Micro-optics for liquid crystal displays applications

Micro-optics have become the key technology in liquid crystal display systems due to its capabilities of miniaturization and design flexibility. Design consideration and experimental results of microoptical components for enhancing the image quality, providing better functions, increasing light efficiency, and generating 3D images in liquid crystal display (LCD) applications are presented.     

非线性液晶聚合物电光调制器

文章描述了透明非线性液晶聚合物的合成，准直和非线性光学性质，给出了液晶事物电光调制器的制作和测试方法及应用。     

二维聚合物分散液晶光子晶体的制备与研究

为了改善现有聚合物分散液晶(PDLC)光子晶体(PC)的制备方法和电光特性,利用532nm激光干涉条纹引发聚合物和液晶的混合物相分离,采用全息两次不等时曝光的方法,即第1次曝光完成后,将样品沿基板中心法线旋转60°进行第2次曝光,制备得到电可调谐的二维三角格子的PDLC-PC。实验结果表明,两次曝光的时间对聚合物和液晶的相分离程度影响很大,用偏光显微镜观察优化条件下制备得的二维PDLC-PC发现,聚合物和液晶在二维空间上呈规则的三角格子周期性分布。用波长为633nm的He-Ne激光器探测得到在未施加电压时不同晶格常数的PDLC-PC的衍射图样,并根据一级衍射的电光变化曲线,可以看到,其衍射效率可以利用电场进行有效的调节。     

切变聚合物网络液晶光阀

针对向列型液晶光阀响应速度慢的问题,提出了一种工作在可见光波段的切变聚合物网络液晶光阀(SLCLV).通过测定其电光响应,这种切变聚合物网络液晶(SLC)的响应时间可达几个毫秒,比相同条件下的向列型液晶的响应速度提高了一个数量级,而且对厚度依赖性小.通过理论分析,提出了SLC的工作原理,介绍了工作在可见光波段的反射式电寻址SLCLV的制作过程.器件的制作工艺简单,可靠性高.在可见光-可见光图像转换系统中,测得这种液晶光阀的帧频可达500 Hz,分辨率为81p/mm.如果能进一步提高制作工艺,这种液晶光阀在高速光学信息处理方面有广阔的应用前景.     

电可调谐的聚合物液晶光子晶体

设计了一个无顶的（top-cut）六角棱镜,棱镜高h=3.73cm ,侧面与底面夹角alfa=66 。利用此棱镜和光全息刻蚀的方法,在光抗材料上制作了对称六角结构、蜂窝结构和椭圆柱非对称等结构的光子晶体;并且在聚合物分散液晶材料上制作了大面积电可调谐的光子晶体结构。该光路系统结构简单、稳定、重复性好。光子晶体的理论干涉模式和实验制作结构相比较,结果吻合的非常好。另外还研究了光子晶体的远场衍射模式和电转换特性,对称的六角衍射模式更好的揭示了光子晶体的六角结构。晶体结构中液晶微滴（droplet）的尺寸最小可到10nm,直流转换电压最小达到13.3V/?m。这对研究电调谐的光子晶体激光器和电光转换装置有非常深远的意义。     

A flexible depth probe using liquid crystal polymer

We proposed a method of making a flexible depth-type neural probe using liquid crystal polymer. Conventional depth neural probes made of metal or silicon have the limitations of a single recording site per shank or the brittleness of the silicon substrate. To avoid these drawbacks, polymer-based depth neural probes have been developed with biocompatible polymers such as polyimides or parylenes. However, those have suffered from the difficulty of inserting the probes into brain tissues due to their high flexibility, requiring mechanical reinforcements. Herein, we report the first attempt to use a flexible material, liquid crystal polymer (LCP), as a substrate for a depth-type neural probe. The LCP-based probe offers a controllable stiffness vs. flexibility and compatibility with thin-film processes in addition to its inherent characteristics such as high reliability and biocompatibility. In the present study, an LCP neural probe was fabricated to have enough stiffness to penetrate the dura mater of rodent brains without a guide tool or additional reinforcement structures. A simultaneous multichannel neural recording was successfully achieved from the somatosensory motor cortex of the rodents. Immunohistochemistry showed that the electrodes could be inserted into the desired regions in the brain.     

聚合物分散型液晶结构紫外光稳定性分析

聚合物分散型液晶组件技术是市面上常用的散射式光开关系统,且常常应用于具隐私保护性之电控切换窗户中。然而对于室外的应用,属于有机高分子材料的液晶材料与聚合物结构对于照射紫外光之稳定性与耐受性值得被讨论,尤其是较少被讨论之高分子聚合物结构的影响。本研究主要探讨不同聚合物结构之聚合物分散型液晶组件在紫外光照射下光电特性的变化,期待可以了解聚合物结构特性随曝光时间的变化并提出适当之改善方法。本实验藉由选择具有高紫外光稳定性之主体液晶搭配紫外固化胶调配聚合物分散型液晶预聚物,分别探讨不同固化胶比例与光强度等固化条件下,组件照射紫外光后对于光电特性造成的影响,以此了解各种聚合物形貌照射紫外光后之光电特性变化。实验结果显示,照射紫外光后,各种聚合物分散型液晶组件之临界电压仅仅些微提升,但下降时间剧烈地提高,以聚合物比例35%、固化强度2mW/cm~2为例,临界电压从15.57V些微提升至18.18V,下降时间从195.12ms大幅提升至925.26ms。此外,本研究亦发现相对于照射前,照射紫外光后之组件的下降时间对于电压施加时间长短相当敏感,且此现象可藉由调整固化光强度与固化胶浓度有抑制之趋势。本研究呈现了各种聚合物分散型液晶组件在照射紫外光后光电特性的变化,并了解聚合物结构的特性变化的影响。     

Constant voltage scaling of FETs for high frequency and high power applications

A constant voltage scaling scheme is examined for the enhancement of frequency and power performance of FETs. For low electric fields, this scheme is self-consistent within Shockley's formulation and improves the overall frequency and power performance figure of merit by a factor of κ⁶ with a κ times reduction in the device area. For high electric fields, the improvement is reduced to κ³ times due to the velocity saturation effect. Reduced breakdown voltage further limit the improvement.     

聚合物分散液晶透明投影屏幕成像原理研究

对施加电场时呈透明态(ON态)的聚合物分散液晶(PDLC)膜用作透明投影屏幕的原理给出定性与定量的描述和分析。在PDLC-ON态测试样品的透光率随入射角变化曲线,发现S偏振光透光率不受PDLC膜的影响,P偏振光透光率随入射角变化受PDLC膜的影响衰减严重,发生散射。建立了P偏振光透光率随入射角度变化物理模型,给出了P偏振光的透光率的表达式。模拟计算得出理论曲线,与实验曲线相符合,进而解释了PDLC-ON态作为透明投影屏幕的成像原理。     

A high performances CMOS CCII and high frequency applications

In this paper, we propose an improved translinear based CCII configuration. Heuristic algorithm is used for optimal sizing regarding static and dynamic performances. PSPICE simulations for AMS 0.35 μm CMOS technology show that the current and voltage bandwidths are respectively 2.6 GHz and 3.9 GHz, and the parasitic resistance at port X (R _X ) has a value of 18 Ω for a control current of 100 μA. The improved configuration is used as a building block into high frequency design applications: a current controlled oscillator and a tunable fully integrable band pass filter. The oscillator frequency can be tuned in the range of [290–475 MHz] by a simple variation of a DC current. The central frequency of the band pass filter can be varied in the range of [1.22–1.56 GHz] and the quality factor vary in the range [8–306] with a simple variation of a DC current.     

基于液晶聚合物的双陷波可穿戴天线的设计

基于超薄液晶聚合物柔性材料,设计了一种满足无线体域网(WBAN)需求的双陷波UWB可穿戴天线。该天线由椭圆形贴片、锥形三叉戟共面馈线和梯形地板组成。通过分别在辐射贴片上蚀刻椭圆开口谐振环和在共面馈线上蚀刻n形槽以实现双陷波特性。该天线采用共面波导的馈电方式,具有良好的共面性,易于与载体共形。经网络矢量分析仪测试结果表明,该天线在3. 1~10. 6 GHz的超宽带频段内回波损耗小于-10 d B的同时,在4. 88~6. 15 GHz和7. 55~8. 51 GHz内拥有双陷波特性,可抑制WiMAX和ITU 8 GHz频段对系统产生的干扰。与以往的可穿戴天线相比,该天线厚度仅为0. 1 mm,且柔性可弯曲。此外,对天线在弯曲情况下进行测试,天线特性基本保持不变。     

聚合物分散液晶膜的弯曲散射偏光效应

实验制备了聚合物分散液晶(PDLC)电控调光膜样品 。测试结果表明,样品散射雾度90%以上;施加电场透明透光率接近 80%;施加弯曲应力半透明最大透光率30%以上。分析了样品施加应力 后出现的弯 曲散射偏光现象,弯曲应力导致双极构型的双极连线有沿弯曲方向的大致沿面取向,使 得液晶 微滴中液晶分子有沿面大致取向,导致液晶微滴的折射率沿弯曲方向与聚合物折射率差别大 造成光散射,而沿垂直弯曲方向与聚合物折射率相等造成光透射。     

聚合物分散液晶薄膜中随机激光辐射的实现

设计制作染料掺杂聚合物分散液晶薄膜激光器件,研究随机激光辐射行为。利用微胶囊法将激光染料、向列相液晶、手性剂、聚乙烯醇混合,制备掺杂两种激光染料的聚合物分散液晶薄膜。利用输出激光532 nm的Nd:YAG倍频脉冲激光器进行泵浦,在582～607 nm波段获得尖锐、离散的随机激光输出,阈值能量约为9 mJ,线宽约为0.3～0.4 nm。对于器件产生激光辐射的机制,利用环形腔理论进行了分析。对比掺杂单种激光染料的聚合物分散液晶薄膜激光器件,实验结果显示,同时混合不同类型的激光染料制备的聚合物分散液晶薄膜,能够实现较宽波段的随机激光输出。     

Second-order distributed feedback polymer laser based on holographic polymer dispersed liquid crystal grating

We report on the fabrication and characterization of a second-order distributed feedback (DFB) polymer laser based on a holographic polymer dispersed liquid crystal (HPDLC) transmission grating. The fine organic grating is fabricated on top of the homogeneous conjugated polymer layer in a one-step process. The device shows surface-emitting, single mode laser emission with a threshold of 13.3 μJ/cm², and the working characteristics merely degrade after 10 months of storage in ambient atmosphere. We further explain the dependence of threshold on pumping length, and demonstrate the small refractive index modulation of this all-organic grating is sufficient to maintain efficient DFB laser action. This simple working structure, combined with large processing area provided by the holographic polymerization technique, is extremely promising in realizing ultra-low cost plastic lasers.     

高双折射液晶化合物的研究进展

近年来,液晶器件的响应速度得到了很大的改善,响应时间已经从25ms减少到3ms甚至更短。虽然这种改善与液晶层厚度的变薄有关,但主要原因应该归因于新型液晶材料的发展和使用。色序液晶显示能产生更高质量的图像,但前提是必须有能快速工作的液晶材料。液晶材料的旋转黏度系数、双折射和液晶层的厚度是影响液晶器件响应时间的3个主要因素。本文以液晶双折射这一因素为主线,从液晶化合物结构的角度介绍了影响液晶双折射数值的若干因素,包括中心环结构、中心基团上的桥键、极性基团和侧位-F对液晶双折射的影响等,延长分子的π电子共轭长度能有效提高液晶的双折射。本文列举了国内外已合成的高双折射向列相液晶的分子结构及双折射值,最后对高双折射液晶的研究进行了展望。     

Design of high-Q 3-D integrated inductors for high frequency applications

Design of 3-Dimensional micromachined inductors on high-(10 KΩ·cm) and low-resistivity(10 Ω·cm) Si substrate fabricated using stress metal technology we have developed [1, 2] is presented. Using high frequency electromagnetic simulation of 3-Dimensional inductors performed by Ansoft HFSS®, we have investigated the effects of number of turns, effective radius, metal line width, and different substrates on the quality factor, Q and self-resonant frequency, f _sr of these inductors. We also have compared the simulated results with the measurement results of 3-D inductors fabricated using this technology.     

用偏光显微术研究聚合物分散胆甾相液晶微滴形貌

制备出较大微滴聚合物分散胆甾相液晶样品,用偏光显微镜观察到该微滴具有奇特的"宝石"形貌。提出聚合物分散胆甾相液晶中液晶微滴有垂面和沿面螺旋新构型,与聚合物分散向列相液晶的双极和辐射分布构型相对应,认为"宝石"形貌可能对应着胆甾相液晶在微滴中呈现沿面螺旋与垂面螺旋构型简并共存多畴形貌。本实验研究具有液晶光学基础研究意义和设计新型液晶器件的实用参考价值。     

High temperature dielectric stability of liquid crystal polymer at mm-wave frequencies

The temperature dependent dielectric stability and transmission line losses of liquid crystal polymer (LCP) are determined from 11-105 GHz. Across this frequency range, LCP's temperature coefficient of dielectric constant, /spl tau//sub /spl epsi/r/, has an average value of -42 ppm//spl deg/C. At 11GHz the /spl tau//sub /spl epsi/r/ is the best (-3 ppm//spl deg/C), but this value degrades slightly with increasing frequency. This /spl tau//sub /spl epsi/r/ average value compares well with the better commercially available microwave substrates. In addition, it includes information for mm-wave frequencies whereas standard values for /spl tau//sub /spl epsi/r/ are usually only given at 10 GHz or below. Transmission line losses on 3- and 5-mil LCP substrates increase by approximately 20% at 75/spl deg/C and 50% or more at 125/spl deg/C. These insertion loss increases can be used as a design guide for LCP circuits expected to be exposed to elevated operating temperatures.