Simulation and Fabrication of Sampled FIber Bragg Grating

The calculation principle of sampled FBG,which is called transfer matrix method, is analyzed and the simulation software is designed.The sampled FBG is simulated with the software we designed and is fabricated by ourselves.The experiment result fits well with the simulated one.It is concluded that to improve the refractive modulation index is an effective way to fabricate a sampled FBG with high-reflectivity.     

Irradiation Defects in Silicon Crystal

The application of irradiation in silicon crystal is introduced.The defects caused by irradiation are reviewed and some major ways of studying defects in irradiated silicon are summarized.Furthermore the problems in the investigation of irradiated silicon are discussed as well as its properties.     

Maximum and Continuous Wavelength Tuning Ranges of a Grating External—cavity Laser Diode

The wavelength tuning rages of a grating external-cavity laser diode(ECLD)have been studied by the equivalent avity method.The maximum tuning range(MTR)and the continuous tunding range(CTR),which are related to the maximum and the minimum threshold carrier densities,are deduced from the threshold condition.We define a ratio of the CTR to the MRT.This ratio is only determined by the reflectivities of the external and internal facets of the ECLD.The analysis shows that there is an appropriate combination of the external and internalcavity reflectivites to obtain a given CTR in the design of an ECLD.     

Surface Morphology and Photoluminescence of 1.3μm Wavelength In（Ga） As／GaAs Quantum Dots

Self-organized In0.5 Ga0.5As/GaAs quantum island structure emitting at 1.35 μm at room temperature has been successfully fabricated by molecular beam epitaxy(MBE) via cycled(InAs)1/(GaAs)1 monolayer deposition method.Photoluminescence(PL) measurement shows that very narrow PL linewidth of 19.2 meV at 300 K has been reached for the first time,indicating effective suppression of inhomogeneous broadening of optical emission from the In0.5Ga0.5As islands structure.Our results provide important information for optimizing the epitaxial structures of 1.3μm wavelength quantum dot （QD） devices.     

SiC衬底AlN缓冲层的应变对GaN外延层质量的影响

在3英寸(1英寸=2.54 cm)SiC衬底上采用金属有机物化学气相沉积(MOCVD)法生长GaN外延材料。研究了AlN缓冲层的应变状态对GaN外延层应变状态和质量的影响。使用原子力显微镜和高分辨率X射线双晶衍射仪观察样品表面形貌,表征外延材料质量的变化,使用高分辨喇曼光谱仪观察外延材料应力的变化,提出了基于外延生长的应变变化模型。实验表明,GaN外延层的张应变随着AlN缓冲层应变状态的由压变张逐渐减小,随着GaN张应力的逐渐减小,GaN位错密度也大大减少,表面形貌也逐渐变好。     

Elimination of Zig—zag Defects in Surface—stabilized Ferroelectric Liquid Crystal Cells

The elimination of zig-zag defects in polyimide-coated surface-stabilized ferroelectric liquied crystal(SSFLC)cells is carried out by appliying a low-frequency electric field.It has been achieved when the thickness of SSFLC cell is 3μm.The optical spectral transmittance measurement confirmed that there is no change of layer structure,and the memory capability was not improved.The different effects of low-frequency electric field applied on the different thickness FLC cells have been observed.and experimental results were presented.     

Comparison of GexSi1—x Grown by UHV／CVD from Si2H6／GeH4 and SiH4／GeH4

Using double crystal X-rays diffraction (DCXRD) and atomic force microscopy (AFM), the results of Ge x Si 1- x grown by UHV/CVD from Si 2H 6 and SiH 4 are analyzed and compared. Adsorbates can migrate to the energy-favoring position due to the slow growth rate from SiH 4. In this case, a Si buffer that isolates the effect of substrate on epilayer could not be grown, which results in a pit penetrating into epilayer and buffer. The FWHM is 0.055° in DCXRD from SiH 4. The presence of diffraction fringes is an indication of an excellent crystalline quality. The roughness of the surface is improved if grown by Si 2H 6; however, the crystal quality of the Ge x Si 1- x material became worse than that from SiH 4 due to much larger growth rate from Si 2H 6. The content of Ge is obtained from DCXRD, which indicates the growth rate from Si 2H 6 is largest, then GeH 4, and that from SiH 4 is least.     

Charged Centers in ZnS—type Thin Film Electroluminescent Devices

Charged centers exist in the phosphor layer of the common thin film electroluminescent devices.In this article,electron scattering process due to these centers is studied through phase shift analysis.The scattering rates in different cases are obtained and compared with other important scattering processes.Electron transport processed under different charged centrers conditions are simulated by means of Monte Carlo method.The quantitative results about the influence of charged centers on electron energy are obtained.     

Analysis of Optical Signal Transmission Characteristics in AWG Multi/Demultiplexer with Electromagnetic Field Theory

Based on the electromagnetic field theory, the optical signal transmission characteristics in input/output waveguides, slab waveguides and arrayed waveguides of the arrayed waveguide grating (AWG) multi/demultiplexer are analyzed. The relationship between the physical parameters such as geometry sizes and relative refractive index in AWG multi/demultiplexer and the optical signal transmission characteristics are discussed. This theoretical study can be used for optimizing the design and improving the performance of the AWG multi/demultiplexer.     

Enhanced Efficiency and Durability of Organic Electroluminescent Devices by Doping in Emitting Layer

Remarkable improvement in efficiency and stability has been observed in a doped organic electroluminescence device, which consists of a hole-transport layer, an electron-transport layer and a luminescent layer. The hole-transport layer is a N,N'-bis(3-methyphenyl)-N,N'-diphenylbenzidine film. The doped emitting layer consists of 8-(quinolinolate)-aluminum as the host and rubrene as the emission dopant. The doped device demonstrated a brightness in excess of 40 000 cd/m 2 and the maximum external quantum efficiency of 3.4%, which is about six times and four times respectively greater than those of the undoped device. For no packaged deviced, a luminance half-life on the order of about 230 h has been achieved under a constant current density of 15 mA/cm 2, starting at 500 cd/m 2 at the room temperature.     

A New Base—6 FFT Algorithm

A new FFT algorithm has been deduced, which is called the base-6 FFT algorithm. The amount for calculating the DFT of complex sequence of N =2 r by the base-6 FFT algorithm is M r( N )=14/3· N log 6 N -4 N +4 for multiplication operation of real number and A r( N )=23/3· N log 6 N -2 N +2 for addition operation of real number. The amount for calculating the DFT of real sequence is a half of it with the complex sequence.     

Optical Fiber Displacement Sensor with Ultra—high Resolution

A low fineness fiber optic Fabry-Perot interferometric displacement sensor has been developed and tested.A 0.005 nm displacement resolution is obtained by using He-Ne laser with a high performance,photodetectors with low nois,low drift operational amplifiers,6-pole Butterworth filters and perfect digital signal processing circuits.     

Temperature Dependence of Characteristics for Multimode Interference Based 3—dB Coupler in SOI

The temperature dependence of characteristics for multimode interference (MMI) based 3-dB coupler in silicon-on-insulator is analyzed, which originates from the relatively high thermo-optic coefficient of silicon.For restricted interference 3-dB MMI coupler,the output power uniformity is ideally 0 at room temperature and becomes 0.32 dB when temperature rises up to 550 K.For symmetric interference 3-dB MMI coupler,the power uniformity keeps ideally 0 due to its intrinsic symmetric interference mechanism.With the temperature rising,the excess loss of the both devices increases.The performance deterioration due to temperature variety is more obvious to restricted interference MMI3-dB coupler,comparing with that of symmetric interference MMI3-dB coupler.     

Influence on Conductivity of Polyparaphenylene by Chemical Doping and Ion Implantation

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Deposition of Silicon Nitride Films by Silane Hydrazine Process

A new catalytic chemical vapor process for depositing silicon nitride films using silane hydrazine gaseous mixture is described.This system can be useful at a temperature of lower than 400 ℃.The catalytic process gives more rapid deposition rate than 10nm/min.The atomic composition ration.N/Si,which is evaluated by Rutherfold backattering method is about 1.4under a given experimental conditions more than the stoiciometric value of 1.33 in Si3N4.The infrared transmission spectra show a large dip at 850cm^-1 due to Si-N bonds and no clear dip due to Si-O bonds.High N-H bond density is the evidence that the deposition mechanism is limited by N-N bond breaking of the hydrazine.The H contents,evaluated from Si-H and N-H bonds in the infrared absorption spectra,and the deposition rate are measured as a function of the substrate temperature.In addition some film properties such as the reistivity and the breakdown electric field are presented.     

Efficient Organic Multi—quantum Well Electroluminescent Devices Using Aluminum as Cathodes

Organic green light emitting devices(LEDs)with multi-quantum well(MQW)structure were fabricated.Aromatic diamine(TPD)was used as holetransporting layer and potential barrier layer;Tris(8-hydroxyquinoline)aluminunum(Alq3)was acted as electron-transporting emitter and MQW green emitter.Airstable aluinum(Al)was used as electron-injection contact.The influence of the thickness of potential barrier layer and the number of quantum well on the electroluminescent(EL)efficiencies of the devices was investigated.The organic LEDs with two quantum wells showed enhanced EL efficiencies.Maximum external quantum efficiency and brightness were 1.04% and 7000cd/m^2,respectively.     

Spectral Properties of Yellow Fluorescent Powder for White LEDs

Much attention has been paid to white LEDs because of their potential applications in the illumination.The doping of rate earth ions plays an important role in the optical properties of yellow fluorescent powder.And mainly aiming to raise the intensity and the luminous rate of the white LEDs and by photoluminescence and electroluminescence,the luminescence spectrum of yellow fluorescent powder bought from different places is measured.Furthermore,the luminous intensity in the normal direction and the angle distribution of half maximum power for the white LEDs packed with cylindrical φ5 epoxy on the same blue GaN chips are also measured under the same manufacture conditions.The results show that the yellow fluorescent powder bought from China mainland has higher optical output rate than that bought from China Taiwan and hence is more suitable to fabricate the white LEDs for practical use.     

Resolution Characteristics of GaAs/GaAlAs Transmission Photocathode

The reolution characteristic of GaAs/GaAlAs trransmission photocathode is an important parameter in third generation intensifiers.The modulation transfer function of GaAs/GaAlAs transmission photocathode is derived from a simple two-dimensional diffusion equation.The theoretical resolution characteristic of a 2 μm thick GaAs/GaAlAs transmission photocathode is calculated.The relationship between resolution and parameters in GaAs/GaAlAs transmission photocathode is discussed.A conclusion is shown that one can design the GaAs/GaAlAs transmission photocathode for maximum quantum efficiency,since the sacrifice in the resolution doesn‘t limit system performances.     

High Sensitivity FBG Pressure Sensor Based on Mechanical Amplifier and Interrogation Using Tunable FBG Filter

A high sensitivity fiber Bragg grating pressure sensor by using mechanical amplifier is demonstrated. The measured pressure sensitivity is -1.80×10 -4 /MPa, which is about two orders of magnitude better than a simple monomode fiber with an in-fiber grating. The resolution of pressure measurement is 0.015 MPa based on interrogation using tunable fiber grating filter.