This PDF file contains the front matter associated with SPIE Proceedings Volume 7135, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.

Hybrid photonic integration with passive assembly techniques allows compact optical modules to be realised with high optical performance and low packaging cost. Recent advances in integrating semiconductor optical amplifiers into practical all-optical signal processing modules is described, with applications from optical memory to sophisticated burst-mode optical regenerators.

This paper reports recent advances on arrayed waveguide grating (AWG) multi/demultiplexers based on silica-based planar lightwave circuits (PLC). After briefly summarizing the fabrication and properties of PLCs, this work describes a Mach-Zehnder interferometer (MZI)-synchronized AWG with reagrd to reduced loss, and athermalization. The paper then reports our recent demonstration of the integration of a PLC-based wavelength selective switch (WSS) and an integrated single-chip VMUX/DEMUX.

We have developed the uncooled electroabsorption modulator integrated distributed feedback (EA/DFB) lasers for small-footprint and low-power-consumption transceiver modulus. In this study, we used the temperature-tolerant InGaAlAs materials in EA modulator. We investigated the 10.7-Gbps, 40-km transmission performances over wide temperature range. The dynamic extinction ratio was 9.9 dB and 13.3 dB at the 10ºC and 85ºC. The modulated output power was more than +3.7 dBm even at 85ºC. The long-term reliability was also investigated under APC condition at ambient temperature of 85ºC with starting current of 120 mA. There was no significant degradation of the operation current up to 5000 hours. Uncooled 1300-nm range 25-Gbps and 43-Gbps EA/DFB lasers were also investigated. These devices will provide cost-effective 100-Gbps and 40-Gbps transceiver for next-generation high speed network system. A wide temperature ranged 12-km transmission with over 9.6-dB dynamic extinction ratio was demonstrated under 25-Gbps modulation. A 43-Gbps 10-km transmission was also demonstrated. The laser achieved clearly opened eye diagrams with dynamic extinction ratio of over 7-dB from 25ºC to 85ºC.

Directional emission semiconductor microcavity lasers integrated with semiconductor planar technique are potential light sources for photonic integrated circuits. In this article, we investigate mode characteristics for equilateral triangle and square microcavities for realizing directional emission microcavity lasers. The analytical mode field distributions and mode wavelengths are presented for two-dimensional (2D) triangle and square resonators, and directional emission are simulated by finite-difference time-domain (FDTD) technique. The numerical results of mode Q-factors and output coupling efficiencies for the triangle and square resonators show that high efficiency directional emission microcavity lasers can be realized by directly connected an output waveguide to the resonators, because the mode field patterns are standing distributions in the triangle and square resonator. Laser output spectra of fabricated InGaAsP/InP triangle lasers are compared with the analytical results.

An integrated, compact and upgradeable bidirectional multiplexer/demultiplexer and Add-drop multiplexing based on array of ring resonators is proposed. The proposed structure is realized using basic elements in optical integrated circuit domain. We show that using the proposed block wavelength separation in dense wavelength division multiplexing standard is possible. Also, the introduced basic block can be used to realize other elements in all-optical networks.

The size dependence of photoluminescence (PL) from nanostructure semiconductors is examined. Considering the dependence of PL on both the silicon nanoparticles (Si NPs) sizes and their dispersion, we incorporated quantum confinement effects along with the effects of localized surface states to obtain an analytical expression for the PL spectra of silicon nanostructures. In order to obtain an insight into the effects of various parameters influencing the PL spectral profile in silicon nanostructures, we computed the PL spectra using relevant numbers in the expression. The computer-simulated results show (i) a marked deviation of PL spectrum from the normal distribution at higher energies due to the increase in oscillator strength with the decreasing mean Si NP size, (ii) The peak position redshifts and the peak intensity reduces with an increase in the standard deviation, and (iii) the luminescence peak blueshifts as the mean Si NP size decreases. To test our model, the Si NPs embedded in silicon nitride films were prepared by helicon wave plasma-enhanced chemical vapor deposition (HWP-CVD) technique using the H₂ diluted SiH₄ and N₂ as reactant gas sources. The simulated PL spectra fit the experimental one rather nicely. And our results can explain the reported experimental observations on the luminescence from Si NPs.

The optical gain of quantum-dot (QD) semiconductor optical amplifier (SOA) is usually seriously dependent on polarization, we propose QD coupled to tensile-strained quantum-well (QW) structure to obtain polarization insensitive QD SOA. A polarization-dependent coupled carrier rate equation model and multi-section SOA model are used to study the performance of QD-coupled QW SOA. Gain dependence on polarization is studied, TE gain contribution by QWs and QDs is compared, and carrier distribution competition among QWs and QDs is analyzed. It is shown that polarization insensitive gain can be realized in a relatively wide range of wavelength if QD-coupled tensile-strained QW SOA is properly designed.

The improvements in efficiency and reliability are essential to realize high performance light emitting diodes (LEDs). Uniform current spreading is very important to enhance both efficiency and reliability simultaneously. 3-dimensional circuit modeling and analysis method was developed in order to figure out influences of current crowding on performances. The method was applied to the top-surface emitting-type LEDs of 320 320 μm² size. It was found that the current crowding was closely related to the improvements in series resistance, saturation of light output power, leakage current with operational time, and endurance of electrostatic discharge (ESD). Defects due to high ESD stress were observed at current crowding area. In order to suppress the peak electric field and enhance the ESD voltage, the floating metal was inserted near the n-electrode. About 4 times larger ESD voltages were experimentally measured at LEDs with floating metal structure compared to without one. A LED with the lozenge shape is fabricated to enhance light extraction efficiency over conventional design, i.e., rectangular parallel piped chip. A lozenge shaped LED has an additional advantage of easy chip making since it has natural crystallographic cleavage planes. About 11% larger light extraction efficiency was experimentally obtained in the lozenge shaped LEDs than conventional rectangular chips.

This work investigates the reactive ions etching (RIE) physical properties of n-type ZnO using H₂/CH₄ and H₂/CH₄/Ar mixtures by varying the gas flow ratio, the radio-frequency (rf) plasma power and the chamber pressure. Atomic force microscopy (AFM) results and surface topographies are discussed. Although the etching rate of the n-ZnO at an H₂/CH₄ flow rate of 100/0 sccm, a work pressure of 100 mTorr and an rf power of 300 W is lower than under any other conditions, the rms roughness of 43.78 nm is the highest, and supports the application of roughened transparent contact layer (TCL) in light-emitting diodes (LEDs). The dynamics associated with the high etching rate were highly efficient at an H₂/CH₄/Ar flow rate of 38/5/57 sccm, a work pressure of 150 mTorr and an rf power of 300 W. In addition, the ZnO with thermal annealing were studied. The slower etching rate of annealed n-ZnO is observed due to an increase the crystal quality of the ZnO films after thermal annealing which consists with the x-ray diffraction (XRD) results.

LEDs (light emitting diodes) can be applied in both illumination and communication. A system of maritime wireless communication with ships based on LED beacons is proposed in this paper. The communication space model and optical transmission model were set up, visible wireless communication manner was analyzed. An anti-fading method combining space and time diversity is adopted due to quick signal attenuation and large noise from nature light interference. After filtering and judgment, the received diversity signals are separated to do bit comparison using Hamming Perception Network. Through analysis and simulation, compared to ordinary space diversity or time diversity way, this kind of anti-fading method can increase reliable communication distance greatly, reduce equipment cost and improve bandwidth utilization rate.

Nowadays, GaN-based multi-layer materials is developing fast, and it is important to know their interface and optical properties for devices design and fabrication. In this letter, the transmission spectra are analyzed, and the dependence of the transmission spectra on parameters of the samples is discussed. Sequentially, we obtain the transmission spectra of a series of GaN-based samples. Simulation of the transmission spectra is done and useful information is extracted. For one of our samples, the refractive index varies a little between 2.518 and 2.305 with the wavelength from 400 to 800nm, while the extinction coefficient is 6x-10^-9.5exp(2700/λ), and the thickness is 2860nm. Finally, we get the dispersion relationship of the GaN and AlGaN films, and it is compared with the results of some other research groups.

Recently, high-Al-content AlGaN alloy systems have attracted increasing attention, and it is urgent and important to achieve excellent Ohmic contacts with low specific contact resistivity, good thermally stability, clear borderline and smooth surface morphology of this alloy systems to optimize the performance of photoelectric devices. In the experiment, we found that surface disordered layer and oxides including native oxide could be removed by boiling KOH solution. The surface status of both samples was evaluated with scanning electron microscope (SEM) and X-ray photoelectron spectra (XPS). For comparison, then A Ti/Al/Ti/Au multilayer was deposited on the samples with and without wet chemical etching to observe their electric properties. After annealing, I-Vcharacteristics via Keyley236 electric analyzer was measured. Ohmic contacts with the contact specific resistivity of 6.55×10^-4Ωcm² were obtained between treated samples and the multi-metals. However, nonlinear I-V curves indicated that the contact on the untreated sample was still the Schottky contact.

Growth of AlN single crystals is achieved by physical vapor transport (PVT) in the reverse cone tungsten crucible, which is induction-heated, for obtaining proper sublimation rate and ensuring effective heat and mass transport. In the experiment, there is a little hole at the center of crucible lid where the temperature is lower than the periphery, and there is a tungsten cover on the lid. A self-seeded AlN single crystal is grown due to the anisotropic growth property of AlN crystals and limitation of the hole. During the following growth, the crystal as a seed becomes a large size and high quality single crystal. By modified PVT, separate AlN single crystals with diameters of larger than 2mm on the crucible lid have been obtained successfully for the first time.

We could have the 30-year anniversary since a VCSEL was invented by Kenichi Iga. We have seen various applications including datacom, sensors, optical interconnects, spectroscopy, optical storages, printers, laser displays, laser radar, atomic clock, optical signal processing and so on. A lot of unique features have been shown, low power consumption, a wafer level testing and so on. In this paper, the brief history and our recent research activities on VCSEL photonics will be reviewed. We present the wavelength engineering of VCSEL arrays for use in high speed short-reach systems, which includes the wavelength integration and wavelength control. The joint research project on ultra-parallel optical links based on VCSEL technologies will be introduced for high speed LANs of 100Gbps or higher. The small footprint of VCSELs allows us to form a densely packed VCSEL array both in space and in wavelength. The wavelength engineering of VCSELs may open up ultra-high capacity networking. Highly controlled multi-wavelength VCSEL array and novel multi-wavelength combiners are developed toward Tera-bit/s-class ultrahigh capacity parallel optical links. In addition, the MEMS-based VCSEL technology enables widely tunable operations. We demonstrated an "athermal VCSEL" with avoiding temperature controllers for uncooled WDM applications. In addition, new functions on VCSELs for optical signal processing are addressed. We present an optical nonlinear phase shifter based on a VCSEL saturable absorber. Also, highly reflective periodic mirrors commonly used in VCSELs enables us to manipulate the speed of light. This new scheme provides us ultra-compact intensity modulators, optical switches and so on for VCSEL-based photonic integration. Also, this paper explores plasmonic VCSELs.

High quality zinc-blende B_xGa_1-xAs, B_xAl_1-xAs, B_xGa_1-x-yIn_yAs epilayers and relevant MQW structures containing 10- period BGaAs(10nm)/GaAs(50nm) and BGaInAs(10nm)/GaAs(50nm) have been successfully grown on exactly-oriented (001)GaAs substrates by low-pressure metalorganic chemical vapor deposition (LP-MOCVD). Triethylboron, trimethylgallium, trimethylaluminium, trimethylindium and arsine were used as the precursors. Boron incorporation behaviors have been studied as a function of growth temperature and gas-phase triethylboron mole fraction. In this study, the maximum boron composition x of 5.8% and 1.3% was achieved at the same growth temperature of 580°C for bulk B_xGa_1-xAs and B_xAl_1-xAs, respectively. 11K photoluminescence (PL) peak wavelength of lattice-matched B_xGa_1-x-yIn_yAs epilayer with boron composition of about 4% reached 1.24μm.

A novel multi-mode model suitable for semiconductor ring lasers with ultra short optical pulse injection including all nonlinear coupling components is established and used to explore multilongitudinal-mode dynamics. Faster switching off time is predicated.

We report on the development of an inexpensive, portable lab-on-a-chip flow cytometer system in which microfluidics, photonics, and acoustics are integrated together to work synergistically. The system relies on fluid-filled twodimensional on-chip photonic components such as lenses, apertures, and slab waveguides to allow for illumination laser beam shaping, light scattering and fluorescence signal detection. Both scattered and fluorescent lights are detected by photodetectors after being collected and guided by the on-chip optics components (e.g. lenses and waveguides). The detected light signal is imported and amplified in real time and triggers the piezoelectric actuator so that the targeted samples are directed into desired reservoir for subsequent advanced analysis. The real-time, closed-loop control system is developed with field-programmable-gate-array (FPGA) implementation. The system enables high-throughput (1- 10kHz operation), high reliability and low-powered (<1mW) fluorescence activated cell sorting (FACS) on a chip. The microfabricated flow cytometer can potentially be used as a portable, inexpensive point-of-care device in resource poor environments.

808nm high power diode lasers, which is rapidly maturing technology technically and commercially since the introduction in 1999 of complete kilowatt-scale diode laser systems, have important applications in the fields of industry and pumping solid-state lasers (DPSSL). High power and high power conversion efficiency are extremely important in diode lasers, and they could lead to new applications where space, weight and electrical power are critical. High efficiency devices generate less waste heat, which means less strain on the cooling system and more tolerance to thermal conductivity variation, a lower junction temperature and longer lifetimes. Diode lasers with Al-free materials have superior power conversion efficiency compared with conventional AlGaAs/GaAs devices because of their lower differential series resistance and higher thermal conductivity. 808nm GaAsP/GaInP broad-waveguide emitting diode laser bars with 1mm cavity length have been fabricated. The peak power can reach to 100.9W at 106.5A at quasicontinuous wave operation (200μs, 1000Hz). The maximum power conversion efficiency is 57.38%. Based on these high power laser bars, we fabricate a 1x3 arrays, the maximum power is 64.3W in continuous wave mode when the current is 25.0A. And the threshold current is 5.9A, the slope efficiency is 3.37 W/A.

This research investigated the effects of optical feedback on the current-driven polarization switching (CDPS) of VCSELs which exhibit significant polarization-switching hysteresis loop in L-I curve. Experimental results indicated that optical feedback can increase the bandwidth of CDPS. For VCSELs which exhibit wide polarization-switching hysteresis loop, the extension of CDPS bandwidth is limited by the time required to modulate the current to cross the width of the hysteresis loop. Accordingly, the optical feedback configuration which results the narrowest hysteresis loop will conduct the largest bandwidth extension.

As a key nonreciprocal device, the optical circulator builds optical links to several terminals in a circulating manner. The waveguide-type circulator with port count more than four has not been discussed, mainly due to the strict phase matching and adjustment. In this paper, a six-port optical circulator is proposed by introducing the nonreciprocal phase shifts (NPS) into a 3×3 multimode interference coupler. The structure with Ce:YIG material bonded to SOI waveguide is employed to illustrate the implementation and do the device simulation. There is no complex phase matching in the whole design. Good performance can be expected with the present fabrication techniques. This design scheme can also be easily generalized to the circulators with even more terminals.

In this work, we have analyzed, fabricated and demonstrated concentric micro-ring resonators in silicon-on-insulator (SOI) structure for enhanced transmission notches. The operation principles of the concentric ring resonators are studied by time-domain coupled-mode theory. Directional coupling between concentric rings offers another freedom in designing deep notch optical filters and ultra-sensitive biosensors. The finite-difference-time-domain (FDTD) simulations have shown the improvement of the notch depth, evenly distributed mode field and the effect of the resonance shift. The device is demonstrated in silicon-on-insulator structure. Transmission notch depth improvement of ~ 15dB is demonstrated for the 21-20.02-μm-radius double-ring structure comparing with the single 21-μm-radius ring.

We study the electrical and optical characteristic of the width-reduced line-defect photonic crystal waveguides with lateral p-i-n structures on Silicon-on-Insulator substrates. A longitudinal-section-based electrical model is built to take the holes into consideration. Compared with the classical line-defect photonic crystal waveguides, the width reduced photonic crystal waveguide has much stronger capacity in optical confinement in plane, which can allow a narrower intrinsic layer that leads to a fast electric response.

Integrated visible/infrared dual-band filter array is the key component of compact, lightweight, rigid miniature dual-band CCD sensing system. Interference cut-off filter array and interference absorbing filter array have been designed for infrared and visible pass band respectively. A simple, effective and compatible with high temperature deposition process lift-off technique for striping thick infrared film was investigated. Integrating photolithography, ion beam assisted electron beam physical vapor deposition and improved lift-off process, dual-band microfilter array with good performance was fabricated on the same sapphire substrate consecutively. Details of design and fabricating procedure are elucidated, and experimental results are presented.

The interactions between the optical light and sub-wavelength structures in metal film have sparked great interest on surface plasmon polaritons (SPPs). One effective way to interpret these phenomena is to make use of the phase shift between the SPP excited and the incident wave. Many theoretical and experimental studies have shown that this shift approximate to π is intrinsic at normal incidence. In this paper, the phase shift at oblique incidence is analyzed and used to interpret the transmission effect for the first time to our knowledge. A simplified 2D scattering formulation using vector finite element method is set up. Simulations show the phase shift can be approximate to π over a large range of incidence angles. With this shift, the conditions for the enhanced or suppressed transmission and the corresponding destructive or constructive interference of SPPs at oblique incidence are achieved. The transmission effect for incidence angle not satisfying these conditions, as well as its potential applications is also discussed.

AlInGaN Quaternary Alloys were successfully grown on sapphire substrate by radio-frequency plasma-excited molecular beam epitaxy (RF-MBE). Different Al content AlInGaN quaternary alloys were acquired by changing the Al cell's temperature. The streaky RHEED pattern observed during AlInGaN growth showed the layer-by-layer growth mode. Rutherford back-scattering spectrometry (RBS), X-Ray diffraction (XRD) and Cathodoluminescence (CL) were used to characterize the structural and optical properties of the AlInGaN alloys. The experimental results show that the AlInGaN with appropriate Al cell's temperature, could acquire Al/In ratio near 4.7, then could acquire better crystal and optical quality. The samllest X-ray and CL full-width at half-maximum (FWHM) of the AlInGaN are 5arcmin and 25nm, respectivly. There are some cracks and V-defects occur in high-Al/In-ratio AlInGaN alloys. In the CL image, the cracks and V-defect regions are the emission-enhanced regions. The emission enhancement of the cracked and V-defect regions may be related to the In-segregation.

Un-cooled single mode operation of 1310 nm and 1490 nm DFB (distributed feedback) lasers across a wide temperature span of 180 °C and 170 °C has been demonstrated. The lasers showed excellent performances such as high output power and high modulation bandwidth as well. This makes them ideal candidates for G-PON (Giga bit rate passive optical network) application as key components for ONU (optical network unit) and OLT (optical line terminal).

We present, for the first time, comparative studies of laser performance in the mixed vanadate crystals Nd:Y_xGd_1-xVO₄ with direct and indirect pumping. The resulting highly efficient miniaturized laser has potential for laser communications.

Ultrafast all-optical switch based on intersubband transitions in InGaAs/AlAs/AlAsSb quantum well is described. Because of very fast intra-band relaxation in conduction band, we can obtain very fast response of around 1ps. The operation principles and characteristics as an absorption saturation type device are described. Also described is the operation as an all-optical phase modulator. With Mach-Zehnder interferometer configuration, error free all-optical demultiplexing operation from 160-Gb/s to 40-Gb/s was achieved.

By analyzing the ground eigenstates of an InGaAs/InAlAs symmetric coupled quantum well for zero applied electric field and their changes along with an applied electric field, we find its advantages and disadvantages when it is applied to optical switching device. Hence a novel coupled quantum well structure is put forward. To obtain polarization independence, a tensile strain is applied to the quantum well layer. In the case of low applied electric field (F=15 kV/cm) and low absorption loss (for TE mode, α=55.56cm^-1; for TM mode, α=75.58cm^-1), a polarization-independent large electric-field-induced refractive index change (for TE mode, Δn=0.0108; for TM mode, Δn=0.0107) is obtained in the optimized InGaAs/InAlAs coupled quantum well structure at operating wavelength (λ1550nm). The large refractive index change obtained with the optimized InGaAs/InAlAs coupled quantum well under so low absorption loss and applied electric field is very attractive for the semiconductor optical switch device. This manifests the optimized coupled quantum well structure has a great potential for application to ultra-fast and low-voltage optical switches and traveling wave modulators.

The importance of photonic technologies for the European economy is recognized by the European Union and enjoys continued support. The mechanisms of the European Union to support research and development by introducing the "7th European Framework Program for Collaborative Research" are outlined. The topical content of the Framework Program is presented, as well as its implementation and in particular the support of photonic components related research and development. We will highlight the importance of the collaborative European effort and give examples of its impact. We will then provide an overview of the current topics supported by the European Commission. We will conclude by presenting the long term vision and giving indications on the likely research priorities for Photonic Components in the ICT Workprogram 2009-2010 of the 7th Framework Program (FP7).

Bismuth titanate, Bi4Ti3O12 (BTO), is a typical ferroelectric material with useful properties for optical memory, piezoelectric and electro-optic devices. Its nano-crystals were compounded by the chemical solution decomposition (CSD) technique. The structure and size of BTO were analyzed by X-ray diffraction (XRD) and transmissive electron microscopy (TEM). Three sorts of composite films BTO/PEK-c with different BTO concentration were prepared by spin-coating method at certain conditions. In this article, the scattering losses in thin films were obtained using the photographic technique. The losses in the films with different BTO weight ratios were compared and analyzed.

We report on the design of porous silicon based polarization band-pass filters, which is not only have excellent optical properties with p-polarization transmittance and s-polarization reflectance in the NIR field, but also can be used for excellent biosensor and gas sensing applications.

The glass samples of SiO₂-Al₂O₃-CdO-Li₂O-K₂O-Na₂O with different Nd³⁺-doped concentration are prepared by high-temperature solid-state reaction method, and test the absorption spectrums as well as emission spectrum excited at 488 nm, 532 nm and 808 nm. The third-order optical nonlinear properties of glasses samples are investigated by the z-scan technique. With the increment of doping concentration of Nd³⁺, the third-order nonlinear refractive index and the absorption index increase, so it belongs to the self-focusing and reverse saturated absorption medium. The glass samples open a outlook of application for nonlinear optical medium and excellent luminescence materials.

We have prepared (40SiO₂-14Al₂O₃-(40-x) CdO-2Li₂O-2K₂O-2Na₂O -x Eu₂O₃) cadmium aluminium silicate glasses doped with europium by high temperature solid-state reaction method. The absorption spectra, excitation spectra, emission spectra are obtained. With the increase of Eu₂O₃, the absorption peaks are founded increasing to the best doped concentration and then reducing, which is nonlinear relationship. The charge-transfer band is moved to 320 nm due to the addition of Cd²⁺. We can see that the ratio of peak in 591 nm and 615 nm is 0.6-0.75 in general, and is unrelated to doped concentration. By changing concentration of Eu³⁺.We can adjust and mix different intensity of light according to the demand.

The theoretical model considering nonlinear effects in the external cavity semiconductor laser with sampled fiber grating has been presented. Such effects are including the asymmetric side mode suppression ratio (SMSR) or power characteristics, and hysteresis phenomena. This theoretical model is based on the transmission line theory on compound cavity. The parameters of the laser, e.g. active section length and phase section length, have been optimized to suppress such nonlinear effects, which makes the device control simple and reliable, while the performances such as 16nm tuning range, 40dB SMSR, 8.5mW output power can be maintained.

LD-pumped all-solid-state yellow laser based on frequency-doubled Nd:YVO₄ crystal self-Raman laser was demonstrated. Through extracavity frequency-doubling with KTP crystal, the maximum average output power of the yellow laser was measured to be 495 mW with the incident pump power of 18 W. The corresponding optical conversion efficiency was about 2.75 %. The highest pulse energy, the shortest pulse width and the highest peak power of the yellow laser were obtained to be 19.9 μJ, 4.5 ns and 3.88 kW, respectively.

We present in this paper the fabrication and characterization of thermally stable double line waveguides in Z-cut periodically poled Lithium Niobate crystals. The waveguides were fabricated by using a femto-second laser, and utilized for second-harmonic generation. Our experiments have shown that a quasi-phase matching wavelength of 1548.2 nm, a tuning bandwidth of 2 nm, and a tuning temperature range of 150.4±1.6°C can be achieved.

Using an improved borosilicate glass with small third-order optical nonlinearities, i.e., nonlinear refractive index (NLRI) and nonlinear absorption coefficient (NLAC), as the matrix and comparative glass, two types of Ho³⁺-doped glass are prepared with a solid-phase smelting process at a relatively low temperature, and their third-order optical nonlinearities are measured by the closed-aperture Z-scan technique using nanosecond laser pulses at 532nm wavelength. It is found that the matrix glass possesses a positive third-order NLRI and a positive third-order NLAC, and both the third-order NLRI and NLAC of Ho³⁺-doped glasses are one order larger than those of the matrix glass, respectively. Also, an open-aperture Z-scan experiment and an optical limiting experiment further demonstrate that the Ho³⁺-doped glasses have a high third-order NLAC. All the experimental results show that this Ho³⁺-doped glasses have good protection performance for the 532nm-laser.

Motivated by the recent progresses in one-atom laser and single-molecule manipulation, this work presents the model and simulations of a single dye molecule laser device, which consists of a single dye molecule as an acceptor in a microcavity pumped by multiple donors via the intermolecular resonance energy transfer mechanism. The photon intensity is calculated at the emission peaks of donor and acceptor dyes for different pump rates and donor numbers. Finally, it is demonstrated that stimulated emission gains a distinct advantage over spontaneous emission under appropriate conditions. This work would have many important applications in a wide range of fields from physics and chemistry to nanotechnology in future.

A novel 980nm bottom-emitting VCSELs array with high power density and good beam property of Gaussian far-field distribution is reported. This array is composed of 5 symmetrically-arranged elements of 200&μm,150μm and 100μm-diameterμwith the center spacings of 300μm and 250μm respectively. The maximum power is 880mW at a current of 4A, corresponding to 1KW/cm² average optical power density. The differential resistance is Ω with a threshold of 0.56A. The novel array is compared with a 300μm-aperture-size single device and a 4*4 2-D array with 50μm element aperture size and 250μm centre spacing. The three devices have the same lasing area. The conclusion is that the novel array is better in the property of output power, threshold current, lasing spectra, far-field distribution etc.

In this paper, we briefly summarize the theory of transformation optics and introduce its application in achieving perfect invisibility cloaking. In particular, we theoretically show how the task of realizing cylindrical invisibility cloaks can be eased by using either structural approximation or material simplification. The corresponding invisibility performances of the approximate or simplified cylindrical cloaks are presented in detail.

Liquid crystal modulator(LCM) is now widely applied, especially in optical telecommunication networks. However, according to the electro-optic characteristic of liquid crystal, we will obtain nonlinear phase response when LCM is driven by the voltage varying with time linearly(v=kt+v0). And in practical application this nonlinear phase response will affect the modulation precision, communication modulation efficiency and so on. This paper presents a logarithm driving signal model to linearize the nonlinear phase response of LCM between 0 and π. When driven by a periodic signal whose voltage varies from 2.0 to 10.7V in the way of logarithm in every periods, the LCM's phase response hops in the point of intersection of two voltage periods. Therefore, we advance another periodic logarithm driving signal, whose voltage ascends from 2.0 to 10.7V in first half periods and descends from 10.7 to 2.0V in the other half periods. Furthermore, We find that the degree of phase response linearization of LCM decreases with the frequency of driving signal increasing. This paper proposes mapping the nonlinear phase response to linear one to overcome this problem. The experimental results indicate that obtaining the linear phase response of liquid crystal between 0 and π with different-frequency driving signals is feasible.

We demonstrate a fiber ring laser with a dispersion compensation fiber (DCF) and a delayed interferometer (DI), which is able to switch eleven wavelengths one by one. In ring cavity, DCF supplies different effective cavity lengths for different wavelengths, DI generates a wavelength comb corresponding to the ITU grid, a flat-gain erbium-doped fiber amplifier (EDFA) provides uniform gain for each lasting wavelength, and a semiconductor optical amplifier (SOA) not only acts as active modulator, but also alleviates homogeneous broadening effect of EDFA. Stable pulse trains with a pulsewidth about 40 ps at 10 GHz have been obtained by injecting external optical control signals into the laser. Wavelength switching process among eleven wavelengths is achieved by merely tuning an intracavity optical delay line.

A compact electro-optic modulator on silicon-on-insulator is presented. The structure consists of a III-V microdisk cavity heterogeneously integrated on a silicon-on-insulator wire waveguide. By modulating the loss of the active layer included in the cavity through carrier injection, the power of the transmitted light at the resonant wavelength is modulated. ~10 dB extinction ratio and 2.73 Gbps dynamic operation are demonstrated without using any special driving techniques. The results are consistent with the theoretical simulations.

The modal expansion method is utilized to study the reflection mechanism in the total-internal-reflection (TIR) switch. Due to the confinement of the waveguide, the beam reflection within the TIR switch is completely different from that in the free space. Its essence is the degeneracy between the even and odd modes in the waveguide of the reflection region.

In this paper a novel CW laser-compatible, squint-free, continuously tunable ring resonator-based optical beamformer mechanism for a phased array receiver system is proposed and partly demonstrated. When the optical delay elements and optical signal processing circuitry are integrated on a chip, a single-chip optical beam forming network (OBFN) is obtained. The optical delay elements are ideally continuously tunable to achieve continuous control of the beam direction, and should have a flat delay and magnitude response over the signal band, to avoid distortion. In the proposed system architecture, filter-based optical single-sideband suppressed-carrier modulation and balanced coherent optical detection are used. Such architecture has significant advantages over a straightforward architecture using optical intensity modulation and direct optical detection, namely reduced complexity of the OBFN chip, and enhanced dynamic range. Measurements on an actual 1×8 OBFN chip and an optical sideband filter chip are presented. Both are realized in CMOS-compatible planar optical waveguide technology (TriPleX).

We have measured the absorption spectrum of three kind resistivity p-type silicons by backward-wave oscillator (BWO).The absorption spectrum is examined and analyzed by least square method. The refractive index, absorption coefficient, and dielectric functions of various resistivity p-type silicons are obtained in the frequency range extending from 0.23 THz to 0.375 THz. The experimental results indicate that the absorption coefficient of the p-type silicons are decreased with the resistivity increase and its least absorption coefficient equals 3.87x10^-4 cm^-1. Our results demonstrate that the applicability of the backward-wave oscillator THz absorption spectroscopy to p-type silicon characteristic analysis by calculating the absorption spectra. This work establishes the basic spectra data for the various resistivity ptype silicons are very significative to design the terahertz waveguide with low loss.

Photoluminescence of Ar+ implanted porous silicon and porous structure of Ar+-implanted silicon (porous silicon by preanodization ion implantation) at energy of middle-energy (30keV) are investigated to gain insight into the photoluminescence properties and photoluminescence mechanism. The results show that the photoluminescence intensity of Ar+ implanted porous silicon was reduced, which was attributed to the removal of surface oxygen and creation of defects that act as nonradiative recombination; And whether samples were prepared by p-type or n-type silicon wafers, the photoluminescence intensity of porous structure of Ar+-implanted silicon was enhanced that we attribute these to the enhanced formation of porous silicon microstructure induced by ion implantation and oxygen-related defects were increased.

Abstract 100 mm wafer bonding of InP-based structure and silicon-on-insulator wafers is presented with the use of a lowtemperature (300 °C) O2 plasma-assisted wafer bonding process. An efficient vertical outgassing channels (VOCs) design is developed to eliminate the fundamental obstacle of interfacial voids in bonding due to intrinsic chemical reactions. Generated gas species of H₂O and H₂ can quickly diffuse to VOCs, etched through-holes to buried oxide layer (BOX), and absorbed by the BOX layer owing to the open network structure and large gas permeability. The interfacial void density is reduced from 55,093 cm^-2 down to 3 cm^-2, more than five orders of magnitude reduction for appropriate design of VOCs. Uniform patterning of VOCs leads to no outgassing "dead zone" across the entire bonding area, and decrease of the thermal mismatch-induced interfacial strain potentially as well, which both result in the wafer scale-independent bonding. In addition, we present distributed feedback silicon lasers realized on the hybrid silicon evanescent platform. The laser operates continuous wave with a single mode output at 1600 nm. A continuous wave (CW) low threshold of 25 mA with a maximum output power of 5.4 mW is demonstrated at 10 °C. The obtained side mode suppression ratio of 50 dB, 3.6 MHz linewidth, and over 100 nm single mode operation band are comparable to those of commercial III-V DFB devices. These highly single mode lasers may find applications in computer interconnect.

High-speed AlGaInAs multiple-quantum-well (MQW) electroabsorption modulated lasers (EMLs) based on identical epitaxial layer (IEL) integration scheme are developed for 40 Gb/s optical fiber communication systems. The electroabsorption modulator (EAM) section adopts a narrow high-mesa waveguide formed by inductively coupled plasma (ICP) dry etching technique, and a self-aligned planarization technique is employed to further reduce the device capacitance. Resonances are observed in the small signal modulation response of the packaged EML module, which are attributed to parallel-plate modes of the coplanar waveguide (CPW) transmission line used for modulation signal feeding and the residual reflection at the modulator facet, respectively. The influence of such resonances on the large signal eyediagram performance of the device is studied, and methods for their suppression are presented. Clear eye opening under 40 Gb/s non-return-to-zero (NRZ) modulation has been demonstrated for the optimized EML module.

Multiple streams of high definition television (HDTV) and improved home-working infrastructure are currently driving forces for potential fiber to the home (FTTH) customers [1]. There is an interest to reduce the cost and physical size of the FTTH equipment. The current fabrication methods have reached a cost minimum. We have addressed the costchallenge by developing 1310/(1490)/1550nm bidirectional diplexers, by monolithic seamless integration of lasers, photodiodes and wavelength division multiplexing (WDM) couplers into one single InP-based device. A 250nm wide optical gain profile covers the spectrum from 1310 to 1550nm and is the principal building block. The device fabrication is basically based on the established configuration of using split-contacts on continuos waveguides. Optical and electrical cross-talks are further addressed by using a Y-configuration to physically separate the components from each other and avoid inline configurations such as when the incoming signal travels through the laser component or vice versa. By the eliminated butt-joint interfaces which can reflect light between components or be a current leakage path and by leaving optically absorbing (unpumped active) material to surround the components to absorb spontaneous emission and nonintentional reflections the devices are optically and electrically isolated from each other. Ridge waveguides (RWG) form the waveguides and which also maintain the absorbing material between them. The WDM functionality is designed for a large optical bandwidth complying with the wide spectral range in FTTH applications and also reducing the polarization dependence of the WDM-coupler. Lasing is achieved by forming facet-free, λ/4-shifted, DFB (distributed feedback laser) lasers emitting directly into the waveguide. The photodiodes are waveguide photo-diodes (WGPD). Our seamless technology is also able to array the single channel diplexers to 4 to 12 channel diplexer arrays with 250μm fiber port waveguide spacing to comply with fiber optic ribbons. This is an important feature in central office applications were small physical space is important.

We report the use of AlGaInAs quantum wells (QWs) as a saturable absorber in the Q-switching of a high-power diode-pumped Nd-doped 1064nm laser. The barrier layers are designed to locate the QW groups in the region of the nodes of the lasing standing wave for avoiding damage. With an incident pump power of 22 W at 878nm, an average output power of 6.8 W with a Q-switched pulse width of 0.85 ns at a pulse repetition rate of 105kHz was obtained.

We report a compact transmitter with 0.4 W output optical modulation amplitude at 1 Gb/s using a twin-contact directly modulated laser with a ~100 mA applied current swing and a 2 A constant bias current. Bit-error-ratio measurements confirm high signal quality for optical wireless communication applications.

A blue-violet enhanced BDJ photodetector which can simultaneously determine the centroid wavelength and the radiant power of LEDs from 380 to780nm was investigated, and its application in the color measurement and the white balancing of RGB white LEDs was demonstrated. This BDJ photodetector directly gave the chromatic coordinates of a LED that was approximated as a monochromatic stimulus due to its narrow spectrum compared with the CIE colormatching functions. Maximal simulated and experimental errors Δ'u'v' to the target white point of the white balanced RGB LEDs was 0.0154 and 0.0214. The BDJ photodetector also performed to be sensitive to the spectrum variation characterized by CCT, and was preferable as a sensor for monitoring the white point.

A free-standing nanopillar with a diameter of 300 nm, and a height of 2 μm is successfully demonstrated by focused ion beam milling. The measured micro-photoluminescence (μ-PL) from the embedded InGaN/GaN multiple quantum wells shows a blue shift of 68 meV in energy with a broadened full-width at half maximum, ~200meV. Calculations based on the valence force field method suggest that the spatial variation of the strain tensors in the nanopillar results in the observed energy shift and spectrum broadening. Moreover, the power-dependent µ-PL measurement confirms that the strain-relaxed emission region of the nanopillar exhibits a higher radiative recombination rate than that of the as-grown structure, indicating great potential for realizing high-efficiency nano devices in the UV/blue wavelength range.

High efficiency GaN-based light-emitting diodes (LEDs) are demonstrated by a nanoscale epitaxial lateral overgrowth (NELO) method on a SiO₂ nanorod-array patterned sapphire substrate (NAPSS). The SiO2 NAPSS was fabricated by a self-assembled Ni nano clusters and reactive ion etching. The average diameter and density of the formed SiO2 nanorod-array was about 100 to 150 nm and 3 x 109 cm^-2. The transmission electron microscopy images suggest that the voids between SiO₂ nanorods and the stacking faults introduced during the NELO of GaN can effectively suppress the threading dislocation density. The output power and external quantum efficiency of the fabricated LED by NELO method on NAPSS were enhanced by 52% and 56% respectively, compared to those of a conventional LED. The improvements originated from both the enhanced light extraction assisted by the NAPSS, and the reduced dislocation densities using the NELO method.

We have demonstrated a novel approach to achieve a stable multi-wavelength laser system (MWLS) which is making use of a quantum dot semiconductor optical amplifier (QD SOA) as a highly birefringence material and an optical polarizer at the same time. Both the channel frequency spacing and the central lasing wavelength of the QD MWLS can be accurately set by using the desired-designed QD SOA with the certain operation conditions and by setting the polarization controller properly. The detailed working principles and the experimental results have been reported in this paper. The proposed QD MWLS technology can be used for characterizing the intrinsic properties of the QD semiconductor waveguide materials that could also be used for spectral narrowing of a laser system. We have experimentally confirmed that the QD SOA is highly inhomogeneous gain material as compared with QW SOA.

We report the preparation of silicon nanocrystals with efficient ultraviolet luminescence by nanosecond pulsed laser ablation in de-ionized water at a high laser fluence condition. Atomic force microscopy results show that nano-grains form in the process of laser ablation. Fourier transform infrared spectroscopy analyses indicate that silicon nanocrystals are formed and partially oxidized during synthesis. The photoluminescence measurement and the ultraviolet-visible transmittance spectroscopy of the samples prepared at various fluences reveal that all the prepared samples present an efficient ultraviolet emission at room temperature and it can be attributed to the quantum confinement effect and surface defect states. The emission wavelength of silicon nanocrystals is far shorter than visible light, which means potential applications in optoelectronic devices.

An InGaAsP/InP 2×2 Mach-Zehnder interferometer (MZI) optical switch based on multimode interference (MMI) couplers was presented. The switch characteristics were simulated using a three-dimensional beam propagation model. The switch structure was designed to be single mode operation and insensitive to polarization. The light signal can be switched from cross port to bar port with an injection current of 43mA by carrier modulation on the principle of injection free carriers, bend-filling effects and bandgap shrinkage. The measured crosstalk is -19.2dB and -14.3dB at the on and off state, respectively. This optical switch can be easily integrated with other active devices and has potential application in future DWDM and OXC systems.

All-optical wavelength converters (AOWCs) based on nonlinear processes of semiconductor optical amplifiers (SOAs) have attracted interest to overcome the wavelength blocking issues in future transparent networks. While many schemes work well, pattern effect impairments that are due to the finite lifetime of charge carriers are an issue most of the time. Recently, wavelength conversion and pattern effect mitigation techniques that work by properly shaping the passband of filters following the converter have been introduced. However, due to the necessity of selecting filter slope and position precisely, one would expect that the schemes are extremely sensitive to any drift of the center wavelength. In this work, we demonstrate a 40 Gbit/s SOA-based wavelength converter with more than 15 dB dynamic input power range. In addition, the center wavelength of the converted signal has a tolerance of ~0.2 nm towards the red spectral region and of ~0.1nm towards blue spectral region, respectively. This success is due to combining advantageously pattern effect mitigation techniques connected to the pulse reformatting optical filter, the red-shift and the blue-shift optical filter.

This communication addresses, theoretically and experimentally, the effect of the cross polarization modulation (XPolM) phenomenon on the performance of a wavelength converter based on a four wave mixing process (FWM) developed in a semiconductor optical amplifier (SOA). The main studied parameter for evaluating the performance of the wavelength converter is the conversion efficiency, whose degradation, provoked by the XPolM, is analyzed when the four wave mixing process is developed with input signals linearly co-polarized at 0, 45, 90, and -45 degrees. The analysis is based on the theoretical and experimental determinations of the polarization mismatch of the pump and probe signals. Finally, it is demonstrated that classic models lacking the inclusion of the XPolM effect can reflect a significant error in the estimation of the conversion efficiency of a wavelength converter based on FWM.

All-optical wavelength conversion is considered to be a key technology in future high-speed large-capcity dense wavelength-division-multiplexed (DWDM) optical networks. Transparent wavelength conversion is highly desired especially for various advanced modulation formats. We report a novel 40 Gbit/s all-optical transparent frequency-shift keying (FSK) wavelength conversion and logic NOT gate by exploiting cascaded second-harmonic generation and difference-frequency generation (cSHG/DFG) in a periodically poled lithium niobate (PPLN) waveguide. In addition, transparent wavelength conversions for optical duobinary (ODB) and alternate-mark inversion (AMI) modulation formats are demonstrated in the experiment.

A phosphor-conversion white light using an InGaN laser diode that emits 405 nm near-ultraviolet (n-UV) light and phosphors that emit in the red/green/blue region when excited by the n-UV light was fabricated. The relationship of the luminous flux and the luminous efficacy of the white light with injection current were discussed. Based on the evaluation method for luminous efficacy of light sources established by the Commission International de I'Eclairage (CIE) and the phosphor used in this experiment, a theoretical analysis of the maximum luminous efficacy of this white light fabrication method were also presented.

As the increasing applications of the semiconductor lasers in the laser processing, the single 2-D stack optic-power density has not satisfied the actual requirements. It demands to couple several diode laser stack beams to one to improve the brightness, and it becomes the central issue to adopt the appropriate beam coupling technology which would offer high quality and high efficiency. In this paper, it mainly introduces the beam shaping and the technology of spatial coupling, polarization coupling, and wavelength coupling. The coupling key elements are presented and indicated. Finally, the development of the diode laser on beam coupling in our country fell behind through analyzing the statement of the world. Our lab is studying on polarization coupling and wavelength coupling. We gain some results by phase,d which the polarization coupling efficiency can achieve 90% for two LD stacks with seven bars whose luminous wavelength is 975nm and980nm. By two 808nm diode laser coupling effeice the efficiency of 60% can be achieved after focusing to the beam size of 2x2mm².

Two-segment semiconductor optical amplifier (SOA) is proposed and studied to manipulate the gain and saturation characteristics of SOA; this kind of SOA is separated into two segments that are electrically insulated from each other by two split electrodes; the two segments share the same active region and other internal structure. By changing the injection current density of the front segment or back segment, the saturation output power, bandwidth and gain compression can be easily controlled. Therefore it is convenient for SOA to meet various application requirements in optics communication.

Based on the framework of the spin-flip model (SFM), for the GHz level modulation frequency, the polarization performances of current-modulated vertical-cavity surface emitting lasers (VCSELs) subject to weak optical feedback have been theoretically investigated. The results show that, for type I polarization switching (PS), under small signal modulation, the variation of the modulation frequency does not affect the polarization direction of the VCSEL output, but due to the influence of the optical feedback, the VCSEL output may behave period, doubling period and chaos state with modulation frequency variation. For the case of the large signal modulation, optical feedback can result in the generation of a new style of PS with the variation of the modulation frequency.

Temporal-Spectral Imaging of optical pulses constitutes a technique for the measurement of fast optical spectral. The experiment to perform real-time spectral analysis of optical pulses in fibre by time lens is demonstrated in this article. The use of time lens in the demodulation of the grating wavelengths is discussed in this article.

The signal intensity is derived firstly on the basis of point spread function. Then the effect of pinhole radius on resolution is discussed for different central obstruction rate ε. According to the simulated plots, the optimum relationship of axial resolution to pinhole radius and central obstruction rate ε is proposed. Finally the confocal imaging system is designed and established. The axial response is measured for different pinhole radius. Experimental results agree well with theoretical analysis. The in-focus images of bar target is obtained by the confocal imaging system which shows good performance

There has been a rapidly increasing demand for the high numerical aperture (NA) in specialty optical fibers used in recent high power fiber lasers and remote sensing applications. Various polymer clad resins (PCR) have been reported aimed for a low refractive index to achieve a high NA, which resulted in a lower modulus. In this study, we report a novel PCR with a higher modulus whilst maintaining a high NA over 0.44 using newly designed fluorinated oligomer and monomer having low refractive index and high functionality. Some resins prepared various formulations using synthesized oligomers and then compared curing speed.

The optical diffraction efficiency of lithographic grating was probed in this study. The enhanced first order spectral diffraction efficiency emerged from localized surface-plasmon excitation of gold nanoparticles which are alternatively uniformly and randomly spread in grating strips. The sensible measurement more than traditional method is reported.

The properties of crossing for two perpendicular subwavelength plasmonic slot waveguides are theoretically investigated. Results show when encountering a nano intersection the crosstalk for the direct crossing is around 25%, almost the same as throughput. In terms of symmetry considerations and resonant-tunnelling effect, we design two types of compact cavity-based structures. Our results show that the crosstalk is eliminated and the throughput reaches the unity on resonance. Simulation results are in agreement with those from coupled-mode theory. Taking material loss into account, the symmetry properties of the modes are preserved and the crosstalk remains suppressed. Our results may open a way to construct nanoscale crossings for high-density nanoplasmonic integration circuits.

A variety of metamaterials has been demonstrated recently that support backward waves and negative refraction (Negative Index Materials, NIM.) In particular, these materials enable sub-wavelength resolution that makes them even more interesting, especially in optical domain rather than at microwave frequencies where their unusual properties were known for decades. We describe below theoretical and experimental studies of the so-called 'fishnet' metal-spacer holearray metamaterials, which exhibit NIM behavior at optical frequencies, having unit cell size of a few 100s nm. We demonstrate experimentally that their refractive index can be modulated very fast and very strongly (from -2.4 to -1.5) around the communication wavelength of λ1.55 um, in good agreement with the FDTD results. We also discuss a problem of loss compensation in those materials with hefty Ohmic losses by using gain media and local field enhancement in metallic nanoparticles ensembles that enable SERS.

We have demonstrated femtosecond pulses from a passive single-section monolithic InAs/InP quantum-dot (QD) semiconductor laser with the active length of 456 µm and the ridge width of 2.5 µm in the C-band wavelength range from 1528 nm to 1565 nm. The transform-limited Gaussian-pulses are generated at the 92-GHz repetition rate with the 312-fs pulse duration without any pulse compression scheme. The average output power is larger than 13.2 mW for the injection current of 60 mA. And the lasing threshold current and external differential quantum efficiency are 17.2 mA and 38%, respectively. The mode-beating linewidth of the proposed QD mode-locked laser (MLL) was measured less than 20 KHz. We have interpreted that four-wave-mixing (FWM) process and other nonlinear effects within the QD waveguide gain materials make the major contributions to lock the phase the longitudinal modes of the QD Fabry-Perot cavity together to achieve this strong self-pulsation process.

In this paper, size-tunable PbS semiconductor quantum dots were synthesized by sol-gel route and a novel optical fiber amplifier was proposed. Based on fused tapered fiber coupler, the PbS quantum dots film was deposited in the couple region and evanescent wave coupled semiconductor quantum dots fiber amplifier was fabricated. Due to the thinned fiber shape, evanescent wave penetrates into outer surface. When the pumped light are propagated in the evanescent field area, the evanescent wave of pumped light is absorbed by PbS quantum dots, so the PbS quantum dots are excited from ground state to excited state. And when the signal light are propagated in the evanescent field area, the evanescent wave of signal light stimulate PbS quantum dots, the quantum dots return to ground state and release photons which have the same frequency and phase with signal light. With interaction between the evanescent wave power and the coated PbS quantum dots film, the light can be amplified. The optical amplification was obtained at 1310nm wavelength with 980nm wavelength LD as pump.

The properties of guided plasmon polaritons supported by a triangular metallic waveguide are presented. The waveguide examined is a metal core with equilateral triangular cross section embedded in an infinite lossless dielectric media. Based on the rotation symmetry of the waveguide, the sketch of the supported fundament modes is given. The fundamental modes can be constructed by a proper combination of the corner modes and surface modes, which can be supported by isolated metal corners and metallic-dielectric interface respectively. The mode properties of the metallic waveguide, e.g., the dispersion and propagation length with the size of the metal core, mode field orientation and field distribution profiles are addressed by using a finite element method. The numerical singularities of the optical field are removed by smoothing the corners with an appropriate arc at the nano meter scale. The guided modes supported by the structure are determined and characterized for both subwavelength and suprawavelength. We find that the corner modes exist in both regimes, while the surface modes only appear in the suprawavelenth. Our results also show that the mode properties preserve a certain kind of symmetry of the waveguides. The degenerate modes exist both for the corner guided modes and for surface guided modes. The first fundamental corner modes is a polarization-independent mode without the cut-off size of the waveguides. Calculations also show how sensitively the mode changes with the corner sharpness. The propagation constant of the corner modes is sensitive to the corner sharpness, while the side modes are unaffected.

The reflectance and transmittance of thin films at oblique incident angles exhibit strong polarization effects, particularly for the films inside a glass cube. However, the polarization effects are undesirable in many applications. To solve this problem, non-polarizing beam splitters with unique optical thin films have been achieved employing a method of combination of interference and frustrated total internal reflection, the non-polarizing condition expressions based on frustrated total internal reflection has been derived, and the design examples of non-polarizing beam splitters with an optimization technique have been also presented. The results of Rp=(50±0.5)%, Rs=(50±0.5)% andΔr=(0±0.3) degree in the wavelength range of 400-700nm have been obtained. The thickness sensitivity of NPBSs is also analyzed.

In the present paper, the properties of an antenna centred at a metamaterial slab with zero permittivity are investigated. It is analyzed that the antenna can achieve high directive performance. Its half power beam width (HPBW) decreases monotonically with the increase of the width of the slab. While the gain of such antenna can only be 0dB independent of the slab's width. When the permittivity deviates form zero to a little positive number, antenna can achieve high gain by choosing appropriate slab's width due to the transmission resonance. The effect of loss is also analyzed.

We investigate the polarization-dependent mode gains and polarization rotation (PR) of the semiconductor optical amplifier in pump-probe scheme, and find that the relationship between polarization rotation (PR) and mode gains keeps well under different pump power. Thus we can simply obtain the PR angle by measurement of the mode gains. Choosing suitable injected current we realize the orthogonal polarization rotation by pump laser with power of ~3.5 mW. Then we propose a novel digital polarization encoding scheme and perform it well in a 10-km fiber transmission system with data rate at 2.5 G-bit/s, which is promising to promote the optical power-equalized encoding communications.

Characteristics of GaN-based photonic crystal surface-emitting lasers (PCSELs) were investigated and analyzed. We demonstrated two different lattice constant of the GaN-based PCSEL. One with lattice constant of 290nm emits a blue wavelength at 401.8 nm with a linewidth of 1.6 Angstrom and shows a threshold energy density about 2.7 mJ/cm² under the optical pumping at room temperature. The other with lattice constant of 234nm observed a wavelength at 423.8nm with a linewidth of 1.1 Angstrom and energy density about 3.5 mJ/cm2. The laser emission covers whole circularly 2D PC patterns (50 µm in diameter) with a small divergence angle. The lasing wavelength emitted from 2D PC lasers with different lattice constants occurs at the calculated band-edges provided by the PC patterns. The characteristics of large area, small divergence angle, and single mode emission from the GaN-based 2D surface-emitting PC lasers should be promising in high power blue-violet emitter applications. The lasing wavelength emitted from PCSELs with different lattice constants occurs at the calculated band-edges showing different polarization angles due to the light diffracted in specific directions, corresponding exactly to Γ, K, and M directions in the K-space. Furthermore, the PCSEL also shows a spontaneous emission coupling efficiency β of about 5x^10-3 and a characteristic temperature of 148K.

A novel scheme for an ultrahigh-speed all-optical full adder based on dual-pump four-wave mixing (FWM), including parallel dual-pump FWM and orthogonal dual-pump FWM, in two semiconductor optical amplifiers (SOAs) is proposed. In this scheme, the polarization-shift-keying (PolSK) modulation format is used, so pattern-dependent degradation can be reduced. The proposed all-optical full adder is simple, compact, and can accommodate ultrahigh-speed operation. By numerical simulation, it is theoretically investigated using the broad-band dynamic model.

Based on the frustrated total internal reflection theory, a leaky large-mode-area double clad fiber is designed. The propagation constants and leakage loss of the fundamental mode LP₀₁ and sub-low order mode LP₁₁ is investigated by using of the matrix method. Results show that the designed fiber can operate with single-mode.

The self-collimation frequencies (SCFs) in two-dimensional photonic crystals (2-D PhC) have been investigated systematically by the plane-wave expansion method. In the wave-vector space, the square-lattice 2-D PhCs have some square-shaped equifrequency contours (EFCs) both for TE modes and for TM modes. Narrow-beam lights with these frequencies can propagate in the directions normal to the flat borders of the EFCs without any significant broadening, which is known as self-collimation effect. We consider the 2-D PhCs consisting of a square lattice of air cylinders in a dielectric material and the 2-D PhCs consisting of a square lattice of dielectric cylinders in air respectively. Calculation results show how SCFs of TM and TE modes change with the radius of cylinders and the refractive index of the material. These results can be applied to designing the PhC devices based on self-collimation effect.

In this paper, a high detectivity THZ-IR photodetector based on resonant tunneling spherical centered defect quantum dot (RT-SCDQD) is investigated. Inserting the centered defect in quantum dot, increases the dipole transition matrix element and so increases the absorption coefficient considerably (1.05x10⁶~7.33x10⁶ m^-1 at 83μm). Therefore the quantum efficiency in SCDQD structure enhances which leads to increasing the responsivity of the proposed system. We propose a method for implementation of this complex quantum dot. Attaching the resonant tunneling double barrier to the quantum dot removes the basic problem of electron collection from deep excited state without applying large bias voltages. Also, application of the double barrier reduces the dark current. These improvements conclude to ultra high detectivity of 2.25x10⁹ cmHz^1/2/W at 300°K and 83μm respectively.

Electro-optic properties of a cross-linked second order nonlinear optical polymer were reported. This polymer was synthesized via the crosslinking reaction with cross linker Trimethylolmelamine by doping the chromophores into the cellulose diacetate system. The crosslinking temperature is 144°C. The electro-optic coefficient was measured to be 7.12 pm/v at 1550 nm after poling. The stability characteristic of electro-optic effects was studied by a combination of the electro-optic coefficient and dielectric relaxation measurements. Results show that the cross-linked electro-optic polymer system possesses an excellent long-time stability. The average relaxation time is as large as 5880 days and the relaxation was modeled by KWW equation. The dielectric analyses show that the temperature dependence of the relaxation time follows Arrhenius law.

The pump structure greatly influences the characteristics of a diode side-pumped laser. To achieve high absorption efficiency and a homogeneous pump-beam distribution simultaneously, a systemic algorithm has been established to optimize the pump structure, where multiple reflections occur on the internal wall of the reflector inside the pump chamber. The absorption efficiency and the deviation of the absorption distribution are both evaluated for a typical solid-state laser medium. A scheme for identifying an ideal pump configuration was finally obtained from several determination procedures, in which all pump structure parameters were taken into account. A novel design of an efficient, highly reliable, and good beam quality diode side-pumped solid-state laser is presented. Effort has been done to obtain a highly uniform pumping intensity in the active area, which simultaneously reduces the effects of thermal gradient. In this design a novel lens duct configuration is used. By this way a uniform power distribution and a maximum absorption of pump power is resulted. Numerical analysis also indicates the superiority of the design to other methods such as direct and diffusive pumping techniques.

The dynamics of a semiconductor laser with delayed optoelectronic feedback are theoretically investigated when the delay time is continuously varied. The results show that, for a fixed feedback time, the output dynamics state of the semiconductor laser with delayed optoelectronic feedback is dependent on the continuous variation route of delay feedback time; the bistability can be obtained for a given varying range of the delay feedback time. Further more, by adding modulation signal, the characteristics of the bistability states become more complex, and some new types of dynamic bistability states are observed.

Based on the theory describing the optical feedback semiconductor lasers (SLs) under optical injection, the effects of the feedback strength and delay time, injected strength and frequency detuning on the self-correlation performance of the output chaotic signal are investigated. The results show that the full-width at half-maximum (FWHM) and peak sidelobe level (PSL) of the output self-correlation function is critically dependent on parameters related to injection and feedback. By reasonably selecting the parameters, the self-correlation function with 0.02ns FWHM can be obtained, which is prior to reported results.

The cadmium silicate glass samples of 40SiO₂-14Al₂O₃-(40-x) CdO-2Li₂O-2K₂O-2Na₂O-xEr₂O₃ (x=0.15, 0.20, 0.25, 0.30, 0.35, 0.40 mol) was prepared by high-temperature solid-state reaction method, and it is pumped at 488 nm, 532 nm and 800 nm respectively. The results indicate that the main peak wavelengths are at 547 nm, 731 nm and 1534 nm excited at 488 nm. The relationship of the intensity between the emission light of 731 nm and Er3⁺-doped concentration is nonlinear. Near-infrared light nearby 1534 nm is excited at 532 nm and 800 nm, but it is weaker at 800 nm. The glass samples open a outlook of application for conversion luminescence materials.

The influence of bias current and ASE injection power on the side-mode suppression ratio (SMSR), relative intensity noise (RIN) and gain of the ASE-injection wavelength-locked Fabry-Perot laser diode (F-P LD) have been studied experimentally. Results show that the SMSR and RIN depend on the bias current for a given ASE, and there is different optimum bias current in terms of the SMSR and RIN. With the influence of detailed spontaneous recombination mechanism and its temperature dependence and the temperature- and wavelength-dependent material gain, we propose a static model of the wavelength-locked F-P LD based on nonlinear etalon theory. The temperature dependence of gain and saturation power of wavelength-locked F-P LD is analyzed theoretically with the model. The results show that the saturation power increases as we increase the operation temperature, while it decreases as we increase the reflectivity of front facet.

We propose and experimentally demonstrate all optical format conversion from non-return-to-zero (NRZ) format to frequency-shift-keying (FSK) format based on free carrier dispersion effect in a silicon mode-split microring resonator. The injection of the high-power NRZ signal generates free carriers leading to the blue shift of the spectrum when a '1' comes. Therefore, there is a selective filtering for the two probes with certain separation located at different position of the split mode according to the information carried by the NRZ signal. Then the NRZ signal is converted to the FSK format. The microring resonator features ultra-compact size with a radius of 10 μm thus is suitable for integration with silicon-on-insulator (SOI) based optical and electronic devices. The split mode can provide large and variable frequency deviation for the FSK signal. 1 Gb/s NRZ signal is successfully converted to FSK format with a frequency deviation of 40 GHz, which can find application for interconnection between a metropolitan area networks (MAN) and a passive optical network (PON) system.

We report a new type of high-speed electro-optic (E-O) beam scanner based on Potassium Tantalate Niobate (KTN) crystal. It has larger scanning angle, better angular resolution, and lower driving voltage comparing to the traditional E-O crystal beam scanner. Compared to conventional moving mirrors such as servo-controlled mirrors and galvanic mirrors, the demonstrated E-O beam scanner can improve the response time by 100 times. The presented device has many other unique features such as light weight, small dimension, low power consumption, and no-moving components particularly suitable for airborne and space-borne applications.

The readout integrated circuit (ROIC) for micro-bolometric infrared focal plane array (IRFPA) is commonly fabricated in silicon complementary metal oxide semiconductor field effect transistor (CMOS) technology. There are three main categories of noise in a typical CMOS ROIC, which are 1/f noise, KTC noise and fixed pattern noise. These noises in CMOS ROIC can seriously restrain the dynamic range of the ROIC and degrade the performance of IRFPA. A new CMOS ROIC for micro-bolometric IRFPA is designed to suppress the noises, and its performance is successfully verified through the theory analysis and experimental results in this paper.

High-power single-mode 980nm pump lasers are the key components in optical fiber amplifier. Thermal management for the telecom applications is a key design parameter for both package and system level. In this paper, based on the designed structural and material parameters of Epi-down bonded uncooled 980nm laser, the heat distribution of Epi-down bonded uncooled pump laser was simulated using the finite element method, and the photoelectric properties of designed and packaged module were tested. A fiber output power of 200mW was achieved for the Epi-down bonded uncooled 980nm laser with fiber Bragg grating, and module can work steadily over a wide temperature range of 0~70°C, with a small wavelength shift of 0.2nm, along with a FWHM less than 1.1nm, and a SMSR of more than 45dB.

A tunable Fourier domain mode-locked (FDML) laser is designed and realized with Semiconductor Optical Amplifier (SOA), and laser with wide tunable range and high stability could be acquired. Applying the tunable laser to fiber grating sensor system could improve Signal Noise Ratio and demodulation precision, enhance the ability of multiplexing and advance the system performance.

All-optical clock recovery (CR) from 20-Gbit/s nonreturn-to-zero differential phase-shift-keying (NRZ-DPSK) signal is demonstrated experimentally by using Polarization-Maintaining Fiber Loop Mirror Filter and semiconductor optical amplifier (SOA) fiber ring laser. Only by adjusting polarization controller (PC), NRZ-DPSK signal were conveniently and fast converted to pseudo return-to-zero (PRZ) signal via PMF-LMF. Then the PRZ signal is injected into the SOA fiber laser for CR. The recovered clock signals with the extinction ratio of 10 dB and the root-mean-square timing jitter of 850 fs is achieved under 231-1 pseudorandom binary sequence NRZ-DPSK signals measurement.

The photoluminescence (PL) spectra at room temperature for the silicon-based samples doped by Nd by ion implantation are measured. The results show that all the samples possess blue-violet photoluminescence properties under the ultraviolet light excitation and its light emission is stable. The intensity of PL spectra is closely relative to the dose of implantation and to the temperature of thermal annealing.The above samples were treated by anodization method. The PL spectra of porous samples which were treated by HNO₃ were measured. The results show light emission efficiency of the porous samples that were treated by electro-chemical anodization etch and HNO₃ is higher than those of ordinary PS samples under the same measuring conditions.

II-VI family semiconductor nanocrystals have attracted most interests in nanometer science and technology recently. The quantum dots have many applications in optoelectronic device such as LEDs for its superior properties resulting from the three-dimensional confinement effect of its carrier. Hybrid inorganic/organic electroluminescent devices were demonstrated using monolayers of CdSe/ZnS core/shell QDs sandviched between two organic thin films. However, the luminous efficiency of the hybrid in organic/organic device was very low. In this paper, an intermediate shell of CdS was used as the lattice parameter adaptation layer to improve the core/shell interface quality the luminous efficiency of the core/shell QDs. White light-emitting diodes (WLEDs) were fabricated by combining blue InGaN chips with luminescent colloidal core/shell CdSe/CdS/ZnS quantum dots (QDs). Photoluminescence of CdSe/CdS/ZnS quantum dots demonstrated high photoluminescence efficiency with a quantum yield more than 44%, and size-tunable emission wavelengths from 380 to 620nm. WLED was successfully assembled by blue InGaN chip plus green and red emitting CdSe/CdS/ZnS QDs. The InGaN chip white-light-emitting diodes with CdSe/CdS/ZnS quantum dots as the emitting layer are potentially useful in illumination and display applications.

Hydrogenated nanocrystalline SiC films have been deposited by using helicon wave plasma enhanced chemical vapor deposition (HW-PECVD) in H₂, SiH₄ and CH₄ gas mixtures at different RF powers. Their structural and optical properties have been investigated by Fourier transform infrared absorption (FTIR), atomic force microscopy (AFM) and ultraviolet-visible (UV-VIS) transmission spectra. The results indicate that RF power has an important influence on properties of the deposited films. It is found that in a 300 °C low substrate temperature, only amorphous SiC can be deposited at the radio frequency (RF) power of lower than 400 W, while nanocrystalline SiC can be grown at the RF power of equal to or higher than 400 W. The analyses show that the high plasma density of helicon wave plasma source and the high hydrogen dilution condition are two key factors for depositing nanocrystalline SiC films at a low temperature.

ZnS/CdS were deposited by chemical vapor deposition (CVD) technique on porous silicon substrates formed by electrochemical anodization of n-type (100) silicon wafer. The optical properties of ZnS/CdS porous silicon composite materials are studied. The results showed that new luminescence characteristics such as strong and stable visible-light emissions with different colors were observed from the ZnS/CdS-PS nanocomposite materials at room temperature.

Grating Light Valve (GLV) is a kind of optics device based on Micro-Opto-Electro-Mechanical System (MOEMS) technology, utilizing diffraction principle to switch, attenuate and modulate light. In this paper, traditional GLV device's structure and its working principle are illuminated, and a kind of modified GLV structure is presented, with details introduction of the fabrication technology. The GLV structure includes single crystal silicon substrate, silicon dioxide isolating layer, aluminum layer of fixed ribbons and silicon nitride of movable ribbons. In the fabrication, lots of techniques are adopted, such as low-pressure chemical vapor deposition (LPCVD), photolithography, etching and evaporation. During the fabrication processes, Photolithography is a fundamental and fatal technology, which determines etching result and GLV quality. Some methods are proposed through repeated experiments, to improve etching result greatly and guide the practical application. This kind of GLV device can be made both small and inexpensively, and has been tested to show proper range of actuation under DC bias, with good performance. The GLV device also has merits such as low cost, simple technology, high fill ratio and low driving voltage. It can properly be well used and match the demands of high light power needed in laser phototypesetting system, as a high-speed, high-resolution light modulator.

In this paper, dry etching of In_0.8Al_0.2As/In_0.8Ga_0.2As/In_1-xAl_xAs (In_1-x-yAl_xGa_yAs) epitaxy material was studied in BCl₃/Cl₂/Ar inductively coupled plasma (ICP). Etching behavior was characterized by varying the BCl₃/Cl₂/Ar mixing ratio, ICP power or DC-bias. The results indicate that, in Cl₂ dominant condition, smooth surfaces are achieved with mean etch rate exceeding 2 μm/min. As the ratio of BCl₃ increasing, the etch rates decrease monotonously and the surfaces becomes rougher because of low volatility InCl_x etch product. ICP power influences the etch rates, and the etch rates increase monotonously with DC-bias. The result is useful for the fabrication of extended long-wavelength response optoelectronic InGaAs devices.

Whispering-Gallery-Mode (WGM) photonic crystal microcavity is a kind of photonic crystal application and can potentially be used for miniaturized photonic devices, such as thresholdless lasers. In this paper we study the WGM of photonic crystal microcavities focusing on the so called H2 cavities which are formed by removing seven air holes. The WGM in these large-size cavities has some advantages compared with single defect WGM in the view of real device applications. We further add a central air hole in the cavity region to analyze the effect on WGM in the microcavity by finite difference time domain (FDTD) and plane wave expansion (PWE). It is found that the tolerance of WGM is large enough for the fabrication of electrical injection structure.

A theoretical model of wavelength interleaver, which is based on an asymmetric Mach-Zehnder interferometer (AMZI) constructed in a two-dimensional photonic crystal (2D PhC), is proposed and numerically demonstrated. The 2D PhC consists of a square lattice of dielectric cylindrical rods in air. The AMZI includes two mirrors and two splitters. Light propagates between them employing self-collimation effect. The two interferometer branches have different path lengths. By using the finite-difference time-domain method, the calculation results show that the transmission spectra at two AMZI output ports are in the shape of sinusoidal curves and have a uniform peak spacing in the frequency range from 0.191c/a to 0.200c/a. When the path length of the longer branch is increased and the shorter one is fixed, the peaks shift to the lower frequencies and the peak spacing decreases nonlinearly. Consequently, the transmission can be designed to meet various application demands by changing the length difference between the two branches. For the dimensions of the wavelength interleaver are about tens of central wavelengths, it may be applied in future photonic integrated circuits.

Under a wide range of process parameters, such as varying total flow rate of gas inlet, chamber pressure, growth temperature, wafer carrier rotation, it has been finally obtained the favorable conditions of the better uniform distributions of steady flow and thermal field profiles for growing high quality compound semiconductor materials inside the reactor. Then, the long- wavelength metamorphic In_0.53Ga_0.47As PIN photodetectors grown on semi-insulating GaAs substrates are successfully demonstrated by low temperature InP buffer technology. The active area of this photodetector is 50μm×50μm and the thickness of In_0.53Ga_0.47As adsorption layer is 300 nm. The 3dB bandwidth of frequency response reaches 6GHz. The responsivity of 0.12 A/W to 1550 nm optical radiation, corresponding to the external quantum efficiency of 9.6%, was achieved.

Novel schemes of optical power equalizer (OPE) and optical hard limiter (OHL) are presented, which base on quantum-dot semiconductor optical amplifiers (QD-SOAs) and adopt a traveling-wave QD-SOA in each arm of Mach-Zehnder interferometer (MZI). The function of power equalization and hard limitation can be realized respectively in a wide range by setting the phase difference between two arms of Mach-Zehnder interferometer.

Effect of Al-N codoping ratio on the conducting and optical properties of ZnO films deposited by helicon wave plasma assisted radio frequency magnetron sputtering under various N₂ gas flow is investigated. Hall measurements show that p-type ZnO thin films have been achieved with proper N₂ flow rate. X-ray diffraction patterns indicate that all the films are highly c-axis oriented. Room temperature photoluminescence spectra show a strong near-band-edge emission. With increasing N doping, the intensity of the emission behaves an increased and then decreased trend while the full width at half maximum is narrowed and then widened. In addition, photoluminescence spectrum at 77 K in the p-type ZnO film with the highest hole concentration show a much stronger peak near 3.32 eV (due to N related neutral acceptor bound excitons), than at 3.36 eV (neutral donor bound excitons), and the acceptor energy level is estimated to be 186 meV.

UV photocuring technology has encountered increased applications in recent years, which finds a variety of applications on protective coating of the optical-fiber, ink and optical recording materials. Combined with techniques of photohardenable, microcapsule, heat-sensitive and interface-polymerization method, a novel photoheat sensitive recording material of non-silver salt is explored in this thesis. Microcapsules are particulate substance with a core and shell structure, where photopolymerizable composition, monofunctional/polyfunctional diluents, photopolymerization initiator, photosensitivity enhancing agent and dye precursor are encapsulated as the internal phase. In this paper introduced the characteristics and curing mechanism of photo-sensitive microcapsule materials. The photocuring process may be a complex-function with photopolymerizable compound and photopolymerization initiator. For the sake of high photocuring speed and degree, optimal photo-sensitive materials were selected. In order to match with the light source excitation wavelength and absorb more wider ultraviolet band, combined type of photo-polymerization initiators were employed. With the kinds and dosage of photopolymerization initiator changing, the photocuring speed and quality can be ameliorated. Through studying the UV-visible absorption spectrum and infra-red spectrum of the material , the optical response property of the inner compound can be obtained.

Finite-Difference Beam Propagation Method (FD-BPM) in conventional is modified, according to more accurate Helmholtz equation, a new arithmetic is advanced. By using the new arithmetic and the old arithmetic in calculating slab waveguide and calculate the parameter which scales the precision of the method and the calculating time, we prove that the accuracy of the new arithmetic is improved without affecting time performance. At last we calculate the transmission mode in the AWG by the new method to show the practical value of the modified arithmetic.

Experiments of a lateral semi-insulating GaAs photoconductive semiconductor switch triggered by nanosecond serial laser pulses were reported. The switches were insulated by solid multi-layer transparent dielectrics. Jitter-free electrical pulses with steady voltage amplitude from the 0.5 mm-gap GaAs switches were observed. Its change of amplitude was less than 1.1%, the triggered jitter-time was less than 10ps, and pulse width was up to sub-nanosecond. The Jitter-free and steady speciality of electrical pulses from the photoconductive semiconductor switch was analyzed. It was indicated that ultra-fast electrical pulse with steady voltage amplitude and pico-second triggered jitter-time can be obtained by controlling switch trigger condition and optimizing switch design.

Microchip-laser-pumped supercontinuum (SC) is successfully generated through a 30-m long photonic crystal fiber (PCF). The spectra bandwidth of SC is 850 nm spanning from 550 nm to 1300 nm. The -15dB-flat bandwidth is 400 nm spanning from 600 nm to 1000 nm. It is easy to achieve a much more flat SC with the sacrifice of spectra bandwidth. A detailed simulation is carried out to help us understand more about the supercontinuum generation process. The primary mechanism of spectral broadening is identified as parametric four-wave mixing (FWM) combined with stimulated Raman scattering (SRS). These findings also demonstrate an effective way to generate a flat supercontinuum laser source.

In order to clarify the relationship between the water resistance and compositional additives in the primary coating for optical fibers, we prepared various primary coatings that contained silane coupling agents in combination with amine synergists. We observed the appearance of the interface between glass and primary coating after soaking in water at 65° for 30 days. Water resistance was found to be heavily influenced by the content and type of silane coupling agents and amine synergists and their trends are reported.

A series of novel fluorinated polyimides second-order nonlinear optical (NLO) materials were synthesized from poly(hydroxy-imide)s, followed by the Mitsunobu reaction with NLO thiazolylazo chromophores. The polyimides prepared were characterized by IR, UV-vis, gel permeation chromatography (GPC), thermogravimetric analysis (TGA), differential scanning calorimetric analysis (DSC) and X-ray diffraction (XRD). These NLO polyimides possess high glass transition temperature (T_g) in the range of 193-200 °C with thermal stability up to 288 °C. The electro-optic coefficients (r₃₃) at the wavelength of 1550nm for polymer thin films poled were measured by the attenuated total reflection (ATR) method. The r₃₃ values of the polyimides 1a and 2a containing thiazolylazoaniline chromophore are better than that of the polyimides 1b and 2b attached thiazolylazopyrimidine chromophore, due to the thiazolylazoaniline chromophore having large hyperpolarizability in contrast to the thiazolylazopyrimidine chromophore. Low optical losses (1.8-2.1 dB/cm at 1.55 μm), which were measured via an immersion technique have been observed for these polymers. The polyimides demonstrate an excellent combination of thermal stability, electrooptic (EO) coefficients and optical loss, and therefore they are suitable for EO applications.

A passively Q-switched pulse-LDA (laser diode array)-pumped Nd:YVO₄ laser using As⁺ implanted GaAs as the saturable absorber is demonstrated. In the experiment, a Q-switching pulse width 7ns with a pulse energy 23.5μJ is achieved which, to our knowledge, is the shortest pulse width in a passively Q-switched Nd:YVO₄ laser using GaAs as saturable absorber. The laser emits only one Q-switching pulse during each pump-pulse time with a Q-switching efficiency of 26.8%. We also investigate the characteristics of the Q-switched pulse by adjusting the pumping pulse energy, pulse width and pulse repetition rate respectively. The experimental results are discussed as well in the paper.

The Si-rich SiNx:H films have been prepared by helicon wave plasma-enhanced chemical vapor deposition (HWP-CVD) technique. Parts of the samples have been post-annealed at 800 °C in the H₂, FG (10%H₂ in N₂), and N₂ ambient, respectively. Fourier transform infrared spectroscopy (FTIR) and the optical absorption spectroscopy have been used to investigate the influence of different annealing environment on the structural and optical properties of the films. After the thermal annealing process, there is a significant increase of Si-N bonding density. Meanwhile, the band related to hydrogen (N-H and Si-H) decreased which indicates that the hydrogen is effused out of the films during the annealing treatment. The Si-sH stretching vibrations can be divided into three components by Gaussian distribution; the Si-H absorption band at different wave numbers corresponds to different configurations. The changes of the three peaks contributions decreased indicate that the configurations of the Si-H stretching vibrations band occurs restructuring in the different annealing environments. Furthermore, the investigation of the optical absorption spectroscopy suggests that the band gap E_g decreased after the thermal annealing process. The decreased optical gap should be related to the loss of hydrogen and the slightly increase in the mean size of silicon nanoparticles, which is in good agreement with that of the hydrogen bonding structure.

All-optical logic gate based on photonic crystal waveguides is a promising technique in future high-speed all-optical signal processing. In this paper, we propose a XOR logic gate based on two dimensional triangular lattice photonic crystals composed of cylindrical silicon rods in air. The main structure of the device is a line defect asymmetric Y branch waveguide. It is expected that there should be a phase shift between the two input beams. Hence, if an appropriate initial phase is introduced, the two input beams may interfere constructively or destructively to realize the logical functions. The simulation results show that the proposed all-optical photonic crystal waveguide structure could really function as XOR logic gates. The interference section length and width of photonic crystal waveguide structure are optimized for achieving the optimal performance for the proposed XOR logic gates. This device is potentially applicable for photonic integrated circuits.

Dual microring resonator array coupled via 3×3 couplers are studied using matrix formalisms. Transmission spectra are investigated as functions of column numbers and coupling coefficients in detail. Multiple transparent peaks appear when the column number increases for arrays of the first two types. The spectra for arrays of the other two types show complicated characteristics as functions of coupling coefficients.

Protocrystalline silicon/amorphous SiC multilayer films were fabricated by helicon wave plasma enhanced chemical vapour deposition (HW-PECVD). Atom force microscopy, Raman scattering and optical absorption measurements were used to analyze the microstructure and optical properties of the multilayer films. Experiment analyses reveal that through inserting transient a-SiC layer into film depositing process, well-controlled pc-Si:H films have been obtained in the growth condition of the μc-Si:H. The optical gap is observed being tuned from 2.15 to 2.43 eV by varying single pc-Si:H layer thickness. Such multilayer structure should have potential application in constructing high efficiency and stable Si-based solar cells.

High power laser diode array with an emission wavelength of 1064nm is presented. The epitaxial structure is an InGaAs/GaAsP strained-compensated single-quantum well structure. The modules CW output power can reach to 56.5W at current of 80A. Because the heat capacity of st rather shorter pulse duration and lower duty cycle, the average driving power in the laser chip is quite low, so the heating effect cemiconductor laser is very small, using pulse injection can reduce temperature rising significantly. Aould be neglected. The definite relation between lasing wavelength and chip temperature is developed. The temperature drift coefficient is 0. 45nm/ K

Temperature characteristics of several familiar high power diode lasers with broad area, whose wavelength was separately 808 nm, 810 nm, 940 nm and 980 nm, were analyzed. In order to see the effect the change of the quantum well structure on the characteristic temperatures, different structures were attempted. For the 808 nm structure, we tried different barrier thicknesses. For the 810 nm structure, different cavity lengths were attempted. And we studied the 940 nm and 980 nm also. In this paper, the widths of these devices were all 100 μm. Characteristic temperatures of these devices were calculated. The appropriate structure was available for different application.

High quality crack-free GaN layers were successfully grown and the InGaN/GaN based blue LEDs fabricated on patterned Si (111) substrates. In addition to using the patterned growth technique, thin AlN and SiNx interlayers grown at high temperatures were also employed to partially release the residual stress and to further improve the crystalline quality. 300 µm square blue LEDs fabricated on the islands, without thinning and package, exhibited a high output power of around 0.68 mW at a drive current of 20 mA.

Firstly, the vertical external-cavity surface-emiting lasers (VECSELs) device structure and model was given, and the output characteristic was simple calculated. Then, in experiment, the VECSELs were grown, bonded on to the heat sink, and optically pumped by high-power 808nm diode laser array with fiber output module, the light emission spectra were measured. Finally, The thermal characteristic of the VECSELs was investigated by changing the temperature of the substrate.

A systematic investigation about the strain distributions around the InAs/GaAs quantum dots using the finite element method is presented. A special attention is paid to the influence of InGaAs strain reducing layer. The numerical results show that the horizontal, vertical strains components and the biaxial strain are reinforced in the InAs quantum dot due to the strain-reducing layer. But the hydrostatic strain in the quantum dot is reduced. In the framework of eight-band k • p theory, we studied the band edge modifications due to the presence of strain reducing layer. Results demonstrate that, the strain reducing layer yield the decreasing of band gap, i.e., the redshift phenomenon observed in experiments. Our calculated results show that the degree of the redshift will increase with increasing of the thickness of strain-reducing layer. In calculating the influence of SRL, we discussed two circumistances: the height of the strain reducing layer larger and smaller than that of QD. The composition of the strain reducing layer on the degree of redshif is also investigated. The calculated results can explain the experiment results in literatures, and further confirmed that the long wavelength emission used for optical fiber communications is realizable by adjusting the dependent parameters.

A novel high-speed optical switch based on organic coumarin waveguide is presented. The device principle is based on influencing the bend loss in a waveguide by changing the refractive index contrast defining the guide. A low power femtosecond laser is used to excite the cladding of the curved waveguide. The beam propagation method is employed in the numerical simulation. The designed optical switch has a large extinction ratio and rapid response time (about 1.2ps).

A method of synthesis of silver sols is introduced and characterized, which is easily made, reproducible and convenient to combine with optical fiber. In a series of experiments, the hot spots in the mixture of silver sols just prepared and R6G should be chosen to get the high signal-to-noise Raman spectra (RS) of analyte molecule. Surface-enhancement Raman spectrums (SERS) of R6G are obtained in the form of thin film and liquid drop.

The luminescence decay curve from transitions of ⁴I _13/2->⁴I_15/2 in the Er3+/Yb³⁺-codoped PLZT transparent ceramic was measured. A model for the dynamics of frequency upconversion in Er³⁺/Yb³⁺-codoped PLZT transparent ceramic based on the rate equations was proposed. The dynamics of the upconverted emissions were studied to evaluate energy transfer rates between Er³⁺ and Yb³⁺ ions, and the forward energy transfer rate for Yb³⁺ to Er³⁺ and the backward transfer rate for Er³⁺ to Yb³⁺ were 7.19x10^-17 cm³s-1 and 3.73×10^-17 cm³s^-1, respectively.

Photoconductive antenna as continuous-wave terahertz photomixer has attracted much attention in these years. Its main restriction is the limited terahertz radiant power. In this paper, terahertz emission from dipole photoconductive antenna structures based on the photomixing mechanism has been studied. The terahertz output power is proportional to the radiation resistance of the antenna, the square of dc conductance and that of bias voltage. The photoconductive antenna radiation impedance as a function of frequency has been calculated numerically. And results reveal that the dipole photoconductive antenna design dominates the properties of the radiated output at resonant frequencies below 1THz, while the efficiency at higher frequencies is additionally dependent on the design of the interdigitated fingers, the effect of which is modeled by a lumped capacitance in parallel with the photoconductive area.

All-optical wavelength conversion of differential phase-shift keyed (DPSK) signals based on SOA in a Mach-Zehnder interferometer (SOA-MZI) configuration is simulated and analyzed using the transfer function of MZI and a wideband dynamic model of SOA. The operation principle is analyzed and operation point selection, influence of SOA physical parameters, different signal format and operation speed are discussed in detail. The results of 10Gb/s operation show that SOA-MZI is compatible with both non-return-to-zero (NRZ) and return-to-zero (RZ) formatted signals. However, the conversion performance is sensitive to the operation point of the involved SOAs. To maximize the Q value of the demodulated conversion signal, the power and wavelength of the original DPSK signal and the probe light should be optimized to obtain approximately π phase difference between the upper and lower arms of MZI in the middle of each bit. Besides, SOA with short carrier lifetime and large linewidth enhancement factor is preferred for wavelength conversion applications. 40Gb/s operation is also simulated with SOA carrier lifetime of 100ps, and the results strongly suggests 40Gb/s operation with RZ formatted signals and relatively large input powers of the clock signal.

We report the photoluminescence enhancement of nc-SiC films by coating nanostructure Ag films and study the influences of surface plasmon on photoluminescence properties by varying spacer thickness. PL curves of the samples deposited with different thickness of α-SiNx present two PL peaks which are contributed to the interference in the films and surface plasmon resonance, respectively. The PL intensity of the sample coated with Ag film is quenched due to combination of Forster nonradiative process and coherent photonic mode reduction in nc-SiC films, while the PL intensity of the samples with inserted spacer α-SiNx is enhanced because of the surface plasmon resonance.