The radiative recombination mechanism of InGaN single-quantum- well (SOW) blue light-emitting diodes (LEDs) and InGaN double heterostructure (DH) ultraviolet (UV) LEDs has extensively been investigated by means of the dependence of photoluminescence (PL) and time-resolved PL (TRPL) spectra on an external-electric field. Two emission components are found in the luminescence spectra from each LED on the condition of reverse-bias at 77 K. It is also found that the luminescence intensity of the LEDs decreases dramatically with increasing reverse-bias voltage at room temperature (RT). The model based on field ionization of excitons cannot explain the present experimental phenomena. It is therefore suggested that the free-carrier recombination process is dominant at RT. We have also suggested that these experimental results on the blue and UV LEDs can be explained by the same recombination model. Finally, on the basis of both the experimental ecidence in In_0.08Ga_0.92N epitaxial layers and strong electron-phonon interaction, the radiative recombination mechanism on In_xGa_1-xN ternary alloys has been discussed.

Bulk layers of GaAsN and InGaAsN and GaAs/InGaAsN/GaAs quantum wells with nitrogen concentration of about 1% have been grown by bas source molecular beam epitaxy with a radio frequency discharge N source. The material has been characterized by X-ray diffraction, secondary ion mass spectrometry, photoluminescence (PL) and Hall effect with the intention of understanding and overcoming the mechanism responsible for the diminished optical quality of the nitride material relative to the material without nitrogen. The PL yield of the InGaAsN quantum wells can be significantly improved by optimized annealing treatment, although the quality is currently still inferior to the nitrogen-free material. Hall effect measurements on the nitride material indicate the presence of states in the bandgap acting as hole traps and electron traps; it is expected that these states act as the non-radiative recombination centres responsible for the reduced optical quality.

Photoluminescence (PL) measurement and optical pumping at 25K were studied for high-indium-composition InGaN/GaN multiple quantum well (MQW) structures grown by low-pressure metalorganic chemical vapor deposition. The result show that thermal annealing can reduce the compositional fluctuation of indium content. The optical pumping spectra show 5 stimulated emission (SE) peaks. This phenomenon might be attributed to intersubband transition. The transition between quantized levels for each peak was precisely identified by solving the time-independent Schrodinger equation and finite-difference method. The ratio of conduction- band discontinuities to the valence-band discontinuities of InGaN/GaN QW, (delta) E_c:(delta) E_v=38:62, can be obtained.

In this work we have modeled the optical functions of hexagonal GaN (corresponding to E(perpendicular)c) in the range from 1 eV to 10 eV using a modified critical points model. The difference between the model employed and the standard critical points model is that the exponent m is an adjustable parameter, and does not have fixed value depending on the type of critical point. Excellent agreement with the experimental data has been achieved over the entire investigated spectral range. Obtained relative rms errors equal 0.6% for the real part, and 2.0% for the imaginary part of the index refraction.

A small indium flux was used as a surfactant during the growth of gallium nitride films by rf-plasma assisted molecular beam epitaxy. The effects of the indium surfactant on the optical and structural properties of undoped GaN were studied by photoluminescence spectroscopy, high-resolution X-ray diffraction, atomic force microscopy, Rutherford backscattering spectroscopy, and low-frequency noise. Photoluminescence spectra show that the GaN thin films grown in the presence of In surfactant exhibit supressed yellow luminescence compared to films grown under the same experimental conditions but without In surfactant. The X-ray rocking curves demonstrate a 20% decrease in the full width at half maximum value for the films grown with In surfactant. AFM studies show that the root mean squared roughness for films grown with and without In surfactant are 5.86 and 6.99 nm respectively, indicating significant improvement in surface morphology. RBS and ion channeling shows the presence of stacking faults and dislocations and GaN growth with In surfactant and stacking faults in GaN grown without In. For the characterization of defect properties in the films we conducted detailed studies of 1/f and Generation-Recombination (G-R) noise on our samples. About 65% reduction in the Hooge parameter was observed in the film grown with In surfactant, indicative of a corresponding reduction in defect states within the material. For f $GTR 500Hz, G-R noise was the dominating fluctuation process. Detailed characterization of the G-R noise over a wide range of temperatures enabled the determination of the energy levels of the traps responsible for the G-R noise. Three different trap levels were observed using noise measurement technique. For films grown without In surfactant, traps with activation energies 806 meV, 241 meV and 100 meV were observed, whereas for samples grown with In surfactant traps were observed at 666 meV, 208 meV and 90 meV. Such systematic reduction in the energy levels of the traps may arise from the relaxation of strains in the material when grown under the application of In surfactant.

We have attempted the grown of GaN by RF-MBE which crystalline quality is a match for the by MOCVD, performing homoepitaxial growth using MOCVD-GaN as a substrate. We confirmed that homoepitaxial GaN had Ga polarity by (1 x 1) RHEED streaky pattern after coolingd own. 10 min-BHF-etching was the most effective for cleaning the surface of GaN substrate, and as the result crystalline quality of homoepitaxial GaN was improved. Thermal annealing of GaN substrate was also affect for the improvement of crystalline quality of homoepitaxial. From XRD measurement, FWHM of diffraction spectrum from homoepitaxial GaN almost equaled to that from GaN substrate. So, the crystalline quality of homoepitaxial GaN was not inferior to that of GaN substrate. Large compression strain in c plane of homoepitaxial GaN indicated that homoepitaxy prevented 3D growth and/or formation of defects. From PL measurement, we observed radiative recombination of free excitons clearly from homoepitaxial GaN.

The microstructural and luminescent properties of sputtered GaN thin films pre-irradiated and the (gamma) -ray irradiated were systematically investigated. Analytical results revealed that the increasing dose of (gamma) -rays could enhance the more occurrence of nitrogen vacancies which not only created a prominent deep level luminescence but also destroyed the crystallinity of GaN thin films. For lose dose of (gamma) -ray irradiation (4 Mrad (GaN)), evidence showed that by raising the irradiation dose, more associated Ga-H complexes will be effectively promoted, yielding an enhanced yellow bad emission. However for high dose of (gamma) -ray irradiation (4 Mrad (GaN)), further higher dose of (gamma) - rays could lead the dissociation of Ga-H complexes in GaN samples, resulting in a repressed yellow band emission.

Implementation of a novel high-density plasma configuration has led to high etch rates of various opto-electronic device structures. The etch rate for multiple quantum well GaN/GaInN structures exceeds 7500A/min, and that for AlGaInP/GaInP structure is over 4.5 micron/min with near-vertical profile. Discussion will cover the analysis of the etch-rate, micro- morphology, etch-profile and selectivity with respect to the influence by various process parameters. Deep-etch for over 20 microns with photoresist as the protection layer has been achieved, which resulted in nearly 90-degree profile.

Carrier dynamics in self-assembled quantum dots, grown by molecular beam epitaxy, have been studied. The temperature dependence of the relaxation times, measured by room temperature high frequency impedance response of quantum dot lasers and by low temperature (T=4K) differential transmission spectroscopy. strongly suggests that electronhole scattering is the dominant scattering mechanism in quantum dots. The favorable relaxation times can be exploited to realize far infrared emission and detection based on intersubband transitions in the dots.

Carrier dynamics in self-assembled quantum dots, grown by molecular beam epitaxy, have been studied. The temperature dependence of the relaxation times, measured by room temperature high frequency impedance response of quantum dot lasers and by low temperature (T=4K) differential transmission spectroscopy, strongly suggests that electron- hole scattering is the dominant scattering mechanism in quantum dots. The favorable relaxation times can be exploited to realize far infrared emission and detection based on intersubband transitions in the dots.

From a recent study of the growth and optical properties of quantum dots (QD's), we demonstrated that artificial atoms with sharp electronic shells can be fabricated with good control, using self-assembled QD's grown by molecular beam epitaxy. Size and shape engineering of the QD's during growth permits the tailoring of their intersublevel energy spacings. We demonstrate a much improved uniformity of the macroscopic ensembles of QD's, with well-resolved electronic shells. In addition to size and shape engineering of the QDS's in the case of single-layer samples, we demonstrate significant improvements in the uniformity of the vertically self-aligned stacked QD's. State-filling spectroscopy of the zero-dimensional transitions between confined electrons and holes demonstrates that the energy levels are readily tunable. One to five confined levels, with an inter-level energy spacing between 25 and 90 meV, are obtained by adjusting the growth temperature or with post-growth annealings. Such QD's having well-defined excited-states have been grown in the active region of devices and results will be presented for lasers, detectors, or for structures displaying optical memory effects. For example, QD laser diodes with well-defined electronic shells are fabricated, and shape-engineered stacks of self-aligned QD's are used to increase the gain in the active region. Lasing is observed in the upper QD shells for small gain media, and progresses towards the QD ground states for longer cavity lengths. We obtained at 77K thresholds for J_th=15 A/cm² for a 2 mm cavity lasing in the first excited state (p-shell), and at 300K for a 5 mm cavity, J_th is ~430A/cm² with lasing in the d-shell. For an increased QD density, J_th is smaller than 100A/cm² at room temperature. For inter- sublevel transitions, we demonstrated broadband normal incidence detection with responsivity approaching 1A/W at a detection wavelength of 5 microns. For interband detection, the photoluminescence decay time of p-i-n diode can be changed from ~3nsec to ~0.3nsec (3Ghz) with a reverse bias. For Qds capped with less than ~10 nm, remarkable charge transfers between QD and surface states lead to optical memory effects lasting over time-scales of several minutes.

Self-assembled quantum dot has been realized in different optical-electric material systems and different growth techniques using Stranski-Krastanow growth mode [1]. The optical properties of quantum dots are of physical interest due to the experimental investigation. The theoretical predictions of quantum dot device have been well verified [2]. In the article, we studied the temperature dependent electrical and optical properties [2,3] of quantum dot under normal incidence. From the measurement results, we found the three-dimensional confinement of QD structure and the inter- confined state [4-6].

The Stranski-Krastanov (S-K) self-assembly process produces quantum dots with a large distribution of sizes. In the S-K growth mode, the in-plane spatial distribution of dots is quasi-random. Different strategies have been used to narrow the size distribution and increase the dot-dot spatial correlation. Here, we report a simple method to reduce the height of taller dots by using the P/As exchange exhibited during CBE growth. The fabrication of InAs/InP quantum dots self-assembled into linear arrays through growth on patterned substrates is described. Photoluminescence from one-dimensional arrays is compared with the non-correlated case of quantum dots grown on planar substrates. The interplay between size and spatial distributions is discussed.

In this work, we conduct a theoretical analysis of the design, fabrication, and performance measurement of high power and high brightness strained quantum well lasers emitting at 0.98 (mu) m. The material system of interest consists of an Al-free InGaAs/InGaAsP active region and AlGaAs cladding layers. The laser material is grown by metal-organic chemical vapor deposition and demonstrates high quality with low threshold current density, high internal quantum efficiency, and extremely low internal loss. High performance broad-area multi-mode and ridge- waveguide single mode laser devices are fabricated. For 100 (mu) m-wide stripe lasers having a cavity length of 800 (mu) m, a high slope efficiency of 1.08 W/A, a low vertical beam divergence of 340, a high output power of over 4.45 W, and a very high characteristic temperature coefficient of 250 K were achieved. Lifetime tests performed at 1.2-1.3 W (12-13 mW/(mu) m) demonstrates reliable performance. For 4 (mu) m-wide ridge waveguide single mode laser devices, a maximum output power of 394 mW and fundamental mode power up to 200 mW with slope efficiency of 0.91 mW/(mu) m are obtained.

(110)-oriented GaInAs(P) quantum well lasers along [001] direction have been fabricated to investigate growth direction effects of the QW structure on laser performance. The structures were grown by two methods; MOVPE and MOMBE. Threshold current densities of the QW lasers were investigated for wide stripes aligned in the [001] and [110] directions from the same wafer. As there is no cleaved facets for lasers along [001] direction, the mirror facets were formed parallel to the (001) face by reactive-ion- etching (RIE) using Bbr³ gas. Strong in-lane anisotropic lasing characteristics in the lasers made of the (110)- oriented QW structures were observed between the [001] and [110]cavity directions. This strong anisotrophy in J_th is believed to come from the stronger oscillator strength in the [001] direction. Fairly low threshold current densities of less than 0.6 KA/cm² were obtained for the lasers with cavities along [001] direction in spite of the lower reflectivity of the RIE-etched mirror surface. The result in this research shows the expected advantage of the (110) lasers along the [001] cavity direction and suggests an advantage of the (110) QW structure in the application for long wavelength surface emitting lasers.

New methods of implementing quantum well intermixing (QWI) in InP-based materials using defect-enhanced diffusion are presented and compared to the widely reported technique employing dielectric (usuall SiO₂) capping with subsequent rapid thermal anneal (RTA) treatments. The new methods discussed use InP layers grown either at low temperature by gas-source molecular beam epitaxy (GSMBE) or using He-plasma-assisted GSMBE where growth surface is subjected to a continuous low energy He-plasma generated in an electron cyclotron resonance (ECR) source. The two new QWI processes, and the SiO₂ capping method, are applied to a 1.55(mu) m InGaAsP multiple quantum well laser structure. For application of the QWI process the laser structure growths are interrupted in a manner and location appropriate to carrying out the QWI process and subsequent grating etch for the fabrication of a distributed feedback (DFB) laser. After implementing the QWI and grating etch, growth on the top cladding and contact layers completes the device structure. Finally, the fabrication of a DFB laser with an integrated electro-absorption (EA) modulator is described and the resultant characteristics given.

Resonant-cavity light-emitting diodes (RCLEDs) are attractive light sources because of their applications in data communications, optical printing, display, and optical interconnects. Lower intensity LEDs with a modulation bandwidth of few hundred MHz are suitable for lower-speed optical fiber communications. In this work, we have made oxide-confied AlGaAs/GaAs RCLEDs for optical communication systems. The epitaxial layers of the RCLEDs were grown by MBE system on the N⁺-GaAs substrates. T he RCLED epitaxial layers mainly consisted of an n-type DBR (diffractive Bragg reflector), a p-type DBR, and an active region sandwiched between p- and n-type DBR's. The thickness of the optcal cabity is 1$lamda. Reflectance measurement of the RCLED expitaxial wafers showed that the resonance of the RCLED cavity were about 850 nm. The wet oxidation process, which defined the current conducting aperture, was done at 425 degree(s)C under nitrogen flow with steam. P-ohmic and n-ohmic contacts were then formed sequentially using electron beam evaporation and annealing. The optical power of the RCLED is measured as function of current and temperature. The beam pattern and the optical spectrum were also measured and analyzed.

A new mechanism of tunneling-regenerated multi-active region LEDs with high quantum efficiency and high brightness has been presented. The layer structure, MOCVD growth, device technology, a several of measured curves and their analysis of these new mechanism LEDs were shown in the paper. It was theoretically and experimentally resulted in that efficiency of the electro-luminescence and the on-axis luminous intensity can linearly increase approximately with the number of active regions.

A comprehensive analysis of the phase InGaAsP quaternary lattice-matched to the (100) oriented InP substrate was carried out. Here we used a very efficient computation method, the Levenberg-Marquardt least squares minimization method, to look into the Ga$1-x)As_yP$1-y) phase diagram in great detail. We obtained a novel result: Two solutions are available for each solid ingredient in InGaAsP. One of the solutions is new, while the other agrees well with the empirical expressions relating the solution and solid compositions in the temperature range of 570 degree(s)C ~660 degree(s)C for the growth of In_xGa$1-x)As_yP$1-y) on (100) InP substrate.

Liquid phase epitaxy (LPE) is an important technique to grow GaSb-based materials of good crystal quality. Normally, one has to lower the growth temperature below the liquid-phase liquidus temperature to realize supercooling of the liquid phase. Here we bring forth a new type of LPE, pressure- variation LPE (PV-LPE), where a varying pressure is used to realize supercooling of the liquid phase even though the growth temperature is kept constant. Calculations show that there exists a simple relationship between the liquid content and pressure, which theoretically illustrates that crystal growth could be easily controlled by changing the pressure.

Room Temperature (RT) Infrared (IR) Reflectance spectra are studied both theoretically and experimentally on 3C-SiC films grown on silicon (100) substrate by low pressure chemical vapor deposition (LPCVD). By the use of transfer matrix method, the spectral features influenced by film thickness, phonon-damping constant and free carrier concentration are systematically studied. Comparisons of reflectance spectra are made between experimental spectra and those of ideal samples. A modified effective medium model with consideration of the presence of interfacial layer is introduced to interpret some unusual features. Although some of our results are qualitative, careful analysis of reflectance spectra does provide valuable information about film quality.

Molecular beam expitaxial (MBE) grown GaAs at low substrate temperature (LT-GaAs) possesses a unique combination of properties (i.e., semi-insulation and short carrier lifetime) that has led to a variety of electronic and photonic device applications. In this paper, we report on the optical characterization of LT-GaAs, including carrier lifetime, photoreflectance (PR), and surface photovoltage (SPV) measurements. The undoped LT-GaAs samples were grown using our ow custom designed MBE system at the following substrate temperatures: 200 degree(s)C, 250 degree(s)C and 300 degree(s)C. These sample were then annealed at 7000-850 degree(s)C in a rapid thermal annealing (RTA) system. The PR spectra revealed that the PR amplitude depends strongly on the carrier lifetime, while the PR spectral broadening of near bandgap peak depends strongly on the internal field non-uniformly caused by buried Schottky barriers around the As precipitates. Above bandgap SPV measurements revealed a unique SPV spectrum compared with that for bulk GaAs. Carrier lifetime was measured for LT-GaAs samples grown at 200, 250, and 300 degree(s)C, respectively, and annealed at 700 degree(s)C for 30 seconds, and the corresponding carrier lifetimes at 1.5, 2.2, and 12 ps.

A robust impurity free quantum well intermixing process has been developed that allows complex photonic integrated circuits to be fabricated. Characteristics of the process are discussed and its attributes summarised. The use of the process in three widely differing fabricating applications is described: high-power high-brightness AlGaInP semiconductor laser diodes, nonlinear GaAs/AlGaAs waveguide devices and InGaAsP/InP crosspoint switches.

With the advent of erbium - doped fiber amplifers (EDFA), the fiber loss in the 1550 nm window can be easily compensated and the transmission distance extended even to few thousands of kms without the use of electronic regenerators. However, inorder to utilize the vast transmission capacity of the Single mode fiber, the positive chromatic dispersion exhibited by the existing standard single mode fibers remains to be the primary limitation. This development has motivated the researchers to find new techniques for compensating the positive dispersion of the existing single mode fiber network. It has been demonstrated that higher order modes exhibit large negative dispersion when operated closet o their cutoff wavelength. This negative dispersion can be used to compensate the positive chromatic dispersion of the existing single mode fiber. In this paper we discuss the issues related to the design and optimization of a passive device, dispersion compensating fiber (DCF), which is capable of compensating the chromatic dispersion of the existing fiber over a wide wavelength span from 1500 nm to 1600 nm. This wavelength range encompasses both the bandwidth of EDFA and the low attentuation window of single mode optical fiber. A finite element method (FEM) is used to calculate the dispersion characteristics of a single mode optical fiber with arbitrary refractive index profile. Computer simulations shows that an optimally designed dispersion compensating fiber can reduce the dispersion of standard fiber from 18.62 ps / km - nm to 0.45 ps / km - nm over the entire wavelength span, when it is added with the existing standard fiber in a ration of 20.56:1.

Recent advances in the preparation of B i- and Ce- substituted (doped) yttrium iron garnet (YIG) films on gadolinium gallium garnet (GGG) and semiconductor substrates such as gallium arsenide (GaAs), the design of hybrid material structures, and the construction of wideband integrated microwave and magnetooptic (MO) devices, and their potential applications are presented.

With using 5 glass spheres of 5mm diameter, a linear and a curvilinear array arrangement were realized and an image on a paper was transferred similarly for both arrangements. When the number of sphere was varied in the array, the transfered image was varied form normal to reversed and reversed to normal. By using polystyrene micro-sphere of 10 (mu) m diameter, a laser light was propagated in a linear and a curvilinear array. For a laser light at a wave length of 670nm, the attenuation coefficient was evaluated to be 0.051dB/sphere in the linear array. The attenuation coefficient was increased for the curvilinear array. The image and the light transfer in the sphere array are attractive for new optical device application.

We report an experimental study of the preferential input and output side coupling of oval-shaped optical microcavities. The cavity was in the cross-section of an oval-shaped dye-doped glass fiber, which was optically pumped perpendicular to the fiber axis. Fluorescent emission perpendicular to the fiber axis was imaged with a lens onto a CCD camera. The integrated intensity of the image profile at different angles provided the far-field angular pattern of the fluorescent emission peaked at ~ 45 degree(s) relative to the cavity major axis. The near-field spatial profiles revealed refractive output coupling from an extended high- curvature region. A simple ray-path model was used to calculate the fluorescent near-field spatial profile. Preferential input side coupling was also observed in the direction ~45 degree(s) relative to the cavity major axis. By focusing the pump beam at the high-curvature region in the preferred coupling direction, we observed ~ a factor of 8 enhancement in the integrated intensity at the preferred fluorescence output angle. By imaging the fiber top surface, we demonstrated that the preferentially input coupled light could be guided along the cavity circumference.

A novel three-branch optical power divider by Ti diffusion on lithium niobate is proposed and analyzed. For the conventional three-branch power divider, most of the optical power is transmitted to the central output waveguide and only little power is distributed to the two sideward output ones. Several designs have been proposed to increase the power in the two sideward output waveguides. Because they require extra regions of indices lower than that of substrate or higher than that of waveguide, it is difficult to find such indices for realizing their designs. In this work, we propose a novel three-branch optical power divider, which includes one substrate and waveguide, the realization of the proposed devices becomes very easy. Prior to the diffusion process, only one lithography step is required. For the proposed structure, the transmitted power in the two sideward output waveguides can be higher or lower than that in the central output one under a large branching angle. It is known that the index distribution in the Ti-diffused waveguide is varied with the diffusion process parameters. In order to understand the effect of waveguide fabrication parameters on power distribution in three output waveguides, the parameter variations are considered. Moreover, in comparison to the previous works, the proposed power divider has the advantages of low insertion loss, large branching angle, and easy fabrication.

Temperature- and field-dependent electroluminescence and quantum efficiency have been investigated in tris-(8hydroxy) quinoline aluminum (Alq₃)light emitting diode over the temperature range from 10K to 300K. It has been observed that up to a certain temperature luminescence intensity decreases with decreasing temperature and then saturated in the low temperature region. The quantum efficiency increases with decreasing temperature and finally reaches to almost a constant value. At lower applied voltage, two peaks have been observed in the quantum efficiency with temperature. The two peaks are attributed due to deep trap levels (high temperature regime) and shallow trap levels (low temperature regime) in Alq₃.

We have studied the electronic structure, absorption, and photoluminescence of poly(1-phenyl-2-alkynes) - [C₆H₅)C- C(C_mH_2m+1)]_n-(m = 1, 2), poly(phenylacetylene)-[HC=C(C₆H₅]_n- and its derivatives -[HC=C(C₆H₄-p-R]_n with various non- liquid crystal ring substitutes. For poly(1-phenyl-2- alkynes), the PL efficiency is very sensitive to the molecular structure of the alkyl pendant and can be enhanced up to 50 times as the alkyl side-chain increases in length. But for poly(phenylacetylenes), their luminescent efficiency can be improved several times only as the tail becomes bulky. Regardless of the types of the pendants, the emission color of the polymers is pineed at ~450 nm (2.7eV). The band structure of the polymers, which has been calculated using extended Huckel tight-binding method, is essentially an ensemble of the backbone (extended states) and the pendants (localized states), and the processes of optical absorption and blue emission are confined in the directly attached aromatic ring. The interaction between the pheny chromophore and its nearest neighbors is of vital importance in improving the emission efficiency. Although the band gap of the backbone can be enlarged by the pendant, its (pi) - (pi) ^* interband transistion is insignificant for the blue emission.

A new four vacuum chamber evaporator for organic devices was proposed and specially designed. The chamber one is for ITO/glass pretreatment, it's have ozone treatment and plasma treatment. The chamber two is used for organic thin film evaporating. There has six sources for organic material, and three power sources can work at the same time, there is a mask storage chamber in the organic evaporation chamber, so for some material research, you can get three kind of doping density of thickness OLED at the same fabrication. The chamber three is a vacuum glove box. It's used for package. The chamber four is used for cathode evaporating, it can evaporates Mg, Ag, LfF, Ca, Al, Au.

A novel blue organic light emitting diode is fabricated based on a new organic material. Dipyrrole3, which can emit a pure blue light. The Dipyrrole3 is used as a dopant and is doped into an electron-transporting hose. NPB is used as the hole transport layer. The device consists structure or ITO/NPB/Begg2:Dipyrrole3 (100:5)/BePP2/LiF/Al. It shows a bright blue light emission layer at 451nm and 480nm, the full width at half maximum is 61nm. The maximum luminescence is 2600cd/m² at a voltage of 20V. The peak power efficiency is 0.7651m/W at a voltage of 7V.

This paper describes the spatially and temporally resolved images from submicron NFETS and a CMOS ring-oscillator circuit. The spatial and temporal information is supplemented by spectral measurements obtained using a set of optical band-pass filters. The intensity of luminescence has been observed on individual transistors with gate-length downs to 0.2 microns. The time-resolution of ~ 100 ps is sufficient to observe the response of individual invertors for gate lengths of 0.8 microns and even lower. Preliminary work on spectral distributions on emission from both the ring oscillator and NFET indicated a peak around 850nm. This may be limited on the long-wavelength side by the response of the photomultiplier photocathode, indicating that better sensitivity could be achieved with extended infra-red sensitivity. The spectral distribution is explained with reference to current theories.

A technique, based on quantum well (QW) intermixing, has been developed for the post growth, spatially selective tuning of the QW bandgap in a semiconductor laser structure. High energy (MeV) ion implementation is used to create a large number of vacancies and interstitials in the device. During high temperature processing (rapid thermal annealing), these defects simultaneously enhance the intermixing of the QW and the barrier materials, producing a blue shift of the quantum well bandgap, and are annealed out. Increases in the bandgap energy of greater than 100 nm at 1.55 (mu) m in InGaAs/InGaAsP/InP structures can be achieved, while absorption losses are unaffected or reduced. Absorption spectroscopy in the waveguide geometry is used to quantify any excess loss in the structure. Using a simple masking scheme to spatially modify the defect concentration, different regions of a wafer can be blue shifted by different amounts. This allows the integration of many different devices such as lasers, detectors, modulators, amplifiers and waveguides on a single wafer using only a single, post-growth processing step. The performance of both passive (waveguide) and active (laser and amplifier) devices produced using this technique will be described, as well as the practicality of this technique in the production of photonic integrated circuits.

Wavelength demultiplexing photodetectors was fabricated using selective intermixing of InGaAs/InGaAsP multi-quantum well (MQW) structure. As InGaAs/InGaAsP MQW with U-InP cladding layer and U-InGaAs cap layer grown by metal organic chemical vapor deposition (MOCVD) was used for this experiment. Intermixing of InGaAs/InGaAsP MQW structure was done by a rapid thermal annealing after depositing SiO₂ dielectric layer on the InGaAs cap layer by plasma-enhanced chemical vapor deposition (PECVD). Three sections of shorter-wavelength PD, absorber region and longer-wavelength PD lined up linearly and the front two regions were intermixed. Output current ratios of fabricated photodetectors at wavelengths of 1550 and 1480 nm were about 20dB and thus the photodetectors were proven to demultiplex both wavelengths.

The concentration effect of the spectroscopic properties Yb³⁺-doped borate glasses have been determined from absorption and emission measurements at room temperature. The systematic variations of the spectroscopic properties and laser performance parameters with activator concentration can be used to optimize the doping concentration.

In this paper, we have applied a perturbative expanding method to the hopping model, and studied the coupling effects of modulation depth between two pieces of photorefractive phase gratings stored in one point with an external applied dc field. The coupling equations of modulation depth and their steady solution have be derived. It has been found that the spatial -charge-filed of one of the two gratings is seriously affected by the modulation depth of other gratings.

In this paper, a simple wavelength conversion scheme based on SLAOLM is proposed out for the first time, and its extinction ratio performance and noise characteristics can be improved simultaneously. Theoretical study shows that the conversion mechanism is still based on gain saturation effect, but the phase modulation effect existing in SLAOLM is helpful for extinction ratio improvement. Furthermore, the weak signal will be compressed and the strong signal will be amplified in the SLAOLM, then the Signal-Noise Ration (SNR) can be also improved. Experiment results shows that, after exploiting this scheme, the output extinction ration has been improved to be 10dB from 6dB, and the SNR has also been improved to be 13dB from 5dB.

A SPICE circuit model for semiconductor lasers is developed to simultaneously incorporate the effects of the carrier and lattice heating. Numerical simulations for the dc, ac and transient responses of this circuit model are demonstrated. The circuit model is transformed from the rate equations that govern the dynamics of carrier density, photon density, electron temperature, hole temperature and lattice temperature in the active region of semiconductor lasers. SPICE codes are developed exactly according to this circuit model. This results from this work demonstrate the capabilities and versatilities of the SPICE circuits in simulating the complicated carrier and lattice heating processes for semiconductor lasers. The possibility of simulating optoelectronic systems in conjunction with electronic circuits and devices all by SPICE circuit models is also discussed.

A DVD disc signal measurement device is introduced in this paper. The device is fed high frequency signal and EFM+ signal from a DVD disc driver. By using EFM+ signal as input reference, the device is capable of recording all the peak (or bottom) values of a specified xT signal in an user defined duration. To improve the accuracy of the measurement device, the ac and dc components of high frequency signal are proceeded individually and then combined to give the corrected peak (or bottom) values. The corrected peak value is given by adding the dc component and the peak fo the ac component. The corrected bottom value is given by subtracting the peak of inverse AC component from the dc component.

Silicon will play a practical role in the future of optoelectronic devices. Silicon microelectronics fabrication techniques can be largely exploited to fabricate low-loss and high volume optical devices. In this paper, we report the concept and realization of new two-dimensional 1x16 and 1x32 array waveguide optical power splitters that offer the possibility of a free choice of the output power ration in silicon-on-insulator (SOI). The power splitters compose one dimensional multimode interference (MMI) optical power splitter and multi-layers coupler at wavelength at 155 (mu) m. According to the design, we can reduce the size of SOI power splitters waveguide without increasing propagation loss, efficiently. The results achieved show a remarkable improvement with respect to those of classical MMI power splitters.

Real-time effect was investigated with the binary masks and contact copy method in the processing of sol-gel hybrid material. The height of the real time relief increases slowly with the increase of exposure dose, but is no relation with the variation of the spatial frequency of the mask. Moreover, the height of the real-time relief is dependent on the thickness of the film deposited on the substrate. Compared with the mask, the spacing of the exposed areas in sol-gel film shrinks, and the shrinkage rate is about 10-20%. The possible reason causing the real- time effect is discussed.

An optical waveguides spectral filter constructed with a W- index waveguide, supporting a dominant mode with nonzero cutoff frequency, and a Step-index waveguide is proposed an analyzed. The proposed filter offers a spectral width on the order of one nanometer, considerably narrower than that provided by a filter made of two Step-index waveguides having the same transmission wavelength. T he narrow spectral width is achieved by exploiting a relatively large slope difference between the dispersion characteristics of the W-index and Step-index waveguides constituting a filter. For an example case, transmission characteristic of the proposed filter with peak transmission at 1.55 (mu) m is calculated and compared with that of a corresponding filter made of two Step-index waveguides.

In this paper, a new 1x4 multimode interference (MMI) SOI optical interconnects based on waveguide technology is presented. The MMI couplers including 2-D periodic air pads are analyzed. Especially the output powers adjustment of MMI SOI optical interconnects with considering the positions of those 2-D periodic air pads is studied. The SOI waveguide MMI interconnects is designed at wavelength 1.55 (mu) m region. We use beam propagation method to analyze the mode pattern. The mode patterns give the information of the power distributions of the output plane induced by guided wave propagating through those air pads. We analyze two cases or layout 40 pads and 70 pads for comparison.

In this paper, we design two tapered waveguides on the silicon-0n-insulator (SOI) wafers. The shape of designed SOI waveguides are linearly and exponentially taping varied along the propagation direction. The width of our designed SOI waveguide at starting point is 6 (mu) m, the end width is 20 (mu) m. We find out the optimal light launching position for maximum power output with single mode pattern. The linearly and exponentially tapered waveguides are compared. Finaly, we add a polymer layer as a cladding layer, the difference between the exponentially tapered waveguide and the linearly tapered waveguide with the polymer cladding are analyzed. The best deign of the tapered SOI waveguide with polymer cladding is obtained.

In this paper, we analyze the polarization variation of semiconductor optical amplifier (SOA) induced by temperature variation. This work is motivated by the requirement of high-speed optical signal transmission in fiber communication networks with using SQAs. Experimental polarization Stokes parameters are measured. The degree of polarization shows monotonically decreasing with temperature increasing. The temperature variation of SOA is monitored between 14 degree(s)C to 33 degree(s)C. Our work is helpful for measuring the temperature effect on polarization of SOAs for application in optical communication systems.

Photoreflectance (PR) measurements on an n-GaAs epitaxial layer as a function of the intensity of pumping light are reported. Based on the thermionic emission theory and current-transport theory, the pinning position of surface Fermi level can be determined from the dependence of the PR signal on the pumping light intensity. Experiments demonstrated that the PR amplitude depends upon the optical excitation intensity I as ln((gamma) I), which is normally the case experimentally and theoretically. From the analysis of the dependence on the amplitude of PR on optical excitation intensity, the surface Fermi level of GaAs at room temperature about 0.72 +/- 0.02 eV below conduction band was evaluated easily and directly. This result is consistent with those accurately reported results using PR to characterize samples with specially designed complex surface-intrinsic-doped structures for obtaining a uniform Franz-Keldysh oscillations and derived the built-in electric fields then evaluated the Fermi level pinning position indirectly.

In this paper, a novel polarization analyzer for measuring the state of polarization of light is proposed. The analyzer consists of a TE-TM mode splitter, a passive TE-TM mode converter, and three polarizers. Comparing with the previously reported methods, without using mechanically movable and actively modulated components for polarization control, the time response of measurement is less limited and the signal process for the determination of polarization parameters is easier. Where, the polarization parameters are obtained via three received optical signals based on the proposed methods. Moreover, the concept can be realized by waveguide or fiber devices, which are more compact. The dependence of measurement performance on the characteristics of composed elements is theoretically investigated and the results show that the measurement resolutions are determined mainly by the characterisation of individual elements.

A study of find adjustment of the coupling coefficient of Zn-diffused directional couplers on Z-cut lithium niobate substrate by a series of post thermal-treatment is presented for the first time. Optical mode profiles and propagation losses before and after the treatments are measured for the 1.32 (mu) m wavelength. Experimental results show that the post thermal-treatment is quite efficient for fine adjustment of the cross coupling power ration of the directional coupler.

Most microelectronic devices and sensors are fabricated by using thin film deposition. Understanding metal oxide films is important in the electronic applications. We report an improved interferometric method based on a phase shifting technique to determine the mechanical properties of metal oxide films. Thin films were prepared by ion-beam sputter deposition at low substrate temperature. Quantitative determination of the mechanical properties such as the internal stress, the biaxial elastic modulus and the thermal expansion coefficient were investigated. A phase shifting Twyman-Green interferometer wiht the phase reduction algorithm was set up to measure the stress in thin films. Two types of circular glass plates, with known Young's moduli. Poisson's ratios and thermal expansion coefficients, were used as coating substrates. The temperature-dependent stress behavior of the metal oxide films was obtained by heating samples in the range from room temperature to 70 degree C. The stresses of thin films deposited on two different substrates were plotted against the stress management temperature, showing a linear dependence. From the slopes of the two lines in the stress versus temperature plot, the intrinsic stress, the biaxial elastic modulus and the thermal expansion coefficient of metal oxide films are then determined.

Miniature micromachined Fabry-Perot interferometers (FPI) are composed of the corrugated silicon diaphragm and glass substrate. The flatness of the silicon diaphragms with a dimension of 4.2 mm in diameter can be controlled within 0.12 (mu) m. The optical depostion condition to grow thin Au films, as a reflector of FPI, can be established by studying the optical properties Au-photoresistent-As etalons. The interference spectra of micro-machined gap-tunable FPI with a structure of Si-Cr-Au-air-Au-Cr-glass have been observed in the near infrared regions. The transmittance and FWHM bandwidth of the as-bonded FPI is 5.6% and 3.84 nm at a peak wavelength of 1578.4 nm, respectively.

A 256x256 backside illuminated photovoltaic indium antimonide (InSb) focal plane arrays having spectral response in the medium wavelength infrared (3 to 5 (mu) m) was designed and developed at Chung Shang Institute of Science and Technology for use in a variety of military and commercial applications. Operating at 77 degree(s)K, the arrays had a mean laboratory detectivity of 3.12x10¹¹cmHz^½/W with f/3 optics. The responsitivity non-uniformity was 3%, and the operable yield exceeded 99%. The FPA achieves an Noise Equivalent Temperature Difference (NETD) is less than 0.025 degree(s)K at 300 degree(s)K background with f/3 optics.

Cosputtering of titanium oxide films with aluminum (al), fuse silicon (SiO₂) and silicon (Si) is investigated. Their optical properties, surface morphology and structure show better than pure titanium oxide. In general, the extinction coefficient and surface roughness of the cosputtered films are smaller than the pure TiO₂ film. Also, the microstructure of the cosputtered films are improved to an amorphous structure even though post-baked up to 450 degree(s)C.

Using two optical techniques, we have measured the Frohlich interactions between electrons and optical phonons on a number of different Be-doped GaAs/Al_xGa_1-xAs multiple quantum well structures. Raman scattering measurements at 15 K are presented for GaAs/Al_xGa_{1- x}As quantum wells with Al compositions of x=0.3,0.5,0.7 and 1.0. And also for GaAs/AiAs, GaAs/Al_0.7Ga_0.3As with fixed well width of 50A and barrier with between 5 to 120 A. The GaAs-like and AlAs-like phonon frequencies of the first-order modes are measured as a function of Al composition and barrier widths. We have also performed hot electron - neutral acceptor luminescence in order to determine average optical phonon energies emitted by the photoexcited electrons in quantum wells with the acceptor levels of the GaAs wells. It is shown that the relaxation of hot electrons in the GaAs/Al_xGa_1-xAs quantum wells is dominated byt the GaAs LO phonon emission for small x, but by AlAs-like LO phonons for larger Al compositions. For the quantum wells with largest barrier width of 5 A, the energy of emitted LO phonon decreases to a value close to the GaAs Lo phonons, nevertheless, there is still a significant contribution from the emission of AlAs-like modes.

Indium nitride (InN) film was successfully grown on the Si(111)substrate. The growth rate of InN film can be enhanced about four times by a novel-designed MOCVD system with a NH₃ pre-cracking device, in which the NH₃ was fed through a quartz tube passing over a high temperature (650-850 degree(s)C) graphite. A maximum growth rate of about 6 (mu) m/hr in our system was achieved due to high cracking efficiency of NH₃. The growth temperature of substrate widely ranged from 350to 600 degree(s)C provides more flexible conditions to improve the film quality. The X-ray diffraction peaks of 31.7 degree(s) and 65.5 degree(s) were obtained from the (0002) and (0004) InN respectively, indicating (0001)-oriented hexagonal InN was epitaxially grown on the silicon(111) substrate.

AlGaInP light emitting diode (LED) with a mirror substrate has been successfully fabricated by wafer bonding. The bonding technique using a metallic interlayer has been developed to eliminate handling the fragile, free-standing epilayers. Various structures of the mirror substrate have been studied, and a suitable structure of Au/AuBe/SiO₂/Si is proposed. From the observation of the chip fabrication process, it was found that the SiO₂ layer could isolate the stress causing from the Si substrate. The device performance of bonded LED is obviously far superior to that of the standard absorb-substrate LED. It exhibits normal p-n diode behavior with a low series resistance. Moreover, the emission wavelength of the bonded LED was independent of the injection current. The low forward series resistance and a good heat sink provided by Si substrate solve the joule heating inhering in conventional LED problem. Furthermore, the bonded LED with high reliability has been demonstrated.

The photoreflectance has been measured on InGaAs/GaAs multiple strained quantum wells structures at room temperature. The Franz-Keldysh Oscillation (FKOs) features are clearly observed on photoreflectance spectra. Based on FKOs features above the energy band gap, the built-in electric field was studied by conventional FKOs calculation and the Fast Fourier Transform, and Airy function fit techniques. The built-in electric fields were evaluated and discussed. The results show that Fast Fourier Transform could provide an accurate and fast method to calculate the built-in electric field.

The long-term transient spectra of heavily Mg-doped GaN have been investigated. As the excitation power density increased, the broad Mg-induced emission band showed blue- shift revealing characteristic of donor-acceptable pair (DAP) recombination. We also observed an unusually slow intensity decay. The characteristic time constants range from several tenths to a few hundred seconds for emission between 360 and 460 nm. Our results are interpreted in terms of metastability due to compound effects of differential DAP population and recombination rates and uneven acceptor distribution.

ZnSe is an important semiconductor material with a large bandgap (2.68 eV), which has the potential to be used for photoluminescent and eletroluminescent devices and for window layer of solar cells. In this work, a low-cost and large-area growth method for ZnSe layer on Si substrate was studied by liquid phase deposition (LPD). The micrograph of the surface shows specula but a roughness surface texture is obtained. The island texture could be improved by raising growth temperatures. The crystallinity could be improved by the growth temperature considerations. High resistivity and specular layers were obtained as grown at room temperature. The abrupt interface resulted from less interdiffusion between ZnSe layers and substrates was reasonable under the growth condition at room temperatures.

Ga K-edge extended X-ray absorption fine structure (EXAFS) measurement was employed to investigate the local structure and GaN:Mg films grown my metalorganic vapor phase epitaxy (MOVPE) with various Cp₂Mg dopant flow rates using both in-plane and out-of-plane polarization modes of X-rayu. The near edge absorption spectra were found to depend on X-ray polarization strongly for undoped GaN sample and weakly to minutely for heavily Mg-doped and amorphous films. The results indicate Mg incorporation modifies the local structure around the absorber Ga atom and, hence, alters the molecular orbital electron transition of GaN sample. EXAFS analysis shows both vacancy an dMg-interstitial defects contribute to the reduction of coordination numbers along the hexagonal c-axis of GaN:Mg film.

In this paper, a novel, fast, and accurate method to predict the energy bandgap E_g in Ga_xIn_1-xAs_yP_1-y quaternary compounds by using fuzzy theory and neural network is proposed. It has been developed to analyze the energy bandgap due to the adjustable ratios x and y of quaternary compounds. The prediction results are compared with experimental data obtained from actual devices. A good agreement (error < 0.75%) has been obtained on the energy bandgap versus the adjustable ratios x and y of quaternary compounds.

GaAs-based high-speed photodetectors attract lots of attention in the past twenty years due to their maturity in material growth and processing. However their wide bandgap characteristic (830nm) restricts their applications in fiber communication wavelength (1.3(mu) m~1.55(mu) m). Recently some research groups had demonstrated GaAs-based n-i-n, p-i-in waveguide type photodetectors operating at 1.55 (mu) m by taking advantage of the mid-gap defect absorption of low- temperature grown GaAs (LTF-GaAs). In this paper we propose and analyze different bandwidth-limited factors for LTG-GAAs based metal-semiconductor-metal traveling wave photodetector (MSM TWPD) for both long and short wavelength cases. According to our calculation results, MSM TWPDs release the bandwidth limitation bottleneck in previous n-i-n and p-i-n TWPD structures, especially in the long wavelength case. Our analysis indicates that Lt-GaAs based traveling-wave photodetectors can offer excellent bandwidth as well as high saturation power performances in fiber communication wavelength, which corresponds to long absorption length regime.

A novel electrically tunable fiber Bragg grating (FBG) laser is reported. The FBG can be coupled to the fiber efficiently. The FBG is pasted on the surface os a magnetostrictive rod. The magnetostrictive rod is placed in a solenoid and it stretches under a magnetic field. Then the FBG is tuned, and the laser's wavelength alters. The tuning range is 1.6nm, the line-width is narrower than 0.3nm.

In this article, we report the effects of RTA on Mg-diffused GaN thin films and Al/Mg-diffused GaN Schottky diodes. After Mg-diffusion process, the samples were exposed to RTA treatment the temperature from 800 to 900 degree(s)C. The samples were studied by variable temperature Hall effect measurements, and PL spectroscopy. The reduced resistivity by higher RTA temperature is due to the increased activated acceptor. Evidence, showed that both near-band-edge emission and deep level luminescent in PL spectrum could be all enhanced by raising the RTA temperature. Considering the Al/Mg-diffused Schottky diodes, the higher RTA temperature resulting in the superior forward conduction characteristics are suggested to be due to the more concentrations of hole and lower resisivity of GaN thin film. However, the greater reverse leakage current and lower breakdown voltage were deduced to be the creation formation of Ga-Al compounds at the metal-semiconductor interface.

In our previous work, we first propose the Au/AuBe is a good ohmic contact material to p-type ZnTe. After apply the material to II-VI light emitting diode, the operation voltage as low as 2.4V can be observed. The II-VI blue light emitting diode (LED) were grown in a RIBER 32P system with Zn(6N), Se(6N), Te(6N), Cd(6N) on (001) GaAs+ substrate. The structure consisted of a GaAs:Si(n+) buffer layer, ZnSe:C1 (0.5um), ZnSe(200A)/ZnCdSe (100A) multiple quantum well, ZnSe(200A), ZnSe:N(0.3um), ZnSe:N/ZnTe:N multilayer and ZnTe:N (300A). Standard photolithography technology was doen to fabricate the diode. The mesa etch was done by (formula available in paper) etching solution. The p-type ohmic was done by AuBe/Au metal. The emission wavelength was 530nm (room temperature) and 495 (30K) with 2.4V under CW operation. Since low operation voltage introduced less heat in the device, better thermal behavior can be expected with this low operation voltage.

The InGaN semiconductor materials have important applications in short-wavelength light emitting diodes and semiconductor lasers. In this work, we study the optical properties of a single quantum well and a multiple quantum well InGaN devices experimentally with a photoluminescence measurement system and numerically wiht a commercial Lastip simulation program. Important optical parameters such as the peak wavelength, the emission intensity, and the bandwidth of the photoluminescence spectra at various temperatures and pump power levels are characterized and compared to the results obtained from the Lastip numerical simulation. The effects of the indium concentration in quantum well, the well width, and the bowing parameter on the optical properties of the InGaN quantum well structures are also studied numerically with the Lastip simulation program. Good agreement between the experimental and numerical results is observed.

The Cr:YSO solid-state crystal has broad absorption bands in visible and near infrared spectral region. Although Cr:YSO was originally developed for laser applications, our experiments and numerical simulations show that it can act as an effective saturable absorber Q switch for the ruby laser at 694.3 nm, for the tunable alexandrite laser from 700 to 818 nm, and for the tunable Cr:LiCAF laser from 725 to 840 nm. Since the Cr:YSO is a robust solid-state crystal, the durable Cr:YSO Q-switched solid-state laser systems may find various practical applications. In this paper, theory of passive Q-switching with solid-state saturable absorber is briefly reviewed. Details of the numerical situation for the passively Q-switched solid-state laser systems are presented.

AlGaInP LEDs with emission wavelengths near 570 nm are important in liquid crystal display backlight application. However, high brightness in this spectral region is difficult to achieve due to the reduction of the radiation efficiency in the high-aluminum-containing active region and the smaller band offset between the active and the cladding region. In order to improve the performance of the 570-nm AlGaInP LEDs, we have grown several wafers with different structure designs and studied the optical properties as functions of the device temperature and the excitation power experimentally with a photoluminescence measurement system and numerically with a commercial Latsip simulation program. Specifically, important factors such as the barrier height in quantum wells, the tensile strain barrier cladding next to the MQW region, the compensated strain in MQW, and the disturbed Bragg reflector are investigated. Good agreement between the experimental and numerical results is observed.

We have made AlGaAs/GaAs gain-guided two-dimensional (8x8 and 4x4) vertical-cavity surface-emitting laser array in the 850-nm rage for optical communication applications. Higher optical power with nearly single transverse mode output can be achieved by using high-density two-dimensional VCSEL arrays with smaller emitting element windows (<EQ 5(mu) m). The distributed Bragg reflectors (DBRs) of the VCSELs consist of A1_0.12Ga_0.88As/AlAs quarter-wave stacks. The GRINSCH active region is consisted of an undoped three- quantum well GaAs/Al_0.3Ga_0.7As and two undoped linearly graded Al_xGa_1-xAs confinement layers. The emitting windows of the individual VCSEL elements are 5 (mu) mx4 (mu) m. A high cw optical power of 15.3 mW was measured for a 8x8 array, with a maximum pulsed optical power of 28 mW at 160 mA. The spectrum of the VCSEL array showed single transverse mode characteristics. The near-field characteristics of the arrays were measured. Almost all the VCSEL elements emitted TEM₀₀ mode. The modulation characteristics of the VCSEL arrays were also measured at different operating current.

In this work, we have made AlGaAs/GaAs gain-guided broad- area vertical-cavity surface-emitting lasers (VCSELs) in the 850-nm range. For higher power applications such as optical pumping and optical communications, board-area VCSELs and VCSEL arrays are needed. The distributed Bragg reflectors (DBRs) of the VCSELs consist of Al_0.12Ga_0.88As/AlAs quarter-wave stacks. The GRINSCH active region is consisted of an undoped three-quantum-well GaAs/Al_0.3Ga_0.7As, two undoped Al_0.3Ga_0.7As confinement layers, and two undoped linearly graded Al_xGa_1-xAs layers. The current confinement of the VCSELs was made by proton implantation with an implantation energy of 280 KeV. The emitting window diameters are 30 to 50 (mu) m. A very high cw optical power of 23.4 mW and a pulsed optical power of over 36 mW were measured for a 50-(mu) m aperture device. These VCSELs are suitable for higher power applications. The VCSELs showed multiple transverse mode characteristics. The near-field characteristics and spectrum of the devices were measured and analyzed. The modulation characteristics of the VCSELs were also measured. A 3 dB bandwidth (f_3dB) of 5.6 Ghz was measured for a 30-(mu) m aperture device at 20mA.

This investigation presenst a micromachined optical modulator with electrostatic actuation fabricated by the conventional CMOS process. The modulator is operated by interaction of fixed part, stationary gratings, and movable part, sliding gratings. The period of the gratings varies with the slide of the movable part, thereby allowing different diffraction patterns of the reflected light. In addition, 100% modulation in the first order can serve as an optical switch. All procedures following the CMOS process merely require a simple post-process. With maskless etching, the micromachined optical modulator is developed to obtain a high-aspect-ratio structure and high efficiency of modulation. Compare to the commercially available acoustic ones, the micromachined optical modulator proposed herein is smaller and weigh less.

This investigation presents a novel type of DOEs fabricated by the conventional CMOS process. A simple post-CMOS process is applied to form the relief pattern, which can be used directly for its optical properties or serve as a mold for the subsequent replication. By using the CMOS process, in addition to reducing the depth, alignment, dimension, and shape errors of the pattern, the scale is minimized by the advancing microfabrication as well. The performance of arbitrary DOEs can be directly related to the diffraction efficiency of the gratings. Therefore, in this investigation, the shape of the multi-level gratings is designed and the diffraction efficiency is calculated by the rigorous vector coupled-wave analysis. The largest constraint of the CMOS process for the multilevel gratings is that the depth of each layer is different and unchangeable. However, a suitable length for each level can be determined and, in doing so, the diffraction efficiency can reach 81%.

This investigation presents a concept of integrated device, which tracks the movement of eyeball in real time. Integrated optical components are applied to perform infrared oculography to find the position of the eyeball. First, the photodiodes emits infrared to human eyes via the output coupler, then the reflected light is collected by the input coupler and detected by the photodetectors. By analyzing the electrical signal, we could figure the position of the eyeball out. The basic principle is based on the differential of reflected index between sclera and iris. The light source and detectors are settled on the side of goggles worn and, in doing so, the eyesight could be wide without obstacles. Therefore, the optical guiding interconnection is an essential issue for the eyeball- tracking device. Since the fine line gratings are necessary for the optical coupler, the electron beam writing is used to meet the requirement. The gratings with 40 nm line width are achieved, and it is sufficient for optical coupling. On the other hand, the electrical signal related eyeball position is simulated. We could translate the electrical signal readout into the coordinate of the eyeball position. The whole eyeball-tracking device would be small volume, less weight, and portable.

The effect of PbSn solder joint strength on temperature tests in laser diode packaging has been studied experimentally and numerically. It was found that the solder joint strength increased as temperature cycle number increased. A finite-element method (FEM) analysis is performed on the calculation of joint strength of PbSn solder in temperature cycling tests for laser diode packaging. Numerical calculations were in good agreement with the experimental measurements that the solder joint strength increased as the temperature cycle increased. This is may be due to the redistribution of the residual stresses within the solder during the temperature cycling tests, and hence reducing the residual stresses and increasing the solder joint strength as the temperature cycle number increased. The result suggests that the FEM is an effective method for predicting the solder joint strength in laser diode packages.

The thermally induced fiber alignment shifts of fiber- solder-ferrule (FSF) joints in laser module packaging under temperature cycling tests have been studied numerically by a elastic-plastic finite-element method (FEM). The FSF joints were assembled using both the Pb(37)/Sn(63) and Au(80)/Sn(20) solders. Comparison between the calculated results shows that the Au/Sn solder in the FSF joint exhibits three times less fiber than Pb/Sn solder. This is due to the higher Young's modulus, yield strength, and melting temperature of AuSn hard solder than PbSn soft solder. This suggests that the hard solder of Au/Sn is more suitable for use in FSF assembly than soft solder Pb/Sn for laser module packaging to reduce thermally induced fiber alignment shift. Numerical calculations show that the major cause of fiber shift in FSF joints may come from the plastic solder yielding introduced by the thermal stress variation and the redistribution of the residual stresses during temperature cycling.

Under appropriate conditions, the growth of InGaAs/InP on patterned InP substrates leads to the development of atomically smooth triangular structures with [111]B sidewalls and embedded in InGaAs quantum wells. Using finite element methods, we examine how the stress distribution arising from embedded compressive and tensile quantum well influences the subsequent growth of self-assembled InAs quantum dots on the sidewalls. By calculating the total strain energy of the structure we show that the InAs dots would locate preferentially along the sidewall near the location of a comprehensive quantum well and away from a tensile quantum well. We also show that the size distribution can be narrowed in a three-layer structure that consists of one compressive quantum well sandwiched between two tensile quantum wells.

In this work we present optical investigations of metalorganic chemical vapor deposition (MOCVD) grown InSb thin films on GaAs(100) substrates and MeV ion implanted InSb(111) bulk crystals. Far-infrared (FIR) reflectance spectroscopy has been used to study the lattice vibration behavior of all the samples. For the MOCVD films the effects of III-V source ratios on the films crystalline quality may have been reported. Two additional weak modes in the wavenumber regions of 210-240 cm^-1 are observed and they appeared more prominent at low temperatures. Interference fringe effects modify the FIR reflectance band of the GaAs substrate. They are related to the uniformity of film thickness and crystalline perfection. The relationship between these interference features and film quality as well as thickness uniformity was obtained from the measured spectra. The carrier concentration, mobility, effective mass as well as the dielectric constant of these films have been determined. For the bulk InSb crystals, high energy C⁺ ions have been implanted and MeV energies and, the optical as well as transport properties of the implanted layers have been presented and discussed.

The damage accumulation at the surface as well as deeper regions in InSb bombarded with MeV C⁺ and C₂⁺ ions have been studied. Mirror polished (111)-oriented InSb single crystal substrates were implanted wiht 1.00 MeV C⁺ and 2.00 MeV C₂⁺ ions to a total fluence of 5x10⁴ C-atoms/cm² at room temperature. The retained damage following implantation was analyzed by Rutherford backscattering/channeling technique and Raman scattering experiment. Fourier Transform Infrared Spectroscopy (FTIR) have been used to study the dielectric behavior, optical as well as transport properties of the implanted specimens. The FTIR spectra were analyzed within the framework of a dielectric response model. The surface structure of the implanted wafers has been measured by atomic force microscopy. The results show that the response of InSb crystal to C⁺ ion bombardment is widely different when compared to that of C₂⁺ implantation. A tentative explanation for the results have been presented.

The unadopted polycrystalline diamond films are deposited on p-type silicon substrates by a microwave plasma chemical vapor deposition (MPCVD) system. The deposition conditions are CH_{4?/H(subscript 2}=0.5%, pressure equals 45 torr, power equals 2.2kW, and subtract temperature equals 885 degree(s)C. SEM was used to inspect the surface morphology, Raman Spectroscopy to determine the quality, and XPS to analyze the chemical composition. It in concluded that a cleaning procedure on diamond surfaces can eliminate the carbon phase but enhance the oxygenation on the films. The electrical characteristics were investigated by current-voltage-temperature measurements in a metal-insulator-semiconductor (MIS) structure with top metal contacts and back silicon substrates contacts. It can be found a transition electric field of 240 kV/cm, where Schottky emission (SE) mechanism is responsible for electric conduction below 240kV/cm, and Poole-Frenkel transport (PF) mechanism dominates beyond 240 kV/cm. By the extrapolations, the Schottky barrier height of silver and diamond film is 2.4 eV, and the tarp depth is 4.75 eV in the diamond film.

In the past years, the aluminum nitride (AIN) thin films were usually applied to the surface acoustic wave (SAW) devices, optical devices in the ultraviolet spectral region, acousto-optic devices and integrated circuit packaging. In this study, we first selected the AIN thin film as gate insulator for pH sensing ISFET in our laboratory. We have studied the relationship between pH sensitivity and surface potential for AIN gate ISFET in the different solutions. And we also have obtained the pH characteristics from the capacitance-voltage (C-V) and current voltage (I-V) curves. Herein, we can obtain the shift of the linear region threshold voltage of the AIN/SiO₂ gate ISFET devices in the different buffer solutions. The AIN materials exhibited a high response, and the sensitivity was about 45~51 mV/pH. In addition, we have also compared with different sensing materials.

The role of temperature ramping rate during the two-step growth of GaN-on-sapphire by metalorganic chemical vapor deposition is explored. The surface morphology and crystalline properties of the GaN buffer layer annealed under various temperature ramping rates (20-60 degree(s)C/min) were investigated by atomic force microscopy and x-ray measurements. For the lower ramping rates employed, a dramatic re-evaporation of the GaN buffer layer was observed. This makes the buffer layer thinner, yielding the GaN epilayer of hexagonal morphology. However, as the higher ramping rates applied, the surface becomes rougher and exhibits hexagonal three-dimensional islands. It could be due to the fact that the grains of the GaN buffer layer have no enough time to course. Under a temperature ramping rate of 40 degree(s)C/min, a smooth buffer-layer surface can be maintained and result in a subsequent high-quality over- layer deposition. The mirror GaN epilayer shows a near-band- edge peak (25 K) centered at 3.477 eV with a full width at half maximum as narrow as 13.1 meV. The observed temperature-ramping-rate effects can be interpreted by the coalescence mechanism of the GaN buffer layer involving Ostwald ripening, sintering and cluster migration.

The effects of the exchange interaction between the localized d electrons of manganese ion and the delocalized host band electrons in II_1-xMn_xVI semiconductors are discussed based on the perturbation scheme and the k p theory as a function of the manganese composition. We observe that the exchange interaction lead to the red shift of the energy gap and it is shown that the many-body interaction due to exchange play an important role in accurate depiction of the energy gap with variation of the manganese amounts in diluted magnetic semiconductors. In addition, we have compared the results with experimental data of IR spectroscopy.

By using a phase-tunable optoelectronic phase-locked loop, we are able to continuously change the phase as well as the delay-time of optically distributed microwave clock signals or optical pulse train. The advantages of the proposed technique include such as wide-band operation up to 20GHz, wide-range tuning up to 640 degrees, high tuning resolution of <6x10^-2 degree/mV, ultra-low short-term phase fluctuation and drive of 4.7x10^-2 degree and 3.4x10^{- 3} degree/min, good linearity with acceptable deviations, and frequency-independent transferred function with slope of nearly 90 degrees/volt, etc. The novel optoelectronic phase shifter is performed by using a DC-voltage controlled, optoelectronic-mixer-based, frequency-down-converted digital phase-locked-loop. The maximum delay-time is continuously tunable up to 3.9 ns for optical pulses repeated at 500 MHz from a gain-switched laser diode. This corresponds to a delay responsivity of about 0.54 ps/mV. The using of the OEPS as being an optoelectronic delay-time controller for optical pulses is demonstrated with temporal resolution of <0.2 ps. Electro-optic sampling of high-frequency microwave signals by using the in-situ delay-time-tunable pulsed laser as a novel optical probe is primarily reported.

We present the high performance of InGaP/GaAs metal- semiconductor-metal photodetectors (MSM-PDs) using copper as the interdigital Schottky electrodes. The devices exhibit ultra-low dark current (70 pA at bias of 10 V) and ultra- fast pulse response (over 9 Ghz). The notable dark current characteristic and the absence of trap-induced gain are accredited to the superior properties of InGaP capping layer. The superior performances of InGaP/GaAs MSM-PDs make it promising for data communication.

The ED-Litho (Electrodeposition-Lithography) process is a unique method for making color filters, which combines electrodeposition of pigmented organic coating on ITO (Indium Tin Oxide) glass and a special photolithography technique based on a MDPR (MultiDeveloping PhotoResist). This process represents one of the potential methods to achieve low cost and high quality in the fabrication of color filter. This paper will report the related technologies and discuss the color performance used in TFT- LCD (Thin Film Transistor Liquid Crystal Display) panel.

This paper describes a low dielectric constant, high resolution and high brightness single layer positive photoresist on TFT array. A currently used positive photoresist comprising of low dielectric constant materials and a chemically amplified resis system is designed for the insulation layer on TFT array to enlarge pixel aperture ration of TFT-LCD.

A set of grating-frustrated directional couplers is proposed here for wavelength division multiplexer (WDM). Instead of using optical fiber, integrated polymer waveguides with inverted-ridge structure was used in this design. This device is composed of two cascaded directional couplers. Each of the directional coupler is made up of two waveguides with the index of one of the waveguides being a periodic function of z which is the direction of propagation. The average index of the grated waveguide should be equal to that of the un-graded waveguide. According to the coupled wave theory, only the light with a specific wavelength will pass through the waveguide without grating while all other light will be coupled to the grated waveguide when the mixed light is initially input at the un-grated waveguide. This phenomenon is call Bragg reflection and the specific wavelength is called Bragg wavelength. The Bragg wavelength is proportional to the period of the index grating. Therefore, this device is capable of selecting at least three different wavelengths. A detailed analysis of this design is also included in this paper.

A thin film waveguide of novel polymer Nylon 11 was fabricated and characterized. The active polymer waveguide film was formed by spin coating and poled by applying an electric field. The J-E and D-E curves with hysteresis characteristics of the Nylon 11 film was measured during poling, as well as the absorption spectrum of this waveguide film was observed by the FTIR before and after completing the poling. In addition, we have investigated the influence of the waveguide position and electrode structure on the optic axis distribution in the poled polymer film. The numerical results are given to establish a useful guideline for designing the poled polymer waveguide devices.

We study the island size distributions of Xi_1-xGe_x/Si(001) (x equals 0.4 - .07) islands of varying Ge fractions and thicknesses by ultrahigh vacuum chemical vapor deposition. The island size distributions of the percolating islands obey a dynamic scaling hypothesis admitting only one length scale governing the growth, in the limit of large island sizes. Although bimodal distributions are found in coherent islands at large misfit strain, due to the large stress concentration at island perimeters; faulted dislocation loops forming as islands grow remove this stress concentration. This re-establishes a unimodal distribution,, reclaiming the scaling hypothesis. We show that the misfit strain is renormalized and, thus, is not essential in determining the size distribution. We also demonstrate evidence for Smoluchowski ripening mechanism occuring during growth. Finally, we discuss implications of these issues on achieving a uniform Xi_1-xGe_x/Si(001) island distribution, which is crucial for technological applications.

A novel semiconductor/superlattice AlAs/[GaAs/AlAs] DBR has been obtained through replacing the Al_xGa_{1-x$As in the AlAs/Al(subscript x}Ga_1-xAs DBR with GaAs/AlAs superlattice. In experiment, a p-type of this kind of 19-period DBR has been grown by V80H MBE system. From the experimental reflection spectrum, the central wavelength of the DBP is about 850nm and the 19-period DBR has the reflectivity high up to as 99.5%. Moreover, by using twice self-designed tungsten filament mask and proton implantation method, the 10x10 (mu) m²square current flowing area has been made to measure the series resistance of the p-type DBR. The method can solve the difficulty in controlling the depth of etching prevent the occurrence of side etching in wet chemical etching usually used in experiments. From our experiment the series resistance of the DBR was just about 50 Ohms. Furthermore, the dependence of series resistance on temperature has also been studied. From the experimental results, it was found that the low series resistance of this kind of DBRs may be attributed to an increase in tunneling current on the semiconductor/superlattice minor structure that would leave to a decrease in the series resistance.

Integrated optical devices based on liquid crystal's (LC) features have been generally discarded for a long period mainly due to very high scattering losses. However, in the 90's this situation is rapidly changing. A better understanding of the physical phenomena underlying the observed effects, the use of new materials with improved performances, the discovery of new electro-optical and nonlinear optical effects make the applications of LC in integrated optics more and more attractive. We present here some recently obtained results in this field. In particular, we have designed and realized an integrated device in a three-stage planar waveguide, having as middle stage a nematic liquid crystal (NLC) film. We studied the device performance in different geometries using TE polarized light. By a proper choice of the material parameters we measured time responses in the microsecond rage. Our experimental results confirm the possibility of employing such a device working as an optical switch and/or beam deflector.

Photorefractive crystals have emerged as ideal candidates for storing large amounts of optical image information. According to the Band Transport model, photorefraction results from absorption at various impurity levels inside the crystal. Thus an understanding of impurity levels within a photorefractive crystal will facilitate further understanding of photorefraction. The Band Transport model assumes that the electrons in the conduction band are excited via optical transitions. There are shallow energy levels, however, which may also contribute conducting electrons via thermal excitation. We report here a method for estimating the location of shallow energy levels in a barium titanate crystal (dopes with 20ppm cobalt) by using two-wave mixing measurements at low temperatures. This method provides a lower limit of the location of the shallow energy level which is about 0.1 eV below the conduction in this crystal.

In this study, the commercial manufacture Beckman 110 (Si₃N₄ gate pH-ISFET) was acted as the sensitive membrane of pH-ISFET. The experimental results show that the Si₃N₄ material has a fairly high response, and the pH sensitivity was obtained at 56.94 mV/pH in a concentration rage between pH 1 and pH 11 at room temperature. In our experiment, we use Keithley 236 Semiconductor Parameter Analyzer to measure the drain current (I_DS) versus gate voltage (V_G) curve of Si₃N₄ ISFET over a pH range from 1 to 11 at room temperature. The constant voltage-current-circuit and time-voltage record were also used to measure the hysteresis curve of Beckman 110 (Si₃N₄ gate pH-ISFET). The same procedure was also applied to a-Si:H gate pH-ISFET, which fabricated in our laboratory. From the I_DS versus V_G and hysteresis curve, we can obtain that the pH sensitivity was 56.94 mV/pH at constant temperature (25 degree(s)C) and hysteresis widths of Beckman 110 (Si₃N₄ gate pH-ISFET) and a- Si:H gate pH-ISFET in the larger pH site are larger than in the smaller pH site, and the hysteresis width increased with the increasing loop time and measureing path.

In this study, we utilize the commercial device, Sentron 1090 Al₂O₃ gate pH-ISFET to study the sensitivity and hysteresis behaviour. The experimental results show that the Al₂O₃ materials have a fairly high response, and the sensitivity was obtained from the pH response of Sentron 1090. The hysteresis effect in a Sentron 1090 Al₂O₃ gate pH-ISFET was studied by exposing the device to two cycles of pH values. The hysteresis curves were measured in the sequence pH 8-3-8-11-8 and pH 7-3-7-11-7 at different loop time. According to experimental results, the hysteresis width is increasing with loop time and measuring path. We also observed and compared the pH sensitivity and magnitude of the hysteresis width with others pH-sensing gate ISFETs studied in our laboratory and the related literatures.

In application of the pH-ISFET, the hysteresis and temperature effects are two important influences of accuracy. There have been many studies about the above subjects, however, the hysteresis behaviour will change with the temperature and affect the reproducibility of the devices. Hence, we study the temperature dependence of the hysteresis behaviour for the pH-ISFET with a-Si:H gate insulator deposited by the PE-LPCVD system in this paper. The thickness of the a-Si:H was about 2000 A. The temperature is controlled by the P.I.D. temperature controlled system and the hysteresis behaviour is measured by the constant voltage-constant current circuit and voltage-time recorder. The measurement is completed at 25 degree(s)C, 35 degree(s)C, 45 degree(s)C and 55 degree(s)C and the time after the pH changed is 4 min, The experimental results also compared with other materials of the gate insulator for pH-ISFET at the room temperature.

Phase conjugate phenomenon and mechanism with BaTiO₃ photorefractive crystals have been investigated using various cw sources and all the way down with ultrashort pulses of the femtosecond region. Our laser sources support all the various pulsewidths at a wide range of different spectral regions.

As we approach the new millennium, the ongoing aim of human society is not only for promoting scientific technology but also creating new industries. To achieve this goal, each person in industry must recognize anew that the real meaning of science is to explore the absolute truth. It is also important that people recognize that there are unlimited matters which we humans do now yet know.