高能激光对四象限制导器件的影响分析

为了有效地实施激光干扰,需要确定高能激光对四象限制导器件的影响。分析了由高能激光诱导的四象限制导器件的温升分布。理论分析和数值计算表明,在持续的强激光作用下,会造成光电材料的硬损伤。利用典型的比例导引跟踪系统的系统函数,验证了高能激光对四象限制导器件实施激光干扰的有效性。     

基于三组元可调光焦度器件的变焦光学系统设计

采用矩阵光学理论分析三组元可调光焦度器件的变焦系统的一阶属性，得到了基于系统放大率的光焦度控制方程。结合三组元系统初始参数并以系统球差最小为目标，对其进行了初始结构设计，得到了透镜形状参数的控制函数，然后进行光焦度和像质评价验证计算，最后对设计实例进行了归化对比验证。验证结果表明:对球差最小优化值的求解可信，设计方法为采用可调光焦度器件设计变焦系统提供了参考。     

利用小尺寸电荷耦合器件实现数字全息高分辨成像

为了在降低数字全息显微成像系统成本的同时实现高分辨成像,对像面数字全息显微术的记录与再现过程进行了理论分析,结合系统的点扩散函数,对该系统的横向分辨率进行了分析. 得到了如下结论：像面数字全息显微系统的横向分辨率对电荷耦合器件（CCD）光敏面尺寸变化不敏感;对于常见的CCD 器件,其像元尺寸的变化对该系统的横向分辨率影响甚微. 此外,对像面数字全息显微系统的成像特点进行了分析,结果表明：利用像面数字全息系统可以实现物体信息的完整记录与再现,其成像分辨率及像质优于预放大数字全息系统. 利用搭建的数字全息实验记录系统,从强度及位相两方面对理论分析结果进行了验证,实验结果表明了理论分析的正确性. 关键词： 像面数字全息术 横向分辨率 点扩散函数 小尺寸电荷耦合器件     

新型高效热离子功率器件的性能特性研究

应用固体物理和不可逆热力学理论,研究新型高效石墨烯热离子热电功率器件的性能特性.通过数值求解器件高温和低温端的能量平衡方程,确定器件阴极板和阳极板的温度;分析输出电压和阴极板功函数对器件的伏安特性及两个极板温度的影响,确定器件在最大功率密度和最大效率时的参数特性;折衷考虑功率密度和效率,给出参数的优化取值区间;分析了高温热源温度对优化性能的影响.本文所得结果可为热离子能量转换器件的研制提供理论指导.     

阻尼型高温直流超导量子干涉器磁强计的设计

理论分析了超导环路与一个电阻并联结构的直流超导量子干涉器(dc-SQUID)的特性.给出了这种阻尼型dc-SQUID的电压噪声谱密度、传输函数和磁通噪声谱密度随偏置电流变化的曲线.与无阻尼型高温器件比较，调制参量β大于1的阻尼型高温dc-SQUID磁强计具有高稳定性和易调试等优点.当β大于4时，因传输函数的增大，阻尼型dc-SQUID还能降低它的磁通噪声谱密度从而提高磁强计的检测灵敏度.根据现有高温超导薄膜器件的工艺条件，设计了β等于4的阻尼型高温dc-SQUID磁强计的芯片、其磁通噪声和磁场噪声的理论值 关键词：     

C72 富勒烯的电子结构与电子传导研究

本文利用基于密度高泛函理论(DFT)和非平衡格林函数的第一性原理方法对富勒烯C72分子及连接电极构成的C72分子器件进行了电子结构及电子输运性质的研究.计算出了电子透射谱和分子轨道分布,分析了器件的电子结构和输运性质的产生原因. 结果显示C72分子器件的电子传输主要集中在分子壳上. 伏安曲线显示C72分子具有半导体特征.     

无电极电光M-Z型电场传感器LinbO3波导折射率变化研究

利用微扰近似法，导出了折射率的变化公式，通过数值计算，分析并讨论了电场与折射率变化的关系。得出了其函数关系式，通过对实验室制作的器件进行直流测试，进一步验证了函数关系式的正确性和无电极电光M－Z型电场传感器的可行性。     

激光测头用二元准直透镜的研究

通过分析现用激光测头光学系统中所存在的制约测量范围与测量精度的问题，本文提出用二元长焦深、高分辨率器件取代传统准直透镜以提高测头技术性能，并详细推导了此二元器件的设计方法，给出了相位函数表达式。通过对一个设计实例的轴上光斑变化和光能分布情况的模拟计算，并与传统透镜相比较，说明这种二元器件用作准直透镜能够提高激光测头的技术性能。表明二元光学器件用于不接触测量系统具有巨大优势。     

频率对半导体器件热击穿影响的理论模型

针对半导体器件中的热击穿,通过分析已有的理论模型,把频率对器件热区热产生和热传导的影响引入理论模型.利用格林函数求解热传输方程,同时对余误差函数进行近似处理,求解得到热区温度以及器件烧毁功率与频率和脉冲宽度的表达式.通过数值分析,求解得到不同频率下器件烧毁功率随脉冲宽度的变化规律以及不同脉冲宽度下器件烧毁功率随频率的变化规律,同时给出了频率对器件烧毁功率影响的物理解释.     

拓扑石墨烯电极分子器件输运特性

利用密度泛函理论结合非平衡格林函数方法,研究了不同拓扑能带结构的石墨烯电极分子器件输运特性.结果表明器件导通电压与电极禁带宽度正相关,同时器件在输运过程中表现出负微分电阻特性,峰谷电流比可达2697.分析认为器件导通源自于偏压升高过程中两电极能带匹配.器件负微分电阻特性源自于偏压升高过程中两电极能带交错.散射态分析表明,能带匹配后散射态分布较为离域,有利于电子通过器件.能带交错后散射态局域于电极处,表明电子输运受到抑制.     

BILED／BILD组合回路的光学逻辑运算

利用激光二极管或发光二极管混合双稳态回路(BILD/BILED)的组合,得到了光学多稳态,光学异或逻辑门和光学R-S触发器.这种光电子学的逻辑回路与大规模集成技术完全相容,因此有希望应用于光学信息处理,光通信和光计算.     

Nonlinear frequency conversion in coupled ring cavities

The steady-state distribution of circulating power in coupled, unidirectional ring resonators containing a diode-pumped laser crystal and nonlinear optical elements is computed. The full set of transcendental nonlinear equations describing the interactions between the circulating power and the optical elements is solved by a numerical root find function of a commercial mathematics software. The method allows computation of the output of sequential nonlinear processes such as laser gain, second harmonic generation and optical parametric amplification as a function of the input diode pump power. It is also possible to optimize the nonlinear interaction by selecting the optimum interaction cross-section or crystal length. The circulating power may thereby be re-distributed to obtain the lowest possible passive loss.     

小型超导电源系统退磁保护回路建模与仿真

计算了采用二极管等效电压源模型和等效电阻模型的退磁回路电流响应和二极管功耗,分析了两个模型的特点和差异,在此基础上,为了进一步提高精度,充分考虑了二极管的非线性特性,以实际二极管伏安特性进行曲线拟合建立函数关系式得到二极管非线性模型,代入回路方程并求解。综合对比各模型的仿真结果后,得出采用二极管非线性模型和等效电压源模型能更好地模拟退磁保护响应。     

Nonlinear phenomena of left-handed nonlinear split-ring resonators

We theoretically analyze a two-dimensional periodic structure consisting of period nonlinear split-ring resonators (SRRs) with varactor diode. The diode is loaded into the slit of the SRRs. Then, we demonstrate nonlinear phenomena of left-handed nonlinear SRRs. This paper introduces nonlinear SRRs based on left-handed (LH) media and simulates self-tuning mechanisms, bistable effects in the microwave frequency range. In addition, with the increase of input power, the nonlinear response of the SRRs becomes multi-valued, paving a way for creating bistable tunable metamaterials.     

基于六角格子光子晶体波导的高效全光二极管设计

提出了一种基于六角格子光子晶体波导微腔和Fabry-Perot(FP)腔非对称耦合的全光二极管结构, 它由一个包含非线性Kerr介质的高Q值微腔与一个光子晶体波导中的FP腔组成. 通过有限时域差分方法对其传输特性进行了仿真, 发现通过两腔的非对称耦合可以实现在特定光强度下的正向传输、反向截止的功能. 在靠近微腔方向光入射时, 特定强度的光可以激发非线性微腔的Kerr效应, 改变了Fano腔的共振频率, 从而变成透射状态. 而远离微腔方向光入射, 由于这个不对称的结构造成场局域的分布不对称, 激发微腔Kerr效应的光强还不够, 所以光不能透射. 所设计的全光二极管结构具有良好的性能参数: 最大透射率高和高透射比、光强阈值低和易于集成等.     

Tunable unidirectional sound propagation through a sonic-crystal-based acoustic diode

Nonreciprocal wave propagation typically requires strong nonlinear materials to break time reversal symmetry. Here, we utilized a sonic-crystal-based acoustic diode that had broken spatial inversion symmetry and experimentally realized sound unidirectional transmission in this acoustic diode. These novel phenomena are attributed to different mode transitions as well as their associated different energy conversion efficiencies among different diffraction orders at two sides of the diode. This nonreciprocal sound transmission could be systematically controlled by simply mechanically rotating the square rods of the sonic crystal. Different from nonreciprocity due to the nonlinear acoustic effect and broken time reversal symmetry, this new model leads to a one-way effect with higher efficiency, broader bandwidth, and much less power consumption, showing promising applications in various sound devices.     

A monolithic distributed phase shifter based on right-handed nonlinear transmission lines at 30 GHz

The epitaxial material, device structure, and corresponding equivalent large signal circuit model of GaAs planar Schottky varactor diode are successfully developed to design and fabricate a monolithic phase shifter, which is based on right-handed nonlinear transmission lines and consists of a coplanar waveguide transmission line and periodically distributed GaAs planar Schottky varactor diode. The distributed-Schottky transmission-line-type phase shifter at a bias voltage greater than 1.5 V presents a continuous 0°–360° differential phase shift over a frequency range from 0 to 33 GHz. It is demonstrated that the minimum insertion loss is about 0.5 dB and that the return loss is less than-10 dB over the frequency band of 0–33 GHz at a reverse bias voltage less than 4.5 V. These excellent characteristics, such as broad differential phase shift, low insertion loss, and return loss, indicate that the proposed phase shifter can entirely be integrated into a phased array radar circuit.     

Nonlinear theory for a quantum diode in a dense Fermi magnetoplasma

We present a simple analytical nonlinear theory for quantum diodes in a dense Fermi magnetoplasma. By using the steady-state quantum hydrodynamical equations for a dense Fermi magnetoplasma, we derive coupled nonlinear Schr?dinger and Poisson equations. The latter are numerically solved to show the effects of the quantum statistical pressure, the quantum tunneling (or the quantum diffraction), and the external magnetic field strength on the potential and electron density profiles in a quantum diode at nanometer scales. It is found that the quantum statistical pressure introduces a lower bound on the steady electron flow in the quantum diode, while the quantum diffraction effect allows the electron tunneling at low flow speeds. The magnetic field acts as a barrier, and larger potentials are needed to drive currents through the quantum diode.     

Nonlinear effects of electrolyte diodes and transistors in a polymer gel medium

The polarization curve of an acid-base interface in a hydrogel medium has a diode characteristic. Two of each such electrolyte diodes can be combined to give an electrolyte transistor. When a salt is added to the alkaline or to the acidic part of a reverse biased electrolyte diode, the current response is highly nonlinear. If the salt is added to the acidic side, even bistability can be observed. This bistability can generate complex oscillations in a base-acid-base electrolyte transistor. These nonlinear effects are studied experimentally and theoretically. While the nonlinear salt effect can be explained with the Nernst-Planck equations, to understand the bistable behavior further investigations are necessary. (c) 1999 American Institute of Physics.     

Back-to-back Schottky diodes: the generalization of the diode theory in analysis and extraction of electrical parameters of nanodevices

We report on the analysis of nonlinear current-voltage characteristics exhibited by a set of blocking metal/SnO(2)/metal. Schottky barrier heights in both interfaces were independently extracted and their dependence on the metal work function was analyzed. The disorder-induced interface states effectively pinned the Fermi level at the SnO(2) surface, leading to the observed Schottky barriers. The model is useful for any two-terminal device which cannot be described by a conventional diode configuration.