铁电液晶光电特性的电路级分析

建立了铁电液晶的Spice等效电路模型,并基于此模型,分析了温度、光波长以及电压频率3个典型参量对铁电液晶光电响应特性的影响.仿真结果表明,以上3个参量的变化对铁电液晶光电响应有明显的控制作用,该结果与Matlab数值分析结果以及实验结果相符.     

铁电液晶器件阈值特性的等效电路模型研究

提出将通用型电路分析软件移植到光电功能器件的研究方案，基于铁电液晶理论和等效电路模型，实施可测性分析和光电混合仿真。应用方波、三角波和正弦波等不同的电压激励源，控制驱动参数(幅值、周期)，模拟了铁电液晶驱动阈值、透射率和驱动响应的变化过程，分析结果较好地拟合了文献报道的实验结果。     

铁电液晶光电响应特性的电路级模拟

针对铁电液晶 (FELC)的简单物理结构模型 ,借助可变电流源来刻画因指向矢的转动而引起的电流变化 ,构造出相应的等效电子电路 (宏模型 ) ,将电路级仿真系统扩展到光电混合集成回路 .提出采用Pspice电路级分析模拟软件 ,通过控制模型参数 ,应用不同的信号 (方波、正弦波、单或双极性脉冲等 )激励源 ,分别就铁电液晶的端口电特性和光电响应特性实施了动态仿真研究 .FELC模型开关特性的分析结果与已报道的理论与实验基本一致 ,并显示出良好的记忆特性     

铁电液晶光电模式及其应用

铁电液晶因具有低电压驱动下的微秒级响应,近年来得到科研工作者的广泛关注,且有望应用于下一代显示及光子学器件领域。本文介绍3种典型铁电液晶光电模式,分别为表面稳定型(surface stabilized ferroelectric liquid crystal,SSFLC)、螺旋形变型(deformed helix ferroelectric,DHF)及电致解旋型(electrically suppressed helix,ESH)。对各光电模式的工作原理及对应的电光效应进行详细阐述,如双稳及多稳态响应、连续灰阶调制、高对比度开关等。同时,光控取向技术在铁电液晶器件中发挥着至关重要的作用。相较于传统摩擦取向层,光控偶氮染料取向层可实现非接触的、锚定能有效控制的铁电液晶取向,这为铁电液晶器件的无缺陷、大面积均匀取向提供前期基础。因此,高对比度、高分辨率、快响应的铁电液晶器件在未来的场序彩色显示、微型显示、2D/3D显示等领域有着广阔应用前景。     

铁电液晶光地性的电路级模拟

针对铁电液晶（FELC）的简单物理结构模型，借助可变电流源来刻画因指向矢的转动而引起的电流变化，构造出相应的等效电子电路（宏模型），将电路级仿真系统扩展到光电混合集成回路，提出采用Pspice电路级分析模拟软件，通过控制模型参数，应用不同信号（方波、正弦波、单或双极性脉冲等）激励源，分别就铁电液晶的端口电特性和光电响应特性实施了动态仿真研究。FELC模型开关特性的分析结果与已报道的理论与实验基本一致，并显示出良好的记忆特性。     

具有点阵金属镜的FLC光阀特性的研究

研究了具有点阵金属镜的铁电液晶光阀的工作特性。给出了详细的实验测试结果。指出了铁电液晶光阀所具有的时钟开关特性及这一特性对光阀的写入和读出的影响，同时讨论了铁电液晶光阀的读出效率、增益、空间均匀度等重要参量。     

铁电液晶型光电混合系统非线性调制效应的理论分析

在以铁电液晶为非线性介质的光电混合系统中 ,选择正弦调制信号和偏压为控制参数 ,通过数值分析得到了系统的一组非线性效应状态图 ,并给出了相应的分叉、混沌等演化模式。模拟结果表明 ,铁电液晶型光电混合系统对入射光的调制可被控制在不同模式上     

晶体与微声材料

会议录报道了1997年3月3日至8日在波兰的Zakopane 召开的液晶物理学、技术及应用会议上发表的99篇文章。内容主要涉及铁电液晶或反铁电液晶及其手性相位,液晶的分子模拟,液晶的介电现象,液晶匹配和缺陷,适用于光学和光电研究及工程的液晶,显示器和应用等方面。     

铁电液晶显示器记忆特性的Pspice可视化分析

从简洁的铁电液晶SmC^*相力学模型出发，开发了铁电液晶显示器（FLCD）的Pspice可视化系统；通过引入多种激励源，控制激励信号的幅值、脉宽、占空比和取样参数，对FLCD的驱动阈值、状态翻转、透射率、响应时间和记忆行为进行了实时仿真。分析结果表明，系统已理想地拟合了相关报道的实验结果，并显示出良好的记忆和存储性能。本方法将有助于光电混合集成系统的计算机辅助设计研究。     

铁电向列相液晶的研究进展

铁电性是电介质具备的一种自发极化状态，普遍发现于对称性较低的晶（固）体材料体系。流体或高流动性软物质材料通常呈现高对称性，因而与铁电性的要求是相违背的。引入强极性或者铁电性是液晶新材料领域备受关注的策略，对开发新型柔性光电器件具有重要意义，在液晶乃至软物质流体材料中一直充满挑战性。相比于传统的液晶和软物质材料，铁电向列相液晶具备多种变革性性质，包括超高介电常数、强非线性光学响应、低电压驱动以及高流动性等，为开发新型先进的柔性光学和电学器件提供了新的可能性。本文介绍了铁电向列相液晶的发展历史，重点阐述了铁电向列相液晶与分子结构之间的关系、物理拓扑结构及特征物性，总结并展望了铁电向列相液晶的未来应用前景，尤其是在新型存储设备、柔性高端光电子器件、非线性光学等领域具有巨大潜力。     

Analogue-driven bistable ferroelectric liquid crystals

This paper presents a new driving method allowing fast analogue light modulation with bistable ferroelectric liquid crystals (FLC). The method is evaluated using a functional virtual prototyping design flow. First, a surface stabilized binary FLC cell is modeled in VHDL-AMS language on the basis of well-known theories of FLC. Some physical and environmental phenomena are added (e.g. electronic behavior of the cell, temperature, etc.) in order to improve its reliability. Once the model is validated, a virtual prototype of a FLC pixel is performed by associating the model of the FLC cell and the model of an appropriate wave generator. Simulations show that our new driving method works, but with certain limitations. The most critical one seems to be the high temperature dependence of the pixel response.     

Optimization of gray-scale performance in pixellated-metal-mirror FLC-OASLM by equivalent circuit model

An equivalent circuit model of a pixellated-metal-mirror ferroelectric liquid crystal (FLC) optically addressed spatial light modulator (OASLM) is proposed. Using both structure and FLC material parameters of a real device and real material as the simulation parameters, the model is firstly confirmed by good agreement of simulation results and the reported experimental ones, and then utilized to optimize gray-scale performance of the OASLM. The model is developed from an improved FLC equivalent circuit, and has the ability to describe the voltage dropped across the modulating layer and to predict how optical outputs vary over time with the input drive voltage and control image. Simulation results indicate that gray-scale performance of the OASLM is highly dependent on write pulse width. More than 10 gray scales are observed when write pulse width is 100 μs and the number reduces to four when it reaches 500 μs. Other parameters of drive voltage can be set to adjust the region of write light intensity over which gray scales are best produced, and write pulses are found to be primary at high write light intensities, whereas erase pulses are dominant at low write light intensities. Furthermore, although gray-scale performance is weakly dependent on erase-light intensity, the erase light is necessary to ensure a proper erasure of the device and at least 1 mW/cm² is required in this study.     

Transient response of a microwave beam amplifier

A model of a beam amplifier consisting of a chain of lightly-coupled cavities has been studied for initial time response with the aid of a computer. The beam flows through the center-holes of 20 cavities stacked together and coupled so the pass band width would be 5 per cent in an infinitely long chain. The intermediate cavities are externally loaded for stability. The electronic transit angle for each cavity is 3π/4,omega_{q}/omega = 0.1, and the beam-circuit coupling coefficient CBis small. Computations have been made of the steady-state input resistance, gain and bandwidth around the 3π/4 "cold" circuit phase shift frequency, as well as of the transient response for t ≥ 0. Results show 1) at the 3π/4 frequency the voltage in the output cavity overshoots the steady-state value, and reaches its first peak at a time almost exactly equal to the amplifier length divided by the group velocity; 2) at a frequency nearer to cutoff, for which the group velocity is smaller, the voltage does not overshoot, but approaches the steady-state value asymptotically, such that at a time equal to the amplifier length divided by the group velocity the voltage has about 80 per cent of its steady-state value.     

Improved model for kink effect in AlGaAs/InGaAs heterojunctionFET's

The kink effect in an AlGaAs/InGaAs HJFET has been investigated with regard to optical wavelength, temperature and gate voltage. The study reveals that the drain current value measured at the drain voltage lower than the kink voltage increases by irradiating white light onto the device, indicating the irradiation-induced kink effect recovery. The degree of the kink disappearance exhibited a significant optical wavelength dependence. We also found that the kink effect is suppressed either by increasing the temperature or by applying a high gate voltage where parallel conduction takes place. Based on these experimental results, we propose an improved model for the kink effect in an AlGaAs/InGaAs HJFET in which the kink effect is closely related to carrier trapping at the hole traps in the AlGaAs donor layer     

A Ti:LiNbO/sub 3/ optical intensity modulator with more than 20 GHz bandwidth and 5.2 V driving voltage

A broadband and low driving-voltage Ti:LiNbO/sub 3/ optical intensity modulator is described. A coplanar waveguide with a shielding plane is used for optical-electrical velocity matching and a confined waveguide is used for lowering the driving voltage. The relationship between the mode size of the guided wave and the driving voltage is shown. This modulator has an electrical 3-dB bandwidth of more than 20 GHz and a driving voltage of 5.2 V at a wavelength of 1.5 mu m.<>     

Automatic frequency control in a semiconductor laser and an optical amplifier

Automatic frequency control (AFC) in an injection locked or resonant type amplifier in an AlGaAs semiconductor laser was achieved through using the terminal voltage change induced by light injection. Signal-to-noise ratio in the control signal of 10 dB was obtained when the input optical power was -47 dBm and the optical gain Was 51 dB. The AFC was maintained for 3 h with an 0.3-percent output power fluctuation for 2°C ambient temperature change and 65-MHz frequency stability. Step response showed that the system response time was 1.5 s. Sensitivity to input optical power deteriorates at -49 dBm, with a 53-dB locking gain, because of frequency deviation caused by temperature modulation. The second derivative of the induced voltage and it's relation to the optical frequency is constant at5 times 10^{-10}[V/(MHz)²] for all input power levels in a buried-heterostructure (BH)-AlGaAs laser. Terminal voltage change induced by light injection is calculated by simple rate equations with a Gaussian-Halperin-Lax (GHL) bandtail model. Good agreement with experimental results was seen.     

-Si∶H摄象管靶的光谱响应和最佳靶厚

用动态系统测量了-Si∶H靶电压对光谱响应的影响,发现对短波响应影响较大。推导了靶光电流is和饱和电压Vs的计算公式,发现Vs[(p,p)-1,2]。从测量的Vs值,计算了pp值。发现它随入照光波长的缩短而减小。估算了对单色光和对白光的最佳靶厚。     

压电式射流激励器工作特性的实验研究

实验设计了压电式合成射流激励器及压电振子振幅测量系统和合成射流速度测量系统.此射流激励器为换能装置,产生的合成射流速度与电参数如驱动频率、信号波形、驱动电压等因素有关.只有驱动频率在一定范围内时才会产生射流速度,且存在着最佳的驱动频率;方波与正弦波、三角波相比可产生更大的射流速度;合适的射流口尺寸也可提高射流速度.     

旋转轮胎中压电悬臂梁离心距优化

针对压电悬臂梁在低频区域内响应较差的问题,该文基于自调节随机共振提出了一种在旋转轮胎中优化悬臂梁末端磁铁离心距的方法。首先分析推导出了末端磁铁的动力学方程,然后以Kramers逃逸速率为基础,建立了自调节随机共振频率与旋转频率的优化函数,得到最优离心距匹配机理,最后运用最优离心距匹配机理得到最优离心距,并比较了不同离心距下压电悬臂梁的位移、速度和电压响应。结果表明,当离心距达到优化值时,在某一频率范围内,随机共振频率随着旋转频率可持续产生共振现象,其有效响应频带扩展至30~50 rad/s,拓宽频带比约40%,有效提升了能量俘获性能。