are discussed. Absorption changes induced by incoherent exciton and unbound electron-hole populations are studied.

This paper discusses the role and impact of advancements in Photonics Technology on the performance enhancement of guided missile weapon systems with specific reference to the development of Indian guided missiles program. India is emerging as a technologically strong nation with core competence in Space, Missile and Nuclear technologies, advanced computing including supercomputers and software. Based on the realization of the fact that high technology strength is the key to economic prosperity and military strength, India is progressing several high technology areas that help in attaining the global competitiveness. Photonics is identified as one of the important areas in this direction and hence high priority has been accorded for R and D in Photonics. This paper reviews the current trends and developments in missile technology and highlights some of the important developments in Photonics that have a force multiplying effect on the performance enhancement of guided missile systems.