A wide-angle X-junction polymeric thermooptic digital switch with low crosstalk

We present our recent design of a wide-angle asymmetric X-junction for the implementation of a digital-optical switch. The simulated crosstalk in the OFF and ON states are -28 and -26 dB, respectively, at an X-branching angle of 1/spl deg/. Polymeric material benzocyclobutene was used to fabricate our design and its switching property was demonstrated using the thermooptic effect. The measured crosstalk is approximately -24 dB in both states with rise-time and fall-time 140 and 210 /spl mu/s, respectively.     

热光开关及其几种低串扰集成单元的设计

光开关是光网络中的关键器件 ,也是限制光网络发展的重要障碍。文中在概述光开关现状的基础上 ,研究了 1× 2 Y分支器型和 2× 2 MZI型两种热光开关基本单元的原理和结构 ,提出了几种新型的集成光开关单元的结构 ,这些结构的串扰可以和机械光开关相比拟 ,得到 60 d B左右的水平 ,这些结构在集成光开关中的应用将对集成开关的发展产生建设性的影响 ,并在此基础上分析了 N× N开关矩阵 ,对目前的研究状况进行了分析     

聚合物稳定胆甾相滤色液晶光阀的显示研究

本文研究了在平面态和场致向列相之间快速切换的聚合物稳定胆甾相(PSCT)液晶光阀的彩色显示。采用紫外光诱导相分离法(PIPS)制备具有染料掺杂的聚合物稳定胆甾相液晶光阀,通过3种染料在可见光区的吸收作用,对入射白光进行选择性吸收过滤,得到不同颜色的出射光。结果表明:当PSCT处在平面态下,分子螺旋排列,染料对入射光波的吸收不受光波偏振方向的影响,器件具有很强的吸收作用,呈现有色态;当处于场致向列相,染料的吸收作用微小,器件呈透明态,因此器件具有一定的对比度,且不需要偏振片;器件在平面态和场致向列相之间快速切换的响应时间短于7ms。PSCT光阀可以用作滤色器,在多种染料的共同作用下,快速选择滤色得到多种彩色可见光,组成彩色显示平面。     

An electric field tunable switch with liquid crystal infiltrated photonic crystal fiber grating

The nematic liquid crystal（NLC）infiltrated photonic crystal fiber（PCF）used as a switch modulated by electric field is demonstrated.The switch consists of the infiltrated solid core PCF into which Bragg gratings are written.It is confirmed that the switch can achieve an accurate operation through measuring the reflected light with the change of electric field intensity from 1.4 kVrms/mm to 2.1 kVrms/mm.When the electric field intensity exceeds the threshold,the change of only 0.01 kVrms/mm can cause the wavelength shift of 1 nm.It is approved that the switch with such a structure provides a high sensitivity.The reflection peak is stabilized at about 15 dB which is high enough to separate from the factors such as system noise and error,and it can improve the control precision.     

A 1×8 InP/InGaAsP optical matrix switch with low insertionloss and high crosstalk suppression

We present a current controlled passive 1×8 InP/InGaAsP optical matrix switch for routing applications at wavelength 1.55 μm. It is realized in a tree architecture and has integrated tapers for efficient fiber butt coupling. An AR coated device has average fiber-chip-fiber insertion losses of 6.8 and 6.3 dB for TE and TM polarizations, respectively. The homogeneity of the eight outputs is better than 0.3 dB in each polarization state. The crosstalk suppression is better than 19 dB. The performance of the device indicates that large InP-based switching matrices can be realized     

液晶盒表面取向排列对光敏混合液晶全光开关性能的影响

利用混合液晶,实验研究了间隔厚度为125μm的向列相液晶(NLC)盒的无定向排列、平行排列和扭曲排列3种表面取向 排列方式对全光开关性能影响。全光开关采用光 敏混合液晶(15% BMAB,85% NLCs)注入NLC盒制作而成。实验结果表明,无定向排列NLC盒 和扭曲排列NLC盒都可实现全光开关效应;扭曲排列NLC盒的表面取向作用不仅可以提 高全光开关的稳定性和重复 性,还可以提高全光开关的调制深度和响应速度;相对无定向排列NLC盒,扭曲排列NLC盒 制作的全光开 关的稳定性和上升响应速度分别提高了1倍,调制深度提高了4.8dB 。实验验证了NLC盒的表面取 向作用可提高全光开关性能,对提高结合光敏液晶和光纤制作光控全光纤器件的性能有重要 指导意义。     

Method of measuring optical switch crosstalk attenuationconsidering polarization variation

This paper describes a simple method for measuring the crosstalk attenuation of optical switches that takes into account the polarization variation of incident light. The method involves the use of a laminated film polarizer (LAMIPOL) and a polarization-maintaining fiber (PANDA). Crosstalk attenuation of 2×2 liquid-crystal optical switches for 1.3 μm single-mode fiber is measured using the proposed method and then conventionally with a polarization controller. The similarity of the results confirms the practicality of the proposed method     

2 × 2 optical waveguide matrix switch using nematic liquid crystal

A 2 × 2 nonblocking optical matrix switch, composed of four elemental switches formed in a slab waveguide, is described. Switching action is based on total internal reflection caused by an electrically controlled change in refractive index of the liquid crystal. Propagation loss was remarkably reduced to 2.3 dB/cm, both by using liquid crystal as a cladding layer and by operating at the 1.31 μm wavelength. The experimental matrix switch exhibited 7.3-7.7 dB insertion loss, -17.3 to -18.2 dB crosstalk, and a 14° switching angle.     

非对称马赫-曾德尔干涉型低串扰聚合物光开关

针对对称马赫-曾德尔干涉(MZI)型光开关工艺制备中形成的光栅结构所引起的导模与辐射模耦合是恶化光开关串扰特性的一个重要因素,提出一种采用非对称的MZI结构来抑止光栅导模和辐射模间耦合的新型聚合物电光开关设计方案。研究结果表明,光开关的串扰可以从-20dB改善到-50dB以上;同时,器件的开关电压也从传统MZI型结构开关电压的1.5Vπ减小到了1.0Vπ。     

Optical add-drop multiplexers with low crosstalk

We propose and demonstrate three new optical add-drop multiplexer (OADM) architectures with simple and compact configuration and excellent crosstalk performance. The OADMs use a single multiport optical circulator and either one or two narrow-band fiber Bragg gratings, depending on the crosstalk requirement     

Low-loss polarisation-maintaining optical fibre with low crosstalk

A low-loss polarisation-maintaining optical fibre with low crosstalk is presented. The minimum transmission loss is 0.35 dB/km at 1.54 ?m and crosstalk is ?32 dB at 1.56 ?m in a 1 km length. The relative refractive index difference between core and cladding is 0.3%, and the modal birefringence is 2.8 × 10?4.     

Polarization-independent liquid crystal lens with four liquid crystal layers

A polarization-independent liquid crystal (LC) lens is reported. There are four LC layers in the LC cell. Two LC layers focus one polarization component of an incident light wave, and the other two LC layers focus the other polarization components. The former two layers are placed interlacedly with the later two layers, so that the inherent position difference between the foci of the two polarization components may become very short. The lens properties are shown experimentally.     

A novel low distortion high linearity CMOS bootstrapped switch

This paper proposes a novel low distortion high linearity CMOS bootstrapped switch, and the proposed switch can alleviate the nonlinear distortion of the on-resistance by eliminating first order signal-dependent variation of the overdrive voltage. Based on a 0.18 μm standard CMOS process, the simulation results show that at 100 MHz sampling clock frequency and 49 MHz input signal with 2 Vpp, the proposed switch in differential mode has a Spurious-Free Dynamic Range （SFDR） of 90.1 dB.     

一种新颖的聚合物分散液晶反射光栅

在制备液晶光开关的基础上,采用聚合物分散液晶(PDLC)与金属反射光栅压合的方法研制了一种新型反射式液晶光栅器件,并对其响应时间、调制电压、不同偏振态和不同入射角情况下的衍射效率等光电参数进行了测试.结果表明,该液晶反射光栅具有电场可调性,当驱动电压小于特定值时仅观察到常规反射现象,当驱动电压大于40 V时器件出现明显的光栅衍射效应,且1级衍射效率最大可到6.7%.实验讨论了入射光的偏振态、入射角度等因素对PDLC光栅衍射效率的影响,同时测试了该液晶反射光栅的电场响应时间为10 ms.     

液晶损耗对可调谐液晶光学滤波器性能的影响

F- P型可调谐液晶光学滤波器是一种小体积窄带宽低压调谐滤波器。液晶作为腔内工作物质,其损耗对器件的性能有重要的影响。文章以F- P干涉仪为基础,分析了液晶损耗对这类滤波器的半强度带宽(FWHM) 和峰值透过率的影响,以利于不同要求的滤波器的设计制作。     

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.     

液晶相移剪切电子散斑干涉术的研究

本文研究了向列型液晶的相位调制特性，并采用平行式向列液晶作为相移器，建立了相移剪切电子散斑干涉计量系统。该方法将相移技术引入到剪切电子散斑干涉术中，提高了检测精度，采用相关纹法求解相位，简化了计算，相移方法简单，可靠，用该系统进行应变场的测量实验，取得了满意的效果。     

Optoelectronic switch with low holding power

A double heterostructure NpnP optoelectronic switching device with low holding power has been fabricated. In the static regime a holding power of 20 nW for a device area of 200 mu m*100 mu m was obtained. This value represents a reduction of four orders of magnitude in holding power compared to previous reported PnpN or PnN structures with equivalent device area. A higher optical sensitivity and a lower optical switching intensity is consequently obtained with these devices.<>