High-speed silicon electrooptic Modulator design

An electrically driven Mach-Zehnder waveguide modulator based on high-index contrast silicon split-ridge waveguide technology and electronic carrier injection is proposed. The excellent optical and carrier confinement possible in high-index contrast waveguide devices, together with good thermal heat sinking and forward biased operation, enables high-speed modulation with small signal modulation bandwidths beyond 20 GHz, a V/sub /spl pi// times length figure of merit of V/sub /spl pi//L=0.5 V/spl middot/cm and an insertion loss of about 4 dB. The modulator can be fabricated in a complementary metal-oxide-semiconductor compatible way.     

Active mode locking of lasers using an electrooptic deflector

The deflector shows excellent loss modulation characteristics in a laser cavity under large signal operation. The mode locker is capable of generating very short optical pulses comparable to those obtained by passive mode locking. In experiments, an LiTaO₃ double-prism deflector is used as the mode locker for an Nd:glass laser. As a result, stable 6-ps pulses are obtained     

High-speed modulation of an electrooptic directional coupler

A LiNbO3:Ti directional coupler driven by an RF signal has been tested at 1.06 μm over a large modulation bandwidth. An analytical model has been developed leading to simple usable expressions to describe the theoretical dependence of the frequency spectrum of sinusoidally modulated light. The frequency response has been measured with a scanning Fabry-Perot and also with a high-speed photodiode. Both methods provided results which are in good agreement. The 9 mm long switch exhibited a 2.5 GHz bandwidth; a 16 dB extinction ratio has been achieved with a driving power of approximately 50μW/MHz. The confirmation of practical modulation response expressions shows the advantage of the optical spectrum observation, which is a very simple measurement method without any bandwidth limitation. In addition, this method has the advantage of remaining quite accurate even for large modulation signals.     

Generation of arbitrarily shaped optical pulses in the subnanosecond to picosecond region using a fast electrooptic deflector

New types of optical-pulse shaper and compressor in the subnanosecond to picosecond region are proposed, in which a fast electrooptic deflector is used together with Fourier optical elements (e.g., spatial fdter, lens, slit, grating, etc.). In the preliminary experiment using a LiTaO3electrooptic-deflector device and a CW 633 nm HeNe laser, various types of shaped pulse, for example, Gaussian, squared, triangle, and double-peak pulses, were obtained with 94 ps minimum duration.     

High-speed electrooptic modulation in GaAs/GaAlAs waveguide devices

A figure of merit is constructed for broad-band electrooptic modulators which compares bandwidth with launched generator voltage standardized to a common wavelength. Comparison of various published results in terms of this figure shows that a lumped-element III-V semiconductor device performance may be no more than a factor of two below that of typical (i.e., LiNbO3) traveling wave devices and are probably easier to implement-especially in an integrated format. Accurate modeling, which incorporates all transit time and velocity match effects, is described and found to agree well with experimental results. Experimental GaAs/GaAlAs modulators have been made, using a Mach-Zehnder interferometer configuration. At a wavelength of 1.15 μm and with unterminated drive a bandwidth of 6.5 GHz was obtained with Vpiof 17.3 V. A shorter (34.6-v) device was ∼ 1.25-dB down at 8.4 GHz. The corresponding figures of merit are close to the maximum expected for the configurations used.     

High-speed electrooptic phase modulators using InGaAs/InAlAsmultiple quantum well waveguides

High-speed phase modulation of waveguided InGaAs/InAlAs multiple-quantum-well optical modulators operating at 1.55 μm is described. The modulator requires a low voltage for π-phase-shift ( V_π=2.5 V) as well as a small intensity modulation depth of 1 dB. The measured electrical 3-dB bandwidth is 10 GHz, giving a bandwidth-to-voltage ratio of 4 GHz/V     

High-speed m sequence generation

A method is described that enables maximal-length sequences to be generated over limited ranges of clock rates, at speeds in excess of those normally obtained. The technique uses an analogue delay line to compensate for the delay inherent in the feedback network used in m sequence shift-register generators.     

Optical regenerative oscillation and monostable pulse generation in electrooptic bistable devices

Optical regenerative oscillation is discussed theoretically and experimentally in three types of mirrorless bistable optical devices based on the electrooptic light modulator. The devices have two feedback signals proportional to the optical output power, and the oscillation condition and oscillation frequency depend on the time constants and conversion factors for two feedback voltages and biasing phase retardation in the light modulator. Analysis is done by treating the coupled differential equations for the time dependent feedback signals. The experimental results agree with the theoretical prediction. We show also that optical monostable pulses can be generated in the three types of bistable optical devices.     

A novel net-degree distribution model and its application to floorplanning benchmark generation

This paper characterizes the behaviour of multi-terminal nets in a circuit to provide an accurate estimation of interconnect net-degree distribution. Based on Rent's rule, we derived a new net-degree distribution model, called the weighted exponential model. Numerical evaluations show that weighted exponential model is more accurate than any other currently available net-degree distribution models. It generates from 18% to 87% smaller average absolute errors in the prediction of the total number of nets and average net degree. Moreover, it was observed that the internal fraction factor f, that represents the ratio of the number of new internal nets to the total number of new nets, similarly to Rent's rule, exhibits Regions II and III. With a refined value of f, our model can provide even more accurate estimation of net-degree distribution.

A method to generate floorplanning benchmarks using weighted exponential model is presented. Thanks to the accuracy of new model and the introduction of a block-degree distribution, the significantly improved benchmark generator, BGen, outperforms a prototype tool we have previously developed using Zarkesh-Ha et al's model.     

High-speed generation of long m-sequences

A method was recently described by Arvillias and Maritsas for high-speed generation of m-sequences having characteristic polynomials of the form 1 ? xq ? xp. Here the method is extended to generate m-sequences with characteristic polynomials having more than three terms.     

Properties of avalanche injection and its application to fast pulse generation and switching

The positive- and negative-resistance characteristics of the avalanche-injection diode are derived from a set of fundamental equations. The field dependence of the ionization rate-constant, the resistivity of the avalanching region, and the injected current are taken into account to compute the final voltage-current characteristics. From these characteristics, the transient electrical time constant for switching is estimated. The discussions of the injection-stimulated avalanche are extended to a transistor for pulse generation at a high repetition rate. Sharp pulses as fast as 500 MHz have been observed with this "injection-controlled avalanche thyristor." The device is suitable for pulse amplification. Also realized are negative resistances in both emitter and collector characteristics, which also operate very rapidly. Discussions are speculatively extended to the possibility of a repetition rate as high as 1000 MHz.     

高速AD7654转换器及其在存储测试系统中的应用

为了研制应用于跌落试验等环境试验的存储测试系统,利用高速A/D转换芯片AD7654结合SoC片上系统C8051F340逻辑时序控制的方法来实现200KSPS采样速率的系统指标要求。AD7654是AD公司推出的一款低功耗、四通道、电荷再分布式、16位500KSPS高速A/D转换器。在此介绍了AD7654的主要特点、工作原理和逻辑时序,并为了实现并行存储测试的实际需要,设计了AD7654与SoC片上系统以及非易失性存储器的接口电路,并给出相应了相应的A/D中断服务程序。该提供的方法对类似的项目有一定参考价值。     

Optical pulse generation using guided-wave electrooptic modulator with resonant electrodes and polarization reversal

This paper reports on optical pulse generation using a new guided-wave electrooptic (EO) phase modulator with long resonant electrodes and polarization reversal. Adopting polarization-reversal structure to a guided-wave EO modulator with long standing-wave resonant electrodes, high-efficiency optical modulation is obtained by the compensation of the transit-time effect. By operating a fabricated EO phase modulator with a large amplitude modulation signal, optical sidebands over 100 GHz were obtained. Furthermore, optical pulse trains of an /spl sim/ 25-ps pulsewidth and a 15.28-GHz repetition frequency were successfully obtained by controlling the generated optical sidebands by use of an optical synthesizer.     

High-speed CdS0.2Se0.8photoconductor and its application to line-image sensors

The photoelectric properties of CdS1-xSex(x = 0.4-1.0) photoconductor-type sensors were measured. The sensors were made by heat-treating an evaporated film under the influence of CdCl2vapor. The photocurrent Jpis large, and the dark current Jdis small; theS/Nratio derived from theJ_{p}/J_{d}ratio reaches a value of more than 60 dB. With increasingx, the decay time of the photocurrent decreases, while the rise time increases. By addition of continuous light bias, the rise time is drastically reduced. Furthermore, the decay time is reduced by increasing the applied voltage. These effects are pronounced for a CdS0.2Se0.8sensor. Using this sensor, we constructed a contact-type line-image sensor (8 bits/mm, 1728 bits), and attained a scanning rate of 1 ms/line and a total time of about 2 s for reading an ISO A4 size document. The reading was performed under an application of 20 V, and an illumination of 7.5-µW/cm²light bias and 15 µW/cm²(∼100 lux) signal light using LED light sources (570 nm).     

高速三维测量系统及其在水晶内雕中的应用

提出了一种采用DMD的高速三维测量系统,实现三维实物的高速、高分辨率扫描,降低了对被测对象的运动状态要求。然后利用Ball-pivoting算法实现三维表面重构,最后将利用激光内雕机实现水晶内雕三维输出。实验中高速三维测量系统的测量速度达到90fps,成功实现了人脸三维数据的采集及水晶内雕成品制作。高速三维扫描系统为动态真实物体个性化水晶内雕的推广普及提供了有效的技术手段。     

An extension of the differential image foresting transform and its application to superpixel generation

The Image Foresting Transform (IFT) is a graph-based framework to develop image operators based on optimum connectivity between a root set and the remaining nodes, according to a given path-cost function. Its applications involve a variety of tasks, such as segmentation, boundary tracking, skeletonization, filtering, among others. The Differential Image Foresting Transform (DIFT) allows multiple IFT executions for different root sets and a same monotonically incremental path-cost function, making the processing time proportional to the number of modified nodes. In this paper, we extend the DIFT algorithm for non-monotonically incremental functions with root-based increases. This proposed extension, called Generalized DIFT (GDIFT), has been successfully used as the core part of some modern superpixels methods with state-of-the-art results. Experimental results show considerable efficiency gains over the sequential flow of IFTs for the generation of superpixels, also avoiding inconsistencies in image segmentation, which could occur with the regular DIFT algorithm.     

High-speed InGaAlAs/InAlAs multiple quantum well electrooptic phasemodulators with bandwidth in excess of 20 GHz

High-speed phase modulation (in the frequency bandwidth of 20 GHz, the highest yet reported for multiple quantum well (MQW) phase modulators) for waveguided InGaAlAs/InAlAs MQW optical modulators is reported. The modulator successfully operates at a long wavelength of 1-55 μm with a low required voltage for phase shift (Vπ=3.8 V), small intensity modulation depth below 1.5 dB, and without any modulation bandwidth degradation up to 20 GHz under high input optical power of 0 dBm in single-mode fiber     

特定人脸的3D模型生成与应用的研究

计算机3D人脸对象的应用范围十分广泛,包括虚拟现实、辅助教学、远程会议、人机交互、游戏娱乐、电影制作等诸多方面。提出了利用区域差值法的算法实现基于两幅人脸图像生成具有特定人特征的3D人脸模型,并在生成的特定人3D人脸模型的基础上实现了基于MPEG 4的特定人的人脸动画功能,实验取得了良好的效果。     

0 to 3 GHz traveling-wave electrooptic modulator

A report is given on the construction and testing of a traveling-wave electrooptic modulator that requires a nominal 5-watt drive power to obtain 30 percent amplitude modulation from 0 to 3-GHz. The modulator employs potassium-dihydrogen-arsenate crystals and has been tested at 6328 Å with CW drive power.