A novel OCDMA drop unit based on fiber gratings and 2D wavelength-time codes

A novel drop unit for the optical code-division multiple access(OCDMA) based on fiber Bragg gratings and two-dimensional wavelength-time code is studied.The simple OCDMA drop unit can drop a code channel without disturbing the rest code channels.A similar unit for dropping a group of code channels is also proposed.Numerical simulation is given.The system delay can decrease by substituting the electrieal driving optical switch with a specific optical driving.The single channel drop unit can also be the basis for multiple channels drop.

Optical and Electrical Properties of Sensitized Polyaniline by Electrochemical Polymerization

To sensitize polyaniline with dyes by electrochemical polymerization, HClO 4 is employed as the dopant and oxidant, and the polyaniline with different sensitive properties is synthesized. The effect of sensitized emeraldine salt on the absorption spectrum is discussed in details. The maximum conductivity of sensitized films reaches 1.22 S/cm, and investigation on dye sensitizing of the polymer reveals that C.I. Direct Blue 71, C.I. Direct Blue 84, C.I. Direct Black 19 and CuPc-(COOH) 4 may enhance the photoconductivity of polyaniline greatly.

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 noise ,low drift operational amplifiers,6-pole Butterworth filters and perfect digital signal processing circuits.

QUANTUM COLLISION SEARCH ALGORITHM AGAINST NEW FORK-256

In order to improve the attack efficiency of the New FORK-256 function, an algorithm based on Grover's quantum search algorithm and birthday attack is proposed. In this algorithm, finding a collision for arbitrary hash function only needs O(2m/3) expected evaluations, where m is the size of hash space value. It is proved that the algorithm can obviously improve the attack efficiency for only needing O(2 74.7) expected evaluations, and this is more efficient than any known classical algorithm, and the consumed space of the algorithm equals the evaluation.

Kravchenko probabilityweight functions in problems of radar signals correlation processing

In this report the combined method of correlation radar signal(RS)processing based on the theory of atomic functions(AF)is examined.Examples of using of new Kravchenko probability weight functions(WF)designs are presented.Quality functional to estimate accuracy and efficiency of RS processing for concrete physical models is constructed.It is shown that the proposed approach significantly improves the quality of the coherent analysis of RS.

Comparison of Ge_xSi_(1- x) Grown by UHV/CVD from Si_2H_6/GeH_4 and SiH_4/GeH_4

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.

Influence on Conductivity of Polyparaphenylene by Chemical Doping and Ion Implantation

Polyparaphenylene(PPP) is prepared by AlCl 3-CuCl 2 catalysts with benzene as the monomer and is doped by chemical method and N + ion implantation. The influences of the concentration, temperature and time of chemical doping and the dose, energy and temperature of ion implantation, on PPP conductivity are investigated. The results showed that the conductivity of PPP can be improved 4～5 orders of magnitude by ion implantation and the conductivity of PPP can reach about 0.11 S·cm -1 by chemical doping. The comparison of stability of the material conductive behavior by using the two doping methods is presented. It shows that ion implantation is better than chemical doping in stabilizing the electric conductive behavior for the material.

MOTION COMPENSATION USING SUBSTRIP PGA

MOtion COmpensation(MOCO) is an essential step in high resolution airborne Synthetic Aperture Radar(SAR) imaging. Generally, a reference altitude level is assumed and external Digital Elevation Model(DEM) is required for the scene topography heavily varied. To overcome the shortcoming, we propose a MOCO method based on Phase Gradient Autofocus(PGA) which can obtain well focused images without DEM. In the implementation, we first compensate the normal range-invariant term. Then the data are divided into strips in range-compressed domain and PGA is applied to each substrip to extract the phase errors. Finally, the phase error surface is obtained using interpolation and then compensated. Real airborne SAR data of a UAV-SAR system experiments and comparisons demonstrate the validity and effectiveness of the proposed algorithm. The results show that our algorithm is effective.

Photoelectric Property of Polyaniline Doped with Organic Sulphonic Acid

Photoelectric property of polyaniline doped with dodecyl-benzene sulphonic acid (DBSA) is studied. The result shows that the concentration of carrier increases obviously, when polyaniline doped with DBSA is irradiated with light. Mixture of sensitive material is advantageous to the absorption of polyaniline in visible light spectrum, and the conductivity is also improved. The results of dielectric measurements on polyaniline doped with DBSA in an Al-PAn-DBSA-Al configuration as function of frequency and temperature are reported. The space-charge polarization phenomenon is observed. Carrier lifetime is microsecond magnitude and mobility is (0.001～0.1) cm 2/V·s, which are obtained by calculation or experiment. The active energy is obtained from the relation between conductivity and temperature. The conducting mechanism of PAn-DBSA is analyzed.

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 centers conditions are simulated by means of Monte Carlo method. The quantitative results about the influence of charged centers on electron energy are obtained.

Low Distortion 1.31μm AlGaInAs/InP MQW DFB Laser Module for CATV Systems

A high power and low distortion 1.31 μm AlGaInAs/InP multiquantum well distributed feedback laser diode (MQW DFB LD) with RWG structure has been developed by MOCVD technique. The fiber output power of butterfly packaged module with optic isolator P f is more than 10 mW, threshold current is in the range of (13～20) mA, slope efficiency, E s>0.30 W/A and side mode suppression ratio, R S,M,S >35 dB. The composite second order, O C,S <-61 dBc and composite triple beat, B C,T <-65 dBc are obtained by test frequencies of (45～550) MHz with 60 PAL channels. In the test conditions the carrier to noise ratio, R C,N >51 dB.

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 rare 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 Φ 5 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.

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.

Effects of Substrate Pretreatment Conditions on Quality of GaN Epilayer

The pure cubic GaN(c-GaN) has been grown on (001)GaAs substrates by ECR-PAMOCVD technique at low temperature using TMGa and high pure N2 as Ga and N sources, respectively. The effects of substrate pretreatment conditions on quality of cubic GaN epilayer are investigated by the measurements of TEM and XRD.It is found that hydrogen plasma cleaning, nitridation and buffer layer growth are very important for quality of cubic GaN epilayer.

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 10 nm/min. The atomic composition ratio, N/Si, which is evaluated by Rutherfold backscattering method is about 1.4 under a given experimental conditions more than the stoichiometric value of 1.33 in Si 3N 4. The infrared transmission spectra show a large dip at 850 cm -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 resistivity and the breakdown electric field are presented.

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.

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

The wavelength tuning ranges of a grating external-cavity laser diode (ECLD) have been studied by the equivalent cavity method. The maximum tuning range (MTR) and the continuous tuning 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 MTR. 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 internal-cavity reflectivities to obtain a given CTR in the design of an ECLD.

Electro-optical Properties of Liquid Crystal Composite Materials

The liquid crystal composite materials consist of microdroplets of liquid crystals which are spontaneously formed in a matrix of a polymer at the time of its polymerization. The director configuration in liquid crystal droplets, the model of orientation of droplets, and the contrast ratios of a cell are investigated. Droplet size, spacing and distribution are readily controlled in these materials to allow optimization of displays based upon electrically controlled light scattering from the liquid crystal droplets. Preliminary experimental and theoretical studies of the light scattering and electro-optic response of new material show that these materials can offer new features suitable for large area displays and light valves.

New Fluoroptic Therm ometer with Optical Fiber

A new optical fiber fluoroptic thermometer based on the temperature—fluoroptic characteristic of fluoroptic materials is presented.The ratio technique of intensities of fluorescent emission lines of certain rare earth phosphors is used,making the measurement of temperatures of the system to 0.5 ℃ precision. The characteristics of thermometer are discussed and the experiment results of temperature are given.

Resolution Characteristics of GaAs/GaAlAs Transmission Photocathode

The resolution characteristic of GaAs/GaAlAs transmission 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.