The beam quality of weakly index-guided edge emitting 980nm lasers is investigated via time-resolved far-field measurement technique. A synchronous detection scheme is used to directly measure lasers' far-field pattern, intensity versus divergence angle, as functions of duration and amplitude of injection current pulses. It is shown that the degradation of beam quality, characterized as multiple lateral modes and observed as beam steering of far-field pattern, highly depends on the transient condition associated with the duration of injection current pulses. The beam steering of far-field pattern is well correlated to the kink in power-versus-current curve under the same transient condition. We experimentally found that time constant for the far-field pattern to reach steady state is ~1.4 microsecond. From thermal transience modeling, we conclude that beam steering is the result of local heating, which produces a lateral temperature gradient profile at the laser waveguide region to significantly enhance the lateral index contrast.

The electronics structures of the Ga_1-xIN_xN_yAs_1-y/GaAs compressive strained quantum wells(QWs) are investigated using 6x6 kxp Hamiltonian including the heavy hole, light hole and spin-orbit splitting band. By varying the well width and mole fraction of N in the well material, the effects of quantum confinement and compressive strain are examined. The curves of dependence of transition energy on well width and N mole fraction are obtained. The valence subband energy dispersion curves, density of states, TE and TM squared optical transition matrix elements and optical gain spectra of three possible quantum well structures for emitting 1.3micrometers wavelength are given.

Within the last few years, high power laser diodes with remarkable improvements concerning output power, efficiency, and reliability have been investigated in the wavelength range between 780 nm and 1064 nm. A lot of the work has been focused on 980 nm, the pump wavelength of Erbium Doped Fiber Amplifiers (EDFAs). Pumping of EDFAs requires highest performance diode lasers due to extreme demands in reliability and beam quality. Up to now, the only type of diode laser used in this application is a single-stripe or ridge-laser which emits in a diffraction-limited optical mode and can therefore be coupled into a single-mode fiber with high efficiency. The small stripe-width limits the reliable output power of these devices to about 300 mW resulting in a fiber coupled output power of less than 250 mW. In the following we report on high-power 980 nm diode lasers comprising ridge and tapered sections for near diffraction limited output power in the watt regime. The devices are based on MBE grown layer structures in the AlInGaAs material system. They allow for more than 500 mW of optical power coupled into a single mode fiber. First reliability tests show extrapolated lifetimes of more than 7.500 h at an output power of 1.8 W.

For increasing laser diode (LD) output power, improving laser beam quality and enhancing the light emitting diode (LED) brightness, the coupled large optical cavity semiconductor lasers and multi-active LEDs with tunneling- regenerated current transport have been presented and experimented. Both the external and differential quantum efficiency and both the LD's output power and LED's brightness are together increasing approximately with the number of the active regions. The very high power Lds and and the very high brightness LEDs working the low injecting current and also the fundamental mode stimulated light with good beam quality have been achieved in our laboratory.

High speed reliable 1550nm AlGaInAs multi-quantum well ridge waveguide (RW) DFB laser is developed with a 9GHz ¿C3dB bandwidth. A high speed self aligned constricted mesa 1550nm DFB laser is achieved with a 9.1GHz ¿C3dB bandwidth and a more than 20mW output power. A cost effective single RW electroabsorption modulated DFB laser (EMLs) is proposed and successfully fabricated by adopting selective area growth techniques; a penalty free transmission at 2.5Gbps over 280Km normal G.652 single mode fiber is realized by using this EML as light source. For achieving a better performance EMLs, a gain-coupled DFB laser with etched quantum wells is successfully integrated with a electroabsorption modulator (EAM) for a high single mode yield; the wavelength of a EML is tuned in a 3.2nm range by a integrated thin-film heater for the wavelength routing; a buried heterostructure DFB laser is also successfully integrated with a RW EAM for a lower threshold current, lower EAM parasitic capacitance and higher output power.

We use empirical equations verified indirectly by experimental results in first priority to calculate band lineup and other parameters related to optical gain calculations for strained InGaAsP/InP quantum well (QW) structures, the parameters without such known empirical equations are calculated by interpolation scheme from binary or ternary compound that consists the quaternary alloys. This approach may sacrifice the systematical feature but the results are more accurate.

Wavelength-tunable lasers, detectors, and optical filters are expected to play a pivotal role in the future ultrahigh bandwidth dense-wavelength-division-multiplexed (DWDM) optical networks, enabling revolutionary new applications such as wavelength-on-demand in a reconfigurable all-optical network. Combining the unique single wavelength property of a vertical cavity and the wide mechanical movement of a MEMS mirror, we are able to demonstrate photonic devices with a very wide tuning range and excellent performance. Electrically-pumped, continuously tunable VCSEL emitting in 1530-1620 nm wavelength regime is reported. The VCSELs exhibit a continuous, repeatable and hysterisis-free wavelength-tuning characteristic. Further, the VCSELs are directly modulated at 2.5 Gbps and has >45 dB side mode suppression ratio (SMSR) over the entire tuning range. Accurate wavelength locking is achieved in ~200 usec by a simple universal locker.

In this paper, we will present the results of the 850nm implanted and oxide-confined vertical cavity surface emitting lasers in multi-Gigabit application. In TrueLight, we have a lot of experience in manufacturing VCSEL with ion-implantation and wet-oxidation technologies for single device Gigabit data transmission application. The ion-implanted VCSEL is reliable with the Mean Time To Failure (MTTF) up to 108 hours at room temperature operation. For the gigabit Ethernet data communication, it provides a very promising solution in short haul application. In transmission experiment we demonstrated the devices could be modulated up to 2.5Gbps and 3.2Gbps data rate. For oxide-confined VCSEL devices, we use wet oxidation technology to approach the device processing and get very good result to achieve the mutli-gigabit data communication application in single device form. The VCSEL device with oxide aperture around 12um could be modulated up to 2.5Gbps and 3.2Gbps. A data of employing VCSEL in high data rate POF transmission is also presented.

Electron and hole diffusions in the plane of semiconductor quantum wells play an important part in the static and dynamic operations of semiconductor lasers. In this paper, we apply a hydrodynamic model developed from the semiconductor Bloch equations to numerically study the effects of nonlinearity in the diffusion coefficient on single mode operation and direct modulation of a gain-guided InGaAs/GaAs multiple quantum well laser, operating not too far from threshold. We found that a small diffusion coefficient is advantageous for lowering the threshold current and increasing the modulation bandwidth. Most importantly, the effects of nonlinearity in the coefficient can be approximately reproduced by replacing the coefficient with an effective constant diffusion coefficient, which corresponds roughly to the half height density of the density distribution. This conclusion is the same as in Ref. 8, but we will discuss the disagreements in reaching it. Finally, the beam profile is slightly modified in the nonlinear case.

We report some investigations on vertical cavity surface emitting laser (VCSEL) arrays and VCSEL based optoelectronic smart photonic multiple chip modules (MCM), consisting of 1x16 vertical cavity surface emitting laser array and 16- channel lasers driver 0.35 )mum CMOS circuit. The hybrid integrated multiple chip modules based on VCSEL operate at more than 2GHz in-3dB frequency bandwidth.

We have proved that short cavity length and large optical feedback structure can improve the relaxation oscillation frequency (fr) of 1.3mm directly modulated LDs for 10Gb/s operation. By this improvement, 1.3mm InGaAsP l/4 phase shifted distributed-feedback LDs (l/4 DFB-LDs) and 1.3mm AlGaInAs Fabry-Perot (FP)-LDs successfully revealed excellent transmission with small power penalty of 0.6dB at 70 oC for +40ps/nm wavelength dispersion and 1.5dB at 85oC for +10ps/nm one, respectively. It has been also proved that 1.55mm electro-absorption modulator integrated with DFB-LDs (EAM DFB-LDs) with MQW absorption layers are more suitable for 100km transmission than those with bulk ones, which originates from the difference of extinction curves. Transmission characteristics using 100km SMF of 1.55mm EAM DFB-LD with an MQW absorption layer has been realized with power penalty of 1.3dB. These devices can cover all optical lines of various distances in metropolitan area networks.

The growth of GaInNAs/GaAs quantum well (QW) has been investigated by solid-source molecular beam epitaxy (MBE). N was introduced by a dc-active plasma source. Highest N concentration of 2.6% in GaInNAs/GaAs QW was obtained, corresponding to the photoluminescence peak wavelength of 1.57 (m at 10K. The nitrogen incorporation behavior in MBE growth and the quality improvement of the QW have been studied in detail. 1.3 (m GaInNAs/GaAs SQW laser and MQW resonant-cavity enhanced photodetector have been achieved.

The optimization of wavelength detuning for better transmission capability in an identical expitaxial layer (IEL) integrated light source is presented. The absorption spectra of the multiple-quantum-well (MQW) material under varying electric fields are worked out by using the fractional dimensional method. The extinction ratio and the chirping parameter of a 200um-long modulator section are calculated accordingly for different working wavelengths. A voltage-related chirping parameter has been used in a 10Gb/s-transmission simulation to make a more realistic description of the performances of the EA modulator in actual fiber communication systems. A detuning value of about 30~50nm is found to be the optimum in the sense of low power penalty and high sensitivity according to the simulation results.

With fiber optical telecommunication systems penetrating into metropolitan and access networks, planar waveguide technology is increasingly being considered a solution to the bottleneck of cost-effective manufacture of passive components. Being recognized for their high thermo-optical coefficient, ease of fabrication, cost-effectiveness, good compatibility with other materials, polymer as a platform technology for waveguide devices is gaining more and more commercial acceptance. Fully exploiting the potentials of the polymeric materials demands comprehensive understanding of both the specific device applications and various polymer systems. The right choice of materials is often the key to the success of component development. Unfortunately, since extensive study on polymeric materials and devices operating at 1.55 micrometer just began recently, few ideal materials have been so far made commercially available. From the polymer chemistry point of view, it is possible to tailor the materials meeting specific and strict requirements for optical waveguide devices. The present author reviews the most promising fluorinated polymers and silicone resins and their demonstrated device applications. The paper is designed for providing guide to both polymer scientists, who want to develop novel high performance materials for waveguide applications, and optical engineers who need to gain insight of the materials.

A novel photonic functional device, a rectangle variable optical filter using dynamic grating in Er doped fiber (EDF) controlled by synthesis of optical coherence function, is proposed and analyzed. Due to the gain saturation of EDF, a periodic bleaching of the gain (dynamic grating) is generated, when an intensity standing wave is produced by interference of two laser beams traveling in EDF with opposite directions. When the frequency of the laser is modulated with an appropriate waveform, shape of the optical coherence function can be synthesized. It can be used to control the interferometric pattern in the EDF, and then the dynamic grating can also be controlled. Thus, the shape and bandwidth of the reflection spectrum of the dynamic grating becomes controllable. Simulations indicate that the spectrum of the filter can be controlled by synthesis of optical coherence function. Preliminary experiment confirmed the principle.

Current development of optical network component devices has increased demand for various optical and opto-electronic materials for a wide range of applications such as switches, waveguides, amplifiers, Bragg gratings, splitters, isolators circulators, lasers and detectors. Furthermore, low cost manufacture of component devices demands higher and higher integration of individual components onto a small, planar foot print. One of the major issues with optical integration is that various optical functionalities come from materials with different compositions. As a result, it is highly desirable to have a means to produce high quality optical materials with various compositions, and to deposit them onto a common substrate. We present in this paper a novel nanoscale materials synthesis method to produce optical materials in nanoscale particulate form, which can subsequently deposited onto a substrate at a high deposition rate. Further treatment of these materials on the substrate can be used to transform these nanoscale particle building block into dense solids to achieve optical functional properties such as optical transparency, amplification or UV sensitivity.

No annealed, annealed after growth and annealed during growth ZnO films (denoted s1,s2, and s3 respectively) were grown on C-plane sapphire substrate by plasma-enhanced MOCVD and characterized by XRD and the optical transmission spectra. We could find that there is tensile strain in the c-plane of the films. Furthermore, the tensile strain increases after annealing. At the same time, the optical transmission indicates that the transmission of s2 in visible region is the highest and the value of s3 is the lowest.

A novel approach to achieving a polarization-insensitive semiconductor optical amplifier is presented. The active layer consists of graded tensile strained bulk-like structure, which can not only enhance TM mode material gain and further realize polarization-insensitivity, but also get a large 3dB bandwidth due to different strain introduced into the active layer. 3dB bandwidth more than 40nm, 65nm has been obtained in the experiment and theory, respectively. The characteristics of such polarization insensitive structure have been analyzed. The influence of the amount of strain and of the thickness of strain layer on the polarization insensitivity has been discussed.

Gain saturation and the induced refractive index variation in semiconductor optical amplifiers (SOAs) have been widely used for many optoelectronics operations, including frequency conversion, phase conjugation, switching, modulation, and laser mode locking. In this paper, we report the experimental and numerical results of using gain saturation in SOAs for all-optical switching and novel laser mode locking configurations. For all-optical switching, we fabricated an all-SOA nonlinear optical loop mirror and implemented efficient power-dependent switching in both cw and pulse modes. Also, numerical modeling was also conducted to show consistent trends with experimental data. For novel laser mode-locking configurations, we demonstrated numerically efficient operation of mode-locked semiconductor laser with multi-mode interference SOA structures. With the nonlinear coupling process, it was found that efficient pulse compression could be achieved, implying that stable mode locking is feasible. Also, with a ring cavity colliding-pulse mode locking can be implemented.

A new optoelectronic integrated device composed of an Optical Field Effect Transistor (OPFET) in series with a double heterojunction light emitting diode (LED) or a laser liode (LD) which can be used as a Light Amplifying Optical Switch (LAOS), is presented in this paper. We shall call this device as OPFET-LAOS since it is a new one in its category. Theoretical investigation has been carried out to develop the I-V characteristic of the proposed device. It is shown theoretically that the device changes its state form a low current (i.e. high impedance) state to a high current (i.e. low impedance) state through a region of negative differential resistance (NDR) when the applied voltage exceeds a certain limit, called the breakover voltage. Thus, the I-V characteristic of the device is similar to that of an existing LAOS composed of a heterojunction phototransistor (HPT) in series with a double heterojunction LED (or LD).

In this communication, we demonstrate experimentally a new design for all-optical AND and NAND gates operating in the GHz regime using the cross-polarization modulation effect in a semiconductor optical amplifier. The efficiency of this effect was estimated by measuring the conversion coefficients indicating the TE to TM mode conversion and vice versa when the amplifier is perturbed with a wavelength tunable control beam. The all-optical gates here described differ from other ones developed before using semiconductor optical amplifiers by their ability to operate on non-degenerate input signals with an output signal wavelength independent of the input signals wavelength.

The first method for distributed fiber measurements was the optical-domain reflectometry. This method used backward Rayleigh scattering to observe the optical loss along the fiber. Distributed temperature and strain measurements can be realized by using stimulated Brillouin scattering. This effect can be described s three-wave interaction of pump laser wave, a Stokes wave and an acoustic wave of characteristic Brillouin frequency. This frequency depends on temperature and strain. This effect was used for distributed measurements and realized in Brillouin optical time-domain analysis. Brillouin optical frequency-domain analysis is discussed. In the method, the continuous wave light of narrow linewidth pump laser is coupled into one end of the sensor fiber and a sinusoidal modulated intensity of a probe laser is coupled to the other end. If the frequency difference between both lasers equals to characteristic Brillouin frequency, the pump light will interact with the modulated prove light in the fiber. By analyzing the transmitted pump intensity at different frequency difference between probe and pump lasers, the temperature and strai distribution along the fiber can be determined. By analyzing the dependence of transmitted pump intensity on frequency difference the magnitude of temperature and strain is determined. Numerical simulation of a Brillouin optical frequency-domain analysis is represented. In this numerical simulation several fiber lengths with different but spatial constant gain coefficients were placed one after another. For each fiber part the fundamental oscillation of the transmitted pump intensity is calculated by the derived analytical expression with respect to individual Brillouin gain coefficients. The DC components of the input pump and stokes powers of each region are determined by numerical iteration. Alternating part of pump intensity is assumed not to interact with to interact with Stokes power because it is very week. Only the DC component of the pump power produces Brillouin interaction. Considering the phase shift of the transmitted alternating components of the pump powrs of each different located fiber regions, the baseband modulation transfer function is calculated. In the modulation a 944-m- length single-mode fiber was considered. It has two regions (length 20 m and 1.5m) of higher temperature (T=78C) than that of the unheated fiber, which had a temperature of 26 C, and 50-m and 3-m-long regions of higher strain (e=0.1%). The unheated and unstrained parts of the fiber had a characteristic Brillouin frequency of 12.8 Ghz. The characteristic Brillouin frequencies of heated and stained regions were 12.86 GHz and 12.85 Ghz. If the frequency is near 12.8GHz, Brillouin interaction and loss of the pump wave only in the undisturbed regions will be observed. With increasing frequency difference, the Brillouin gain coefficient in the undisturbed fiber will be reduced. The Brillouin gain coefficient in the strained regions will be increased because the frequency difference between the pump and probe lasers approaches the characteristic Brillouin frequency of these regions. At the frequency difference of 12.83GHz Brillouin loss of the pump wave are observed in the heated fiber parts. The maximum interaction in the strained regions will be reached, if the frequency difference amounts to 12.85GHz. Then it will be reduced and when the frequency difference with reach 12.86GHz, maximum interaction will be reached in heated regions.

The quantum well intermixing of Ga(In)NAs/GaAs simple quantum well (SQW) using SiO2 encapsulation and rapid thermal annealing has been studied. Obvious enhanced intermixing of GaInNAs/GaAs SQW was observed due to the localized SiO2 capping layer and RTA at temperature between 650íµ and 900íµ. The selective intermixing strongly depends on N composition and In composition. An obvious selective intermixing had been found in the samples with small N composition and/or high In composition.

In this article, the transfer matrix method (TMM) is modified for study of optical wave propagation in layered media with conducting interfaces. Both the TE and TM mode transfer matrices are derived and their properties are discussed.

An envelope ADI-FDTD technique is proposed and developed based on recently published ADI-FDTD method. Compared with FDTD and ADI-FDTD, the proposed method significantly reduces the computation time while retaining reasonable accuracy. Perfectly Matched Layer (PML) boundary condition is successfully used in conjunction with the envelope ADI-FDTD. Demonstrations of the method are performed on various high index contrast structures including 90-degree waveguide bends, air-hole photonic band-gap structures and microdisk resonators.

Optical properties and growth of self-assembled quantum dots (SAQDs) for optoelectronic device applications are discussed. After briefly reviewing the history of research on QD lasers, we discuss growth of InAs SQDs including the light emission at the wavelength of 1.52)mum with a narrow linewidth (22 meV) and the area-controlled growth which demonstrates formation of SAQDs in selected local areas on a growth plane using a SiO)-2) mask with MOCVD growth. Then properties of the InGaAs AQDs are investigated by the near- field photoluminescence excitation spectroscopy which reveals gradually increasing continuum absorption connected with the two-dimensional-like (2D-like) wetting layer, resulting in faster relaxation of electrons due to a crossover between OD and 2D character in the density of states. Moreover, we have investigated InGaN self-assembled QDs on a GaN layer achieving the average diameter as small as 8.4nm and a strong light at room temperature. A laser structure with the stacked InGAN QDs embedded in the active layer was fabricated and room temperature operation of blue InGaN QD lasers was achieved under optical excitation. Carrier confinement in QDs was examined using near-field $DAL- photoluminescence measurement: A very sharp spectral line emitted from excitons in individual InGaN QDs was observed. Establishing AlGaN/GaN DBR of high quality, we succeeded in lasing action in InGaN blue light emitting VCSELs. Enhancement of spontaneous emission is demonstrated. Finally, perspective of QD lasers.

The semiconductor microlasers based on the equilateral triangle resonator (ETR) can be fabricated from the edge-emitting laser wafer by dry-etching technique, and the directional emission can be obtained by connecting an output waveguide to one of the vertices of the ETR. We investigate the mode characteristics, especially the mode quality factor, for the ETR with imperfect vertices, which is inevitable in the real technique process. The numerical simulations show that the confined modes can still have a high quality factor in the ETR with imperfect vertices. We can expect that the microlasers is a suitable light source for photonic integrated circuits.

The development of Si-based photodetectors is very important due to their compatibility with the state-of-the-art Si planar technology. Photodetectors based on Ge quantum dots were studied. Three p-i-n structures containing Ge dots were grown by molecular beam epitaxy in Stranski-Krastanov mode. The dots were grown embedded in Si spacing layers on Si (100) substrates. The nominal Ge growth thickness in each layer was 1.2, 1.5 and 1.8 nm for the three samples, respectively. Photoluminescence measurement showed that the Ge dot related peak shift to lower energy with increasing the dot layer thickness. The materials were processed into p-i-n photodiodes with conventional processing methods. I-V measurement showed a low dark current density of 3x10-5A/cm2 at -1 V. A strong photoresponse at 1.3-1.55 mm originating from Ge dots was observed. The response peak shifts with the Ge growth thickness. At normal incidence, an external quantum efficiency of 8% was achieved at 2.5 V. The dot layers were considered to trap the light in the intrinsic region, and thus increase the absorption.

We show that the observed temperature dependence of the photoluminescence(PL) features can be consistently explained in terms of thermally activated carrier transfer processes in a multilayer structure of the self-organized Ge/Si(001) islands. The type II (electron confinement in Si) behavior of the Ge/Si islands is verified. With elevated temperature, the thermally activated electrons and holes enter the Ge islands from the Si and from the wetting layer (WL), respectively. An involvement of the type I (spatially direct) into type II (spatially indirect) recombination transition takes place at a high temperature.

The concept and analyzing method of photonic crystals and band gap were introduced into optical holography. Volume holograms were treated theoretically as a photonic crystal. All properties of volume holograms can be explained accurately with the band structure of photonic crystal. Different from superlattice photonic crystal, the inductivity of holographic photonic crystal is a graded function rather than a discontinuous function, the band gap structures with changing incident angle (not for a fixed angle only) were discussed. Experimental verifications were implemented by using elementary reflection holograms. It shows that the analysis of band gap for volume holograms is in good consistency, with the experimental results.

Epitaxial lateral overgrowth (ELO) of GaN on SiO2 masked (0001) GaN substrate has been investigated by using chloride-based growth chemistries via hydride vapor phase epitaxy and metalorganic vapor phase epitaxy with diethylgallium chloride as the Ga source. It has been found that both the lateral and vertical growth rate, and geometric morphology of lateral overgrown GaN prisms are dependent on growth conditions (growth temperature and V/III ratio) and orientations. A high growth temperature and low V/III ratio is helpful to increase the lateral growth rate and flatten the top c-plane of GaN prisms. High quality coalesced flat-top ELO GaN has been fabricated by HVPE and no void is observable at the coalescence interface.

Planar punch through heterojunction phototransistors with a novel emitter control electrode and ion- implanted isolation (CE-PTHPT) are investigated. The phototransistors have a working voltage of 3-10V and high sensitivity at low input power. The base of the transistor is completely depleted under operating condition. Base current is zero. The CE-PTHPT has an increased speed and a decreased noise. The novel CE-PTHPT has been fabricated in this paper. The optical gain of GaAlAs/GaAs CE-PTHPT for the incident light power 1.3 and 43nw with the wavelength of 0.8μ+m reached 1260 and 8108. The input noise current calculated is 5.46*10^-16 A/Hz^1/2. For polysilicon emitter CE-PTHPT, the optical gain is 3083 at the input power of 0.174μ+w. The optical gain of InGaAs/InP CE-PTHPT reaches 350 for an incident power of 0.3μ+w at the wavelength of 1.55μ+m. The CE-PTHPT detectors is promising as photo detectors for optical fiber communication system.

A GaInNAs/GaAs multiple quantum well (MQW) resonant-cavity enhanced (RCE) photodetector operating at 1.3 μm with the full-width at half-maximum of 5.5 nm was demonstrated. The GaInNAs RCE photodetector was grown by molecular-beam epitaxy using an ion-removed dc-plasma cell as nitrogen source. GaInNAs/GaAs MQW shows a strong exciton peak at room temperature that is very beneficial for applications in long-wavelength absorption devices. For a 100-μm diameter RCE photodetector, the dark current is 20 and 32 pA at biases of 0 and 6 V, respectively, and the breakdown voltage is -18 V. The measured 3-dB bandwidth is 308 MHz. The reasons resulting in the poor high speed property were analyzed. The tunable wavelength of 18 nm with the angle of incident light was observed.

The two-color detection using the multiple quantum well infrared photodetector consisting of InGaAs/GaAs step quantum wells with AlGaAs/GaAs superlattice barriers is investigated. The bound-to-bound and bound-to-continuum transitions in the step quantum wells provide two responses with energy separation large enough for the dual-band detection in the mid- and long-wave infrared ranges. The photocurrent due to the bound-to-bound transition can be extracted with a low external electric field via the miniband in the superlattice barriers so that the high leakage current is avoided. The Stark's shifts caused by the coupling and separation of energy states were clearly observed and the relevant analysis is discussed. This work demonstrates the use of asymmetric quantum wells with superlattice barriers for the fabrication of multicolor infrared detectors.

Si-based SiGe/Si strained MQW long-wavelength photodetectors (PD) with cycle type (Ring Shape) waveguide (CWG) and resonant-cavity-enhanced (RCE) structure have been investigated for the first time for improving the quantum efficiency and response time. The results show that the responsivities are higher than that of conventional PD with a same Ge content reported previously. In addition, RCE-PD has an obvious narrow band response with FWHM less than 6nm.

SiO₂:Si:Er films were deposited on n⁺-Si substrate using the magnetron sputtering technique, and then Au/ SiO₂: Si:Er /n⁺-Si diodes were fabricated. Both Er³⁺ photoluminescence (PL) from the SiO₂: Si: Er/n⁺-Si and electroluminescence (EL) from the Au/SiO₂: Si: Er /n⁺-Si diodes were studied. The 1.54 micrometers PL intensity ratio of SiO₂: Si: Er/n⁺-Si to that of the SiO₂: Er/n⁺-Si measured under identical conditions can be as large as ~30. While the 1.54 micrometers EL intensity ratio of an Au/ SiO₂:Si:Er/n⁺-Si diode to that of an Au/SiO₂:Er/n⁺-Si diode measured under identical conditions can be as large as 6. We also deposited nanoscale (SiO₂:Er/Si(1.0~4.0nm)/SiO₂:Er) sandwich structure, in which the silicon layer between the two SiO₂:Er barriers was 1.0~4.0 nm thick with an interval of 0.2 nm, on both n⁺-Si and p-Si substrates. Each EL spectrum of the Au/nanoscale (SiO₂:Er/Si/SiO₂:Er)/n⁺-Si diodes can be fitted by three Gaussian bands with peak energies of 0.757 eV (1.64 micrometers ), 0.806 eV (1.54 micrometers ) and 0.860 eV (1.44 micrometers ), and full widths at half maximum of 0.052, 0.045 and 0.055 eV, respectively. Among the Au/nanoscale (SiO₂:Er/Si/SiO2:Er)/n⁺-Si diodes with the Si layers having various thicknesses, the EL intensities of the 1.64, 1.54 and 1.44 micrometers bands of the diode with a 1.6 nm Si layer attain maxima which are 22, 8 and 7 times larger than those of the control diode without any Si layer (Au/nanoscale SiO₂:Er/n⁺-Si), respectively.

SiO2 thick films were deposited on silicon wafer (2 inches in diameter) as buffer layer for fabricating planar optical wave-guide by flame hydrolysis deposition (FHD) method. The deposition speed is as high as 8μ+m per minute. Then the deposited films were consolidated in electric furnaces in vacuum or air ambience at the temperature of 1380°C. As a result, transparent vitreous silica (or called silica glass) and semi-transparent cristobalite films were obtained. The thickness of the vitreous silica films is up to 40μm, and this kind of films is suitable for buffer layer of planar wave-guide. SiO2 thick films doped with GeO2 were obtained by the same process to fabricate the core layer. Finally, several factors affecting the consolidated silica films were discussed in detail.

Surface micromachining processes based on III-V compound semiconductors are presented in this paper, in order to develop Micro-Opto-Electro-Mechanical systems (MOEMS). By fabricating micro cantilevers composed of seven InP/Air gap pairs, the major techniques of the surface micromachining are studied, including non-selective and selective etching, rinsing and drying. A severe problem of the sticking phenomena during rinsing and drying is avoided by the implementation of the Critical Point Drying (CPD) method.

This paper presents an overview of our study on the study on the subject that is categorically termed <<microphotonics>>. Microelectronics, as we define it here, is an area of scientific and technological study concerning the miniaturization, interconnection, and integration of photonic devices, circuits, and systems in micron or submicron scale. We examine the scientifc and technological issues relating to these matters and discuss the challenges that the microphotonics faces toward the information technology in the 21st century. In the course of this study, we closely follow the experiences of microelectronics side by side, so that they can provide lessons, learnings, and insights that microphotonics can rightfully benefit from in a complementary form. Similarities, dissimilarites, advantages, and disadvantages, merits and demerits of the two technologies are explored in such a way that they can be more effectively utilized by mutual support.

We propose a novel 10-GHz-order frequency shifter using Bragg diffraction in electro-optic traveling phase grating with slant-stripe-typed periodic domain inversion. The principle of frequency shift is same as acousto-optic frequency shifter. However, no electro-optic frequency shifter in 10-GHz-order or less using Bragg diffraction has been developed so far because the wavelength of electromagnetic wave is too long to cause Bragg diffraction. Our new frequency shifter has the feature that spatial period of the phase grating does not depend on not the wavelength of modulating microwave but the period of domain inversion. Therefore, the period of the phase grating small enough to cause Bragg diffraction is possible in the frequency range of over 10 GHz by using our new device. Simulation results from Beam Propagation Method indicates that only the first-order diffraction occurs at the output end of this device, and the optical frequency is shifted by modulating microwave frequency.

Theory of acousto-optic coupling ring resonators is investigated in this thesis, and such a fiber ring resonator is based on the acousto-optic fiber couplers special characteristics---frequency-shift and filtering. In the resonant cavity, this kind of resonator will build up multiple-beam interferometry with frequency shift. Such a resonator can convert continuous wave laser to pulse train.

Some aspects of growth of volume nonlinear-optical KTP and BBO single crystals, specific features of formation of their real structure and its characteristics have been studied. They can be governed by such phenomena as formation and restructuring of adsorption layers at the interface of crystal growth, their possible directing and screening effect on solution-melt clusters, mechanism of formation of the polarity of crystal structure, etc. The most important factor is the tendency to form antipolar structures of these crystals, caused by internal energy reasons. It is shown that for developing efficient technological processes for production of this type of crystals, in addition to the above factors, real processes of temperature-time changes in structure and properties of complex solution-melt crystallization media must be also taken into account.

A future polymer based electro-optical (EO) modulator has several advantages over a current commercial Lithium Niobate EO modulator, a key device that encodes electronic signals into optical signals. These advantages include larger bandwidth (over 100 GHz), lower drive voltage (less then 1 volt), more cost effective, etc. However, one major challenge for EO polymer development is materials stability, including short term and long term SHG (NLO chromophore orientation) stability. Since the modulator fabrication and packaging processes typically require heating temperatures of 200-250oC for up to 10 minutes, yet the SHG thermal stability of most NLO polymers developed so far only reach about 150oC. In order to overcome this challenge, either modulator processing temperatures are reduced, or SHG thermal stability of EO polymers be increased. Polymer crosslinking technique is one of the most versatile and effective methods for fabricating and stabilizing polymer nano structures at high temperatures. Among various NLO polymer crosslinking schemes developed so far, fumaryl chloride (FC) and maleic anhydride (MA) derived crosslinked polyester system seems to be a versatile and convenient scheme. This scheme also looks attractive for low loss applications at 1550 nm. FC/MA crosslinking systems also offer visible light photolithographic fabrication advantage during waveguide fabrication.

An organic quantum-well structure electroluminescent device is fabricated by a doping method. The quantum-well structure consists of (formula available in paper) as potential well and emitter, undoped NPB as a barrier potential. Compared with a conventional doping structure device, both the maximum brightness and electroluminescent (EL) efficiency of the device are enhanced, reaching 40 000 cd/m2 and 5.6 cd/A, respectively. Especially, with the increase of the drive voltage, the EL efficiency (cd/A), after reaching its maximum, declines very slowly, almost independent of the drive voltage in a wide range from 5V to 13V. The characteristic may be useful in improving the lifetime of the device.

Some novel multi-dimensional charge-transfer (CT) chromophores, 2-[4-(4,5-di(4-nitrophenyl) imidazolyl)phenyl]-4,5-di(4-aminophenyl)imidazole (DNPIPDAPI), 2-[4-(4,5-di(4-nitrophenyl)imidazolyl)phenyl]-4,5-di(4-metho xy phenyl)imidazole(DNPIPDMOPI) and 2-[4-(4,5-di(4-nitrophenyl) imidazolyl) phenyl]-4,5-di(4-hydroxy-phenyl) imidazole(DNPIPDHPI) were designed and synthesized. And the polyimide was formed with one of the novel chromophores(DNPIPDAPI) and (formula available in paper). The thermal and temporal stability of the poling induce orientation were evaluated. The temporal orientation of the poled polyimide film with DNPIPDAPI was over 1000 hours at 150°C retaining 85% of the initial d33value. Comparing with 1-D chromophores, the synthetic multiple CT chromophore possesses better property in controlling the decay of the SHG activity.

We have used spectroscopic ellipsometry (SE) to determine the optical functions of PTCDA. The samples have been prepared by thermal evaporation of PTCDA on quartz glass substrates. We have also investigated influence of the substrate temperature to the properties of PTCDA films. We have found that the surface roughness of the films, determined by atomic force microscopy, increases with the increase of substrate temperature. The lowest substrate temperature investigated here is the room temperature. At room temperature and higher substrate temperatures we have not observed ordering of the evaporated films (ordering would result in high anisotropy) which has been reported for PTCDA films grown by organic molecular beam deposition at very low temperatures (so called quasi-epitaxial growth). Therefore, the samples have been assumed to be isotropic. The obtained imaginary part of the dielectric function exhibits the expected features, i.e. low magnitude peak around 370 nm and higher magnitude two peak structure in 400-600 nm spectral region. The dielectric function spectra of the samples grown at room temperature and at 100#C have been compared and discussed.

The optical nonlinearity of (TBA)2Ni(dmit)2 (TBA = tert-n-butanyl-amonimium, dmit = 1,3-dithiol-2-thione-4,5-dithiolate) at high incident irradiance was investigated using Z-scan technique with 1064 nm picosecond laser pulses. This molecule shows a strong absorption band ranging from 900 to 1600 nm. Under excitation by 1064nm laser pulses, this molecule exhibits typical saturable-absorption (SA) due to this transition, and shows a negative third-order contribution to nonlinear refraction (NLR). This result indicates that it shows a third-order self-defocusing. In addition, a positive fifth-order contribution to NLR, and the influences of aggregation and high excited-state absorption on nonlinear absorption were also observed in this molecule.

Some of cyanine dyes and ionic functional chromophore have been widely used to probe the conformation of DNA helix through measurement of induced circular dichroism (CD) spectrum, change of UV-visible spectrum and enhancement of fluorescence. In order to develop new type optical and optoelectric materials we studied the interaction between a hemicyamnine dye and DNA in aqueous solution and have prepared the NLO dye-DNA complex films. We first found that binding of the famous NLO dyes, C22HEMI to DNA induced strong CD band in the absorption spectra of the dyes in DNA aqueous solution and DNA-CTMA complex film1. The enhancement of the fluorescence quantum yield upon binding of the dye to DNA in aqueous solution is above 100-fold. Luminescence of the hemicyanine dyes-doped in DNA-CTMA film displayed enhancement fluorescence above three orders. Refractive indices and film thickness of the self-assembled thin film determined by using the prism coupling method revealed that the self-assembled DNA thin film has anisotropic structure in two-dimensional and the self- assembled DNA-CTMA thin film is isotropic. The functional dye-DNA-CTMA film may be used to fabrication of optical waveguide, and optoelectronic devices based on the strong flurorescence, and tunable optical properties.

Time-resolved degenerate four-wave mixing (DFWM) experiments performed on films of triphenylamino-phenylene vinylene (TPA-PPV) copolymer show the modulus of the nonlinear refractive index to be (2.1#0.4) x10-13 cm2/W at 800 nm. The polymer was synthesized in the Hoerner-type polycondensation reaction. The films were characterized by optical absorption spectra, molecular weight and glass transition temperature measurements. The linear refractive index measurements performed with a prism coupler indicate that the annealed polymer films are isotropic. The films showed waveguiding of light. The DFWM experiments were performed in the forward BOXCARS geometry with simultaneous monitoring of the phase-matched and the non-phase-matched signals. This allowed measuring the nonlinearity of sub-micrometer thick films even in the presence of signals from a thick glass substrate. A cubic power dependence of the diffracted signal vs. pump intensity was observed as expected for the Kerr-type electronic nonlinearity. The signals showed a strong instantaneous response followed by a slow decay with the time constant 9#2 ps. Z-scan measurements showed the presence of two-photon absorption in the polymer.

Colossal Storage Inc. has exclusive license patent rights on new ways of non-contact reading and writing with nondestructive reading of information to a ferroelectric molecule. These methods will be used to develop the world's first 2 D/3 D Area/Volume Holographic mass storage device. U.S. Patents #6,028,835 and #6,046,973 4/00 for an integrated read/write head for ferroelectric optical media.

A diffractive micro-optics element with hybrid functions has been designed to perform Inertial Confinement Fusion (ICF). The functions of a lens, a low efficiency beam sampler, a Color Separation Grating (CSG) and a binary optical element for target uniform illumination has been integrated to the diffractive optical element (DOE). Its phase distribution is continuous on a disk with diameter of 45mm. The focal length of element is 2400mm. Sampling efficiency for 3ω+(0.351um) light at +1 diffraction order is under 0.1% and the space between sampled beam and focal spot is more than 30mm on the target plane. Unwanted harmonic waves of fundamental wave (1ω+) at 1.053 um and second harmonic wave (2ω+) at 0.527 um are diverted out of the high power laser system and the remnant ratio of them at zero order are less than 2%. Meanwhile, the micro-optics element has excellent ability for beam uniform. The side lobe of the 3ω+ focal spot is suppressed very well and the root-mean-square percent error of its top uniformity is less than 1.5%. Although effected by focusing, beam sampling, color separating and beam smoothing, the synthetic efficiency of 3ω+ light is more than 96%. For the functions integrated diffractive micro-optics element, different designing methods have been applied to implement its corresponding aims. The compatibility, fabrication method and influences between the hybrid functions are discussed in detail.

Vanadyl-phthalaocyanine (VOPc) films were prepared on KCI substrate by a molecular beam epitaxy (MBE) method. The SEM image revealed that a VOPc single crystal of 120)mumX120)mum grew on the KCI substrate after annealiing for 360 minutes. Its average film thickness was about 110 nm. The growth of single crystal was assisted by the surface diffusion of VOPc molecules and the difference in chemical potential between single crystals. Therefore, the single crystal grows merging neighboring grains and/or VOPc molecules surrounding. The VIS/UV spectrum of single crystal had the absorption peaks at 700nm and 860nm and also the absorption shoulder at 640nm. The maximum absorption peak is at 860nm. According to Griffiths et al., the phase having peaks at 680nm and 740nm is called Phase I and the phases having a main absorption peaks at 820nm and 830nm are called Phase II and Phase III, respectively. Phases having a main absorption peaks at 780nm and 810nm are called Pseudomorphic layer and epitaxial growth, respectively. As mentioned above, the phase having a main absorption peak at 860nm has not been reported so far. We call it Phase IV. The VOPc film having Phase IV shows a third harmonic (TH) generation. The TH susceptibility is larger by about 10³ times than that of quartz glass. This indicates that Phase IV has high molecular packing density and good nonlinear optical properties. Therefore the single crystal on KCI substrate prepared by MBE is expected to apply to optical switching, modulation and memory (RAM and ROM).

In this article, a time-domain non-linear model is proposed for quantum dynamics of interface traps. This model includes the effects of thermoionic emission, combined with the drift and tunneling currents. The model is simplified for the case of interface traps of the directly bonded Silicon wafers, and linearized. Therefore, an equivalent electrical circuit is obtained being composed of two resistive and capacitive branches. The theory predicts a close spacing between the corresponding zero and pole in the frequency response of the system, being justified by experiment on directly bonded n- type Silicon wafers. The low frequency response to a square- wave is quite in agreement with the experiment. This method enables one to precisely measure the filling up time- constant of the interface traps through the falling electroncs from the conduction band, by measuring the frequency response of the interface.

In this paper, exact analytical forms of the normal surface and eigenpolarizations in anisotropic media are obtained. Both the permitivity and permeability tensors are supposed to be anisotropic, becoming simultaneously diagonal in the principal system of coordinates. The equation of normal surface in various forms and exact relations for eiggenpolarizations are presented and their properties are discussed. Orthogonality relationships between the eigenmodes are also introduced. Sufficient conditions for existence of two, one, or no optical axes are thoroughly established. The analysis is extended for the case of electrically or magnetically optically active materials, and exact form of eiggenpolarizations are derived. It is shown that for the medium with no optical axes, being referred to as pseudo-isotropic medium, under certain conditions there is exactly no reflection. This phenomenon is totally independent of the polarization, angle of incidence, and even wavelength.

Using the rate equations which describing the dynamic processes in Er³⁺ doped pentaphosphate crystals, the upconversion mechanism in this system under 650nm excitation was gotten, and the influence of the concentration of Er³⁺ ions on the dominant populate process of the upper state of the upconversion luminescence was analyzed. The spontaneous radiate processes, multiphonon nonradiative processes, stimulated transitions and the possible energy transfer processes between all states of Er³⁺ ions were included in the rate equations, and the pump power was supposed to be unchanged with time. It came to the result that under weak excitations, the main upconversion mechanism in ErP₅O₁₄ crystal was energy transfer upconversion, and contribution from excited state absorption was small. And some nonresonant energy transfer processes played an important role in building up of the population of the upper state of some upconversion luminescence. Such as nonresonant energy transfer process (3->1, 5->12), the energy mismatch of which is 1585cm^-1;31.1% of the ions of ⁴G_11/2, the upper state of 379nm upconversion luminescence, was populated through this processes. Since changed concentration of Er³⁺ ions would cause changed distance thus changed energy transfer rate between them, and then the contribution of all processes in the system would be different. The result showed in Er_xLa_1-xP₅O₁₄ crystal with different x, the upper states of the upconversion luminescence were populated from different process, with the concentration of ER³⁺ ions increased, the influence of energy transfer upconversion processes (Including some nonresonant energy transfer) became larger.

Using the rate equations describing the dynamic processes of the system, how the strength of the upconversion luminescence change with the Er³⁺ ion concentration and the pump power was analyzed. The spontaneous radiative processes, multiphonon nonradiative processes, absorption of the pump photons and the possible energy transfer processes between all states of Er³⁺ ions were included in the rate equations, and the pump power was supposed to be unchanged with time. It came to the result that when x change from 0.1% to 100% in Er_xLa_1-xP₅O₁₄ crystal, lager x benefit the population of all states higher than ⁴F_9/2 in the whole range of pump power we considered, except for a small range of pump power in which smaller concentration result in larger ion number of some high lying states. It can be interpreted as that the increasing of the concentration of Er³⁺ ions increases both energy transfer processes which populate the upper states of the upconversion luminescence and the cross relaxation processes which depopulate these states. Since the strength of upconversion luminescence is in proportion to the ion numbers of the upper states of the luminescence, the total result is that the upconversion luminescence from ⁴S_3/2 would increase with the concentration of Er³⁺ ions, and the strength of this upconversion luminescence were most strong in ErP₅O₁₄ crystal; for a small range of pump power, the strength of upconversion luminescence from level (²G⁴F²H)_9/2 and ⁴G_11/12 of Er ions in Er_{0.8La(subscript 0.2}P₅O₁₄ crystal was most strong, for all the other range of pump power, this luminescence was also strongest in ErP₅O₁₄ crystal.

Rate equations describing the dynamic processes in Er³⁺ doped pentaphosphate crystals were built up. Using this rate equations the dynamic processes of the building up processes of the populations of the states of Er³⁺ ions in ErP₅O₁₄ crystal was gotten. The spontaneous radiative processes, multiphonon nonradiative processes, absorption of the pump photons and the possible energy transfer processes between all states of Er³⁺ ions were included in the rate equations, and the pump power was supposed to be unchanged with time. Considered that the equation n(t₀+(Delta) t)=n(t₀+dndivided bydt(Delta) t would be held if (Delta) t was small enough, and using the initial condition n₁=1.0, n_i=0(idoes not equal1), the time dependent populations of all states could be gotten from the rate equations. When the pump power was 10³W, population of the ground state decreased rapidly with time and then tended to stable, at the same time, the population of ⁴F_9/2, the state excited directly by the pump light, formed a peak-like structure and then tended to stable. The gradient of the decay side and the rising side of this structure was close, which believed to be the result of the large number of the energy transfer processes between ⁴F_9/2 and other states and the great rate of these processes. Populations of the other excited states lower than ⁴F_9/2 were all increase at first and then decrease with time while excited states higher than ⁴F_9/2 were all increase with time and then tended to be stable. The system came to be stable at about 140 microsecond(s) .

In the paper, a thin tensile GaAs interlayer was used to get regular arrangement of InAs quantum dots (QDs) on InP substrate by LP-MOCVD. Photoluminescence (PL) spectrum, atomic force microscopy (AFM) image and Raman spectrum have been investigated. The five band k(DOT)p formalism in the PL spectrum and frequency shift in Raman spectrum have been performed. The theoretical calculations coincide with our experiment results well. The density of InAs quantum dots at 4 ML InAs is the maximum (1.6X10¹⁰cm^MIN2).

In this paper, we deposited high quality ZnO film by plasma-assisted Metal-organic Chemical Vapor Deposition (MOCVD). A dominant peak at 34.6 degree due to (002) ZnO was observed indicating strongly C-oriented. The full-width at half-maximum (FWHM) of the (-rocking curve was 0.56 degree showing relatively small mosaicity. Transmission spectrum showed that the bandgap of ZnO film was about 3.31 eV at room temperature. Photoluminescence (PL) measurement was performed at both room temperature. Ultraviolet (UV) emission at 3.30 eV was found with high intensity at room temperature while the deep level transition was weakly observed at 2.513 eV. The ratio of the intensity of UV emission to that of deep level emission was as high as 193, which implied high quality of ZnO film. The resistivity of ZnO film was increased after annealing under Oxygen while its optical quality decreased.

All-optical control of the noncentrosymmetry of azodye-doped polymer films was demonstrated by nonresonant dual-frequency coherent excitation. Three kinds of noncentrosymmetries of the polymer films were optically tailored using appropriate combinations of the writing beam polarizations. The characteristic kinetics of the photoinduced molecular polar orientation and the tensor analysis were performed by monitoring SHG of the films. The SHG conversion efficiency of a 105)mum thick film was estimated to be about 2%. It was observed that when polarizations of the writing beams were changed from the linear polarization to the circular polarization the saturated SHG signals were enhanced even at the same readout condition. A relaxation retardation effect of the photoinduced (chi) ⁽²) was also observed in the thick films. The quadratic dependence of SHG on film thickness showed that a (chi) ⁽²)grating satisfying the phase-matching condition for SHG was optically induced in the polymer films, indicating this nonresonant all-optical poling can be used to tailor the symmetry of bulk samples.

The process of electroluminescence (EL) decay of devices made by a trivalent europium (Eu) complex, Eu(DBM)₃(phen)(DBM=dibenzoylmethane, phen=phenanthroline), dispersed in poly(N-vinycarbazole) (PVK), has been studied. The decay process exhibits the characteristics of the time constant being independent of the intensity of pulsed drive voltage and the EL intensity having nearly single exponential dependence on the decay time. The decay process is considered as the monomolecular recombination process. By analyzing the process, we believe that the charged carrier concentrations (involving both holes and electrons) at initial state (the decay time t=o) do not influence the time constant, indicating that injected holes and electrons within PVK film are of unbalance seriously. From this point of view, we discussed an efficient device based on Eu(DBM)₃ (phen) dispersed in polymer structure.

The modern trend in focal plane arrays (FPAs) implementation is to include an increasing amount of analog signal processing in micro technology circuitry embedded in the FPA construction. This technology includes such function as time-delayed integration (TDI). While such integration makes the FPA and its associated signal processing more compact and faster, it introduces new complications into the testing of the FPA, since the detector outputs, by themselves, are no longer directly accessible. The CdHgTe FPAs detectors with on-chip TDI have been successfully incorporated into infrared imagers. These impose requirements on the instrumentation to establish the modulation transfer function (MTF) of the integrated FPAs. This paper details a method for measuring the MTF for such arrays within 3-5μ+m and 8-14μ+m spectral band. A description of a test facility for testing and evaluating MTF of FPA is given. We use a knife-edge target to measure MTF. The Pentium III computer system takes the charge of controlling and calculating. Some other methods of MTF measurement will be mentioned.

Multiple quantum wells (MQW) microdisk lasers are fabricated by using the methods of photolithography-etching techniques. By the CCD watching-control and micron-area detecting systems, The 5µm-diameter microdisk lasers was optically pumped by Ar+ pulse laser at room temperature, with the 1:50 pump duty cycle. We obtained the single-mode lasing at 1.543&#61549m wavelength, with threshold pump power about 200µw.

The vertical tunneling transport of selectively and resonantly photogenerated carriers in a composite quantum-well system, consisting of dual multiple-quantum-wells (MQWs) with different heterostructures, i.e., GaAs/AlGaAs (MQW1) and strained InGaAs/AlGaAs (MQW2), is experimentally investigated at 15 K as a function of electric field by photocurrent (PC) response and photoluminescence (PL) measurements. In PC spectra of this novel structure, distinct pseudo-negative peaks are observed at the exciton resonance wavelengths of the front MQW1. Origins of the pseudo-negative PC peaks are explained by shadowing effects on the number of photons absorbed in the MQW1 layer and by assuming the dominance of electron transport. In the PC spectra, however, the excitonic peaks of the rear MQW2 shift to the lower energy side with increasing the electric field, while no significant shifts are observed for the negative PC peaks of MQW1. In addition, the applied reverse bias dependence of the PL intensities indicates faster decreases for the MQW2 layer, while the strong PL intensity persists at much higher fields for the MQW1 layer. These results clearly indicate that selective carrier injection into the MQW layers causes a non-uniform distribution of the applied electric field, which is useful to realize the charge-induced optical switching between the two MQW layers.

One of the most important technological challenges in the manufacture of high power lasers is to determine device quality and reliability without damaging the device itself. The low-frequency electrical noise has shown potential as a sensitive non-destructive indicator of device quality and reliability. In this paper, the noise levels in semiconductor lasers (LDs) operating in both unconducting state (Svl) and conducting state (Sv2) are measured. From our investigation, the device reliability is associated with not only Sv1 but also Sv2, if one of them is higher, the device is usually reliable. When the noise is used to estimate device reliability, both Sv1 and Sv2 should be measured and considered.

Spectral response is an important parameter of photocathodes. By analyzing measured spectral response curves, much information about the photocathodes can be obtained which is useful to investigation of photocathodes. The principle measuring the spectral response of photocathodes is expounded in this paper. The on-line measurement system was developed, which can measure the spectral response of optoelectronic devices within range of 400nm~1800nm. It can also measure the reflectance of monochromatic light, the monochromatic photocurrent, and integral sensitivity of photocathodes. The measurement system was used to on-line measure spectral response of multi-alkali photocathodes(Na2KSb:Cs) when they are being prepared. Combining measurement of reflectance of monochromatic light, by which the thickness of photocathodes can be timely obtained, the optimum thickness of photocathode is looked for. The measurement system also used in the investigation of GaAs:Cs-O NEA photocathodes. Surface escape probability, electron diffusion length and back-interface recombination velocity are the factors that influence the quantum yield of NEA photocathode. It is difficult to directly measure these parameters. But they can be obtained by simulation of measured spectral response. The reflective GaAs samples were activated and evaluated. The results were given and analyzed.

Waveform sampling of the positive ECL signals generated from microwave frequency divider by using a delay-line-free electro-optic sampling system with a voltage-controlled phase-tuning circuit is primarily reported. The distorted waveform of the ECL signal frequency-prescaled from microwave oscillator operated at high output level is sampled and compared by using the proposed technique and the conventional sampling oscilloscope. The divisor of the frequency prescalar is found to vary from 2 to 5 at input power of less than 114dBm.

We study the results of picosecond optical pulse train amplified by a traveling-wave semiconductor optical amplifier (TWSOA). The distortion of multi-Gigabit optical carriers or pulses generated from gain-switched optical transmitters due to the nonlinear phenomenon inherent in the TWSOA is discussed. The trend in saturation of output power and gain of the optical pulses is observed. The effect of injection current and operating temperatures on the performance of TWSOA in amplification of picosecond negatively chirped optical pulses from gain-switched laser diode with gigabit repetition rate are characterized. Optimal conditions of injection current and operating temperature for the TWSOA are determined, and those for the gain-switched optical transmitter at below threshold and lower than room temperature are obtained. The shortest pulse generated from gain-switched optical transmitter is found to be distorted from 21 ps to 30 ps after amplifying by TWSOA.

Lasers based on InGaAs/(Ga,Al)As stacked QDs layers are fabricated. The performance of the quantum dots laser is dependent on the detailed design of the active region. The threshold current density is greatly decreased by the use of multiple-layer quantum dots, coupled dots layers, or barriers with wide band gap. An average threshold current density of about 20A/cm2 is achieved for the laser with the width of 15micron.

In this paper we report a 980 nm InGaAs/GaAs MQW semiconductor laser array. The epilayer structures are grown by MBE. We have fabricated broad areas lasers with a cavity length of 1000micron and a stripe width of 6micron and a stripe spacing of 100micron. The measurements are performed in quasi-continuous wave mode (QCW). The highest QCW output power of 12W for laser array with coated facets is achieved. The threshold current density is 400 A/cm2 at 15degree. The slope efficiency is 0.74W/A. The lasing spectrum is peaked at 979.4 nm with a FWHM of 3nm.

The multiple layers quantum dots structure was grown by MBE technology. The temperature dependence of the modal gain of quantum dots was investigated by using the single pass amplified spontaneous emission method. The incorporation of extra layers of quantum dots didn't lead to an increase of the modal loss, inferring that the free carrier absorption in the doped cladding layers might dominate the loss mechanism. The peak modal gain exhibited an increase with temperature in the region of 140K to 200K, presumably due to the non-equilibrium distribution of carriers among the quantum dots.

Nd:YVO₄ crystal was successfully grown by the Czochralski method. The crystal growth process was described in detail: The transmittance and emission spectra of Nd:YVO₄ crystal have been measured. The wavlength of the main absorption peak is centered at 808.97nm, and that of the emission peak is centered at 1064nm. The fluoresence lifetime of (formula available in paper).

Doping Eu₂o₃ and CeO₂ in LiNbO₃, Ce:Eu:LiNbO₃ crystal was successfully grown by the Czochralski method. The lattice constants of Ce:Eu:LiNbO₃ were calculated. For the reason of volume compensation effect, that lattice constants of Ce:Eu:LiNbO₃ were smaller than that of Ce:LiNbO₃ and Eu:LiNbO₃. It was found in the absorption spectra that the absorption band of Ce:Eu:LiNbO₃ has the most red shift, and this phenomenon was explained. The response time of 32s, refractive efficiency of 75% and exponential gain coefficient of 22cm(superscript -1 of Ce:Eu:LiNbO₃ was obtained by the holographic method. In the end, using Ce:Eu:LiNbO₃ as storage medium, the holographic associative storage was realized and the clear and integrated retrieval graph was obtained.

Optical limiting property of two types of charge transfer salt [M(DMID)₂][C]_x and [M(DMIT)₂][C]_x (M = Ni, Cu) (C=TMA, TBA) is studied. The comparison of these two series complexes demonstrates that the optical limiting effect of the Ni-based complexes is better than that of the Cu-based complexes, both of them are a little less than that of C₆₀. The nonlinear absorption coefficient that determined by optical limiting technique for Ni-based complexes is about one order of magnitude higher than that of Cu-based complexes. On the other hand, partial charge transfer may enhance the optical limiting effect in the Cu-based complexes, but it doesn't occur in the Ni-based complexes. All may be attributed to the typical column structure that caused by plan configuration.

Polarization-insensitive semiconductor optical amplifiers (SOA's) with tensile-strained multi-quantum-wells as actice regions are designed and fabricated. The 6x6 Luttinger-Kohn model and Bir-Pikus Hamiltonian are employed to calculate the valence subband structures of strained quantum wells, and then a Lorentzian line-shape function is combined to calculate the material gain spectra for TE and TM modes. The device structure for polarization insensitive SOA is designed based on the materialde gain spectra of TE and TM modes and the gain factors for multilayer slab waveguide. Based on the designed structure parameters, we grow the SOA wafer by MOCVD and get nearly magnitude of output power for TE and TM modes from the broad-area semiconductor lasers fabricated from the wafer.

The pure congruent LiNbO₃, Er:LiNbO₃ and Zn,Er- codoped Li-rich LiNbO₃ crystals were grown by Czochralski method. In order to analyze their structure, the X-ray diffraction method, ultraviolet-visible absorption spectra and infrared absorption spectra of the crystals were investigated. The photo damage resistance ability of the crystals was measured. The Zn,Er-codoped Li-rich lithium niobate crystals showed a decrease in lattice constant values, a shift in absorption edge of ultraviolet-visible absorption spectra towards shorter wavelength, and increase in OH_- absorption peak of infrared absorption spectra towards longer wavelength, and three orders of magnitude increase in phtorefractive damage resistance compared to congruent LiNbO₃ crystal.

Nondoped, Fe₂O₃ and Eu₂O₃-codoped near stoichiometric LiNbO₃(Eu:Fe:LiNbO₃) single crystals were grown by the top-seeded solution method. The solution with [Li]/[Nb] ratio of 1 contained K₂O component of 10.6mol%(7.0wt%). The ultraviolet-visible absorption spectra, infrared absorption spectra of the crystals were measured in order to analyze their structure. The photorefractive properties of stoichiometric LiNbO₃ crystals were investigated and compared with congruent LiNbO₃ crystal. Two-wave-coupling experiments shown that doped stoichiometric LiNbO₃ crystals exhibited much larger photorefractive gain and faster response speed than congruent ones.

Ca₄YO(BO₃)₃ crystal doped with Nd³⁺ has been grown by the Czochralski method under air atmosphere. The growth conditions were studied in the paper. X-ray powder diffractogram, the absorption spectra and infrared spectra have been measured. The effects of ions in the crystal on the absorption peak of OH^- have been also discussed. The second harmonic generation (SHG) and self- frequency-doubling (SFD) experiments were carried out on the sample with the dimension of 4x4x8mm³.

La:Zn:KLN single crystal was grown by the Czochralski method with the dimensions of 10x10x35mm. The crystal was polarized. The crystal structure was determined by X-ray diffraction. The Curie point was determined by the difference thermal analysis. The infrared spectra was obtained. The doubling frequency light of 434nm was obtained in the La:Zn:KLN with the base light of 868nm.

CeO₂ and MnCO₃ codoped Potassium Lithium Niobate single crystals were grown by the Czochralski method. It was shown that Ce ions would be precedently substituted for the site of K by the absorption spectra and X-ray diffraction patterns. Otherwise Mn would be substitute for the site of Nb. The response time, exponential gain coefficient and effective carries density was measured by the two beam coupling. The effect of Oxide and reduced treatment on these parameters was researched.

Ce:Eu:SBN single crystal was grown by the Czochralski method. The crystal was polarized. The exponential gain coefficient, response time and diffraction efficiency were measured by the two beam coupling. The phase conjugation reflectivity was also measured by four beam mixed path. The results showed that the photorefractive effect of Ce:Eu:SBN was superior to that of SBN and Ce:SBN.

Utilizing large dispersion of a chirped fiber Bragg rating (CFBG), a wavelength tunable mode-locked fiber ring laser was obtained in the band width of the CFBG. Compared with the structure included dispersion compensating fiber, the supermode noise and enviment influence were suppressed. The 2.5GHz pulses were generated.

Research on the one-mirror-inclined three-mirror-cavity (OMITMC) photodetectors in our laboratory is reported. In the structure of the photodetectors, it is the inclined- mirror that makes the filtering cavity and the absorption cavity decoupled, thus narrow spectral response linewidth, high-speed and high quantum efficiency can be achieved simultaneously. On the basis of the theoretical analysis, we do realize the vertical taper structure, the key part in the whole integrated device, by dynamic etch mask technique. Moreover, the first integrated device of this type was fabricated. A spectral response linewidth less than 6nm and a quantum efficiency of 52.6% have been achieved experimentally.

Many phase retrieval algorithms are used for the designing process of diffractive optical element (DOE). To design a DOE, it is almost the occasions to recovery phase distribution on the micro-optics element when the amplitude distribution of inputting plane and outputting plane has been known. Generally, there are two kinds of strategies to resolve phase retrieval problems, namely iterative method and try-and error method. There are a lot of famous algorithms have been successful used in this field, such as Gerchberg and Saxton (GS), ST, Input-Output, Yang and Gu (YG) etc. In this paper, a novel algorithm is brought forward. The phase on DOE is considered as the superposition of a serial of sinusoidal curves. Randomly, a concrete sinusoidal phase disturbance with definite frequency and amplitude is selected. Correspondent disturbance complex amplitude distribution on image plane can be considered as transformation result of the disturbance phase by the optical system. Then, new complex amplitude on image plane can be calculated as the convolution of its original one and the disturbance one. By Simulated Annealing algorithm, the optimal frequency and amplitude for the sinusoidal phase disturbance are searched. Gradually, when enough sinusoidal phase disturbances are searched, the phase of DOE will approximate to its global optimum solution. At last, for the optimum phase solution, phase smoothing method is used to relieve jump discontinuity.

In this paper ,high quality AlGaAs/GaAs single quantum well(SQM) structure is grown on (100) GaAs substrate by molecular beam epitaxy (MBE) system. Optical and structural characteristic of the film was studied by low temperature (10K) photoluminescence (PL) and X-ray double crystal diffraction method. Using X-ray kinematical theory, we calculated the structure parameters of each samples, the reason for the appearance of the interfering fringes and splitting peaks in double crystal rocking curve were analyse theoretically. The deep levels which affect character of the material and laser are also discussed. The experimental results show that measuring methods of the photoluminescence and X-ray double crystal diffraction are very important for testing the quality of quantum wells and improving the MBE technology.

Neglecting the effect of generation-recombination (G-R) current, tunneling current, and surface leakage current, a loophole p-n junction current and R₀A expression is developed in this paper. The R₀A characteristic varying with temperature and long-wavelength is carried out for 77- 150K temperature range. The curve indicates that the detectors are applicable at 8-10.4micrometers wavelength range for 120K and ever low temperature, but only when the temperature is below 100K, 10~14micrometers wavelength detectors can be used. These results are agree well with that of planar p-n junction's theoretical upper limit. Finally, according with the dependence of G-R current and diffusion current on temperature, the characteristic and function are set up between temperature and composition which equate the generation-recombination current to diffusion current.

The second-order nonlinear optical (NLO) properties of three new organic stilbazolium salts (denoted by Dye1, Dye2 and Dye3) were studied by hyper-Rayleigh scattering (HRS) technique. Dye2 and Dye3 are dichromophoric systems of Dye1 with combined bridges of different lengths. Because all the samples are ionic species, the classical technique electric- field-induced second-harmonic generation (EFISHG) can not be used to measure their first hyperpolarizabilities (beta) . Further studies showed that the measured (beta) values were greatly enhanced due to the multi-photon fluorescence (MPF) emissions at 532nm, and more accurate (beta) could be estimated after grossly cutting off the MPF from their spectra. It shows that the stilbazolium salts are good candidates with very large first hyperpolarizabilities (in the range of 10^-27esu) for optoelectronic applications. The results revealed the dependence of (beta) on the molecular structures such as number of chromophore, (pi) -conjugation length and molecular conformation in the solution of dimethylformamide. The two level mode was used to predict the intrinsic molecular hyperpolarizabilities of these samples.

In this paper, through the analysis and in consideration of the facts which influence on the ultimate output power of semiconductor laser. we report a novel 940nm semiconductor laser array structure with nonabsorbing facets to avoid the COMD on facets. The 940nm laser wafers are grown by MBE. The lasers were cleaved into cm bars. We have made a new design variant of laser array with nonabsorbing facets and coated high-and low-reflectivity coating (approx.95% and 5%). The emission wavelength of the laser arrays is 939nm. Continuous wave (CW) output power of 15 W has been achieved.

In this paper, we report on structure design of high-power InGaAs/AlGaAs/GaAs fold cavity surface-emitting laser (FCSEL) with 45 degree(s) intracavity micro-mirror. The epitaxial material for these devices was grown by molecular beam epitaxy (MBE) technique. Optical and structural characteristic of the film was studied by photoluminescence (PL), X-ray double crystal diffraction and electrochemical C-V profiling method. The radition wave length 0.921um of sample is obtained at low temperature (10K) PL spectrum. The results of X-ray double crystal rocking curve and low temperature (10K) PL experimental show the structure design of folded cavity surface-emitting lasers is realized By MBE.

This article first describes the background of the research and manufacture of evaluation system of Negative Electron Affinity photocathode. This article designs a set of super high vacuum system for activating NEA photocathode on the base of activation theory, the process of design and debugging is given. The system is composed of three parts: super high vacuum system for GaAs material activation, multi-meter testing system, surface analysis system. The system is used for on-line evaluation of activating of NEA photocathode. The technical parameters and structure of the evaluation system of NEA photocathode are given in the paper. The system is finished and experiments are made. At last the picture of the system is given.

In this paper, on the base of explaining the importance of spectral response, the way to derive characteristic parameters of NEA photocathode from its spectral response is introduced. Then, an automatic spectral response recording system is described. The system is used to take spectral response curves during the activation procedure. For the first time, on-line measured spectral response curves of GaAs:Cs-O NEA photocathodes are presented. These curves indicate the typical variation in spectral response caused by the deposition of cesium and oxygen. By the way of comparing and analyzing these curves, many important parameters of photocathodes are obtained, and the reasons that cause the bad behavior of NEA photocathodes are discussed.

On-line spectral response curves of GaAs:Cs-O NEA photo- cathode of reflection model is first presented and the relation between spectral response curves and the thickness of Cs-O layer is discussed. When Cs and O is deposited on the surface of cleaning GaAs wafer, photo-cathode's spectral response rises sharply and long-wavelength threshold tends to a fixed value at the beginning of the activation. But, as Cs and O are deposited continually, spectral response rises slowly and the long-wavelength threshold tends to be shortened. When a fine thickness of Cs-O layer is reached, the optimum spectral response is obtained. As a quantity Cs-O is further increased, both the spectral response and the long-wavelength threshold decrease. The thickness of GaAs photo-cathode surface layer that consists of Cs-O layer and GaAs-O layer is researched by take-off angle XPS technology. Thickness of Cs-O layer is approximately equal to 0.7 nm, and the GaAs-O layer is approximately 0.2nm. Our experiments show when the thickness of Cs-O layer is approximately equal to 0.7nm, and the GaAs-O layer is approximately 0.2mm. Our experiments show when the thickness of Cs-O layer is 0.7nm or so and the GaAs-O layer tend to be disappeared, NEA photo-cathode with the optimum spectral response is achieved which can be used widely in low-light level imaging detectors.

In this paper, diamond film is deposited at low substrate temperature by electron-assisted chemical vapor deposition (EACVD). The quality of diamond film is analyzed by the scanning electron microscope (SEM), Raman spectrum and x-ray diffraction (XRD). The results show that the high quality film of (111) orientation is deposited at low temperature of about 500 degree(s)C by the EACVD technique. Meanwhile, the mechanism of the deposition at low temperature is also discussed.

The polarization of vertical-cavity surface-emitting laser (VCSEL) can be controlled by electro-optic birefringence. We calculated the birefringence resulted from external electric field which was imposed on the top DBR of VCSEL by assuming that the two polarization modes were in the same place of the gain spectra in the absence of electric field beginning. By modifying SFM, the affection of the electric field strength on the polarization switching currents between the two polarization modes had been shown.

The Si-rich a-SiN_x films are synthesized by pulsed laser ablation of silicon target under NH₃ atmosphere. By using laser-induced crystallization technique, the fabrication of nc-Si embedded in the SiN_x is also realized. The crystallinity and microstructure of the films after laser annealing are characterized by scanning electron microscopy and micro-Raman spectroscopy. Additionally, in order to investigate the role of the SiN_x on protecting the nc-Si from the oxidation in the air, the energy diffraction X-ray spectrum is also carried out. By photoluminescence (PL) spectrum measurement, the PL peak blue shifting is observed at room temperature. The results suggest that nc-Si embedded in the silicon nitride could be effectively passivated and stable PL of nasnosilicon grains could be obtained.

Silicon nanocrystals have been synthesized using pulsed laser ablation in argon background gas. The morphology structure and the size distribution of the silicon nanocrystals depending on the background gas pressure (0.1 Pa-100 Pa) have been studied. Experiment results show that the morphology of the silicon nanograins transits from amorphous-like continuous thin film to dispersed nanocrystals with the decreasing of argon pressure. The size of the silicon nanograins increases with the increase of argon pressure (less than 100 Pa). Under higher pressure the size of the silicon nanograins does not increase with the increase of the background pressure monotonously, it comes to a maximum at a critical gas pressure, then begins to decrease when increasing the gas pressure.

In this paper we present the results of theoretical analysis and numerical analogue on the transient characteristics of a semiconductor system responding to the incident signal field, especially for the situations in which the system is with lasing effect and display a novel increasing absorption bistable state. The results appear some different features with that of other known bistable device and lasers. These results may be available to a class of excitonic bistable lasing systems.

We propose here a device for measuring the ellipticity of light. Its core element is a polarization diffraction grating. As far as we know, no other similar device has been developed so far. To record the grating holographically we used a Mordant Pure Yellow azodye in a matrix of gelatin. This media acquires relatively high values of birefringence (over (Delta) n = 0.02) which can be stable for more than a year and no surface relief appears during the recording Thanks to these advantages we succeeded to record polarization diffraction gratings that can be used as circular analyzers. Diffraction efficiency of 67% is achieved at 633nm. Based on that polarization grating, a novel type of a compact ellipsometric device working with white light was built. The different wavelengths are spatially separated and measured by means of a CCD line. The device has no moving parts and permits measuring of the ellipticity at different wavelengths simultaneously in real time at a high speed (only electronics limited). Initial experiments with the device were done.