Rigorous coupled wave analysis of induced photorefractive gratings

The usefulness of rigorous coupled wave theory in the analysis of induced transmission and reflection grating formation, wave mixing, and higher order generation is demonstrated. No approximations air made, exact photorefractive material equations are used, and optical and electrical anisotropies are included. Several new effects, such as time oscillation, higher order generation, etc., are predicted     

Converter circuit design, semiconductor device selection and analysis of parasitics for micropower electrostatic Generators

For various medical monitoring and sensing applications it is desirable to power the electronics by scavenging energy from any locally available source. An electrostatic motion-driven generator for low-frequency (human body) motion has been developed by the authors using microelectromechanical system technology. The prototype generates pulses of 250V on a 10-pF capacitor. This paper examines the design of a circuit and semiconductor devices to convert this energy to a low voltage. Because of the very small charge involved, the effects of leakage and parasitic stored charge are important. Converters for this application using silicon-on-insulator metal-oxide-semiconductor field-effect transistors and insulated gate bipolar transistors are compared using physics-based finite-element simulation. The overall effectiveness of the generation process is shown to be composed of several terms which are functions of system parameters such as generator flight time, semiconductor device area, and circuit inductance. It is shown that device area is a compromise between leakage current, charge storage, and on-state voltage. It can, for a given generator and inductance, be optimized to provide the maximum energy yield. Parasitic series inductance is shown to be of little importance to the circuit efficiency; however, parasitic capacitance has a significant influence.     

Rigorous numerical analysis of mode beating in tapered semiconductor amplifiers

The evolution of the optical beam profile along a high-power tapered semiconductor amplifier has been demonstrated by using rigorous and full-vectorial numerical approaches, based on the finite-element method. Numerically simulated results indicate the generation of many higher order modes, and their interference with the fundamental mode causes a variation of the optical beam, both along the transverse and the axial directions, which could significantly modify the output beam quality.     

顺电相KTN中反射型全息相位栅的衍射效率分析

在顺电相光折变晶体中存储全息相位光栅是研制新型电控全息光开关的有效途径。为了提高光栅的衍射效率,将Kogelnik耦合波理论与Kukhtarev方程相结合,得出了顺电相钽铌酸钾晶体中反射型相位栅衍射效率的解析式,对影响光栅衍射效率的各因素进行了计算分析。结果表明,使写入光的入射角远离45°、增加晶体厚度和增大外加电场等措施都可以使反射型全息相位栅的衍射效率提高。45°入射角附近出现较宽的低衍射区。衍射效率对入射角、晶体厚度以及外加电场的变化敏感,其中任一个参量的较小改变都可以引起衍射效率的较大变化。晶体的吸收对衍射效率的影响可以忽略。分析结果有助于在实践中调整参量以获得较高的读出光衍射效率。     

Polarization gratings: design and applications

Polarization gratings are nondepolarizing polarization elements that alter the polarization state of the transmitted light in a periodic way, yielding a polarization-dependent diffraction. Using both the Jones and Stokes formalisms, we demonstrate that the polarization states of the higher order waves do not depend on the polarization state of the incoming light and that they are fully characterized by the polarization grating vector. We furnish a general model for polarization gratings that can be advantageously used for their design and show that a chain of three polarization gratings is a achromatic in-line polarimeter. In addition, we show that polarization gratings can be used as a tool to measure polarization mode dispersion.     

多波长啁啾光纤光栅叠栅的数值分析和设计

为了研究多波长啁啾光纤光栅叠栅的反射和时延特性,提出多波长啁啾光纤光栅叠栅的耦合模理论方法,得到波长间隔Δλ=1.6nm的4波长和8波长的啁啾叠栅的反射谱和时延特性的数值分析结果,并设计了波长间隔Δλ=0.4nm的8波长的啁啾叠栅,数值分析结果与实验结果非常一致.结果表明,多波长啁啾光纤光栅叠栅的耦合模理论是可靠的,可用来分析其各种特性,此方法对多波长啁啾叠栅的设计和制作具有重要的参考价值.     

Demonstration, analysis, and device design considerations for independent DG MOSFETs

This paper describes a comprehensive study on the threshold voltage (V/sub th/) controllability of four-terminal-driven double-gate (DG) MOSFETs (4T-XMOSFETs) with independently switched DGs. Two types of 4T-XMOSFETs (fin and vertical) are experimentally demonstrated and their V/sub th/ controllability is thoroughly investigated in relation to the initial V/sub th/ in the DG-mode based on comprehensible modeling of the devices. Based on the investigation and simulated predictions, device design guidelines for 4T-XMOSFETs are proposed. Decreasing the workfunction of the DGs and increasing the oxide thickness of the second gate (T/sub ox2/) are preferable for improving the performance of the 4T-XMOSFET. The optimum workfunction of DGs for attaining low I/sub off(stand-by)/ and high I/sub on(active)/ under the limited V/sub g2/ condition is also proposed.     

Rigorous and approximate calculations of antireflection layer parameters for travelling-wave diode laser amplifiers

An integral equation method is used for an accurate numerical analysis of antireflection layers for travelling-wave diode laser amplifiers. Its results are compared with those of various approximate analyses; a new practical approximation is proposed.     

Modeling, analysis, and design of RF LDMOS devices usingharmonic-balance device simulation

This paper describes how device simulation may be used for the modeling, analysis, and design of radio-frequency (RF) laterally diffused metal-oxide-semiconductor (LDMOS) transistors. Improvements to device analysis needed to meet the requirements of RF devices are discussed. Key modeling regions of the LDMOS device are explored and important physical effects are characterized. The LDMOS model is compared to dc and small-signal ac measurements for calibration purposes. Using the calibrated model, large-signal accuracy is verified using harmonic distortion simulation, and intermodulation analysis. Predictive analysis and a study of the structure's parasitic components are also presented. Load-pull simulation is used to analyze matching network effects to determine the best choices for device impedance matching     

半导体器件的发展与固态纳米电子器件研究现状

简要回顾了半导体电子器件由真空电子管到固体晶体管,直至纳米电子器件的发展历程。分别比较了不同的半导体电子器件的材料、理论和所采用的制备技术。在此基础上综述了当前较热门的纳米电子学和固态纳米电子器件,并由纳米器件的分类简单介绍了当前固态纳米电子器件的三个部分,即量子点、谐振隧穿器件和单电子晶体管。最后对半导体器件的发展提出了展望。     

Diffraction of millimeter waves by projecting a shadow pattern onto a semiconductor

The transmission of millimeter waves through a semiconductor changes according to the amount of light falling on it. In the experiments reported here, a pattern of light and shadow is projected onto a sheet of semiconductor and the regions of greater and lesser transmission serve as a diffracting object for a millimeter-wave beam. The light source is a quartz tungsten halogen lamp. A lock-in amplifier is employed to overcome difficulties due to the differences in transmitted power being small.     

双向反射分布函数测量装置设计及指向精度分析

为实现对样品的双向反射分布函数（Bidirectional Reflectance Distribution Function,BRDF）的测量,设计了一种少光线遮拦、大回转半径和高定位精度的测量装置。根据测量空间和角度需要,设计了大回转半径（1.3 m）的方位圆环轨道和天顶弧形轨道。轨道外侧安装同步齿形带,采用伺服电机驱动带轮分别实现两个方向的运动。安装在天顶弧形轨道的探测器对位于装置中心的样品在方位角180,天顶角75范围内进行探测。为避免在大尺寸结构下的运动卡滞,设计了基于弹簧预紧的防卡死机构,并对机构引入的指向精度进行误差分析,最后对测量装置的指向精度进行了测量。实验结果表明:BRDF测量装置方位轨道指向精度优于0.147,天顶轨道指向精度优于0.358,测量结果与分析结果相符,验证了所设计的BRDF测量装置能够满足指标要求。     

An asymmetric discrete-time approach for the design and analysis ofperiodic waveguide gratings

A discrete-time approach is introduced for the analysis of periodic waveguide gratings with gain (or loss) extending concepts developed for transfer matrix and Gel'fand-Levitan-Marchenko (GLM) inverse scattering techniques. The periodic waveguide grating with gain (or loss) is modeled as a lossy layered dielectric that allows for a digital signal processing (DSP) formulation of the forward and inverse scattering problem. It is shown that the DSP forward scattering formulation as an asymmetric two-component wave system is equivalent to the impedance matching matrix method. A numerical example is presented to emphasize this result. The DSP formulation is an exact discrete design, not just an approximation to a continuous design, and includes all multiple reflections, transmission scattering losses, and absorption effects. A comparison of the continuous GLM, discrete GLM, and discrete Krein inverse problem formulations for a medium with gain (or loss) is presented. The discrete lossy formulations generalize previous lossless results and are found from two different types of reflection data. Since slab gratings are discrete (not continuous) structures, the integral equations used to describe the continuous inverse problem are shown to become matrix equations. Thus, our result enables fast algorithms to be used to solve the inverse problem. A fast algorithm is presented allowing for the complete reconstruction of the grating parameters from its two-sided response in a recursive (slab by slab) fashion     

Modeling and design of arrayed waveguide gratings

The purpose of this paper is twofold. First, a simple but comprehensive and powerful arrayed-waveguide grating (AWG) field model is presented which, based on Fourier optics, borrows some principles of that developed by Takeouchi and coworkers [see, Opt. Express, vol. 6, p. 124, 2000] for the analysis of reflective-type AWGs for optical signal processing, but at the same time adds more features, such as the calculation of device losses and the refinement of the mathematical model to obtain a simple expression for the output field for any input-output waveguide configuration where the meaning of the different high-level parameters of the AWG becomes very clear to the reader. Second, we elaborate on the model developed to present an useful design procedure of the AWG based on two steps illustrated by design flowcharts     

Characterization of charging in semiconductor device materials by electron holography

Quantitative analysis of electrostatic potential in semiconductor device samples using off-axis electron holography in the electron microscope is complicated by the presence of charged insulating layers. Preliminary results indicate that the behavior of p-type material near the Si-insulator interface may differ from that of n-type if the insulator is charging. Coating one side of the sample surface with carbon usually eliminates charging effects. Holographic phase measurements on thin silicon oxide film at liquid nitrogen temperature indicates that the maximum electric field near the edge of an charged region is 18 MV cm(-1), on the order of the breakdown voltage.     

Modulating transistor: a new class of semiconductor device

A new negative resistance transistor n+-p-p?-p structure, consisting of four layers with three electrodes, is reported. The negative resistance effect is due to bulk conductivity modulation. Common emitter, common collector and common base characteristics are described.     

Problems in the analysis of semiconductor device materials exposed to ionizing radiation

Enhanced diffusion of impurities in solids at elevated temperatures under exposure to high-energy particles is well known and is largely attributable to the generation of excess vacancies. This paper deals with the morn subtle effects that can be caused by ionizing radiation (below the threshold for atomic displacements) and can occur even at or below room temperature. In recent years, enhancement of diffusion under the action of ionizing radiation has been observed both in insulators and in semiconductors of the diamond lattice type. It has become evident that analytical results obtained by techniques using strongly ionizing radiation (for instance, electron or ion microprobes), or obtained on samples exposed to ionizing radiaticm beforehand (as in neutron activation work) can be very misleading if the possible alteration of the diffusion profile by the ionizing radiation is not taken into account. Another source of error in neutron activation work is the transfer of impurities from the container material itself to the sample surface, followed by radiation enhanced diffusion into the sample. An attempt is made to give a brief survey of the enhancement effects due to ionizing radiation reported in the literature so far, as well as of the explanations proposed for these effects. Some recent work by the authors is also included.     

Systematic photonic crystal device design: global and local optimization and sensitivity analysis

We present a set of modeling, sensitivity analysis, and design optimization methods for photonic crystal structures based on Wannier basis field expansion and efficient matrix analysis techniques. We develop the sensitivity analysis technique to analyze both refractive index perturbations and dielectric boundary shift perturbations. Our modeling method is /spl sim/1000/spl times/ faster than finite-difference time-domain (FDTD) for searching through a large number of similar device designs. We show that our optimization techniques, relying on the efficiency of the modeling and sensitivity analysis methods, enable systematic global and local optimizations of integrated optical components. We show that our design method can be controlled to favor designs without high-energy build-ups, potentially making them more fabrication-error tolerant. We present design examples and verify our designs with FDTD calculations.     

Microstructured fibre Bragg gratings: analysis and fabrication

A microstructured fibre Bragg grating that relies on a partial and localised etching of the cladding layer along the grating region is proposed. The main effect is the formation of defect states inside the bandgap depending on surrounding refractive index. This leads to the possibility of realising novel optoelectronic devices for sensing and telecommunication applications.