Nonlinear switching behaviours in a compact all-semiconductoroptical-amplifier Sagnac interferometer device

Nonlinear switching effects in a GaAs-AlGaAs all-semiconductor optical-amplifier loop device with a multimode interference waveguide amplifier (MMIWA) for closing the loop was investigated experimentally and numerically. The miniaturized device, designed to imitate a nonlinear optical loop mirror (NOLM), has a latency more than one hundred times smaller than that of a NOLM. Also, because it used an MMIWA for replacing a coupler in a conventional NOLM, its operation was quite different from that previously reported. In CW signal operation, the nonlinear switching behaviour resulted from the combined effect of nonlinear coupling in the MMIWA and the amplification and lateral field redistribution of the signal through the loop structure. Efficient self-switching and cross-polarized switching were observed. Numerical simulations showed consistent trends in varying device parameters     

激光回馈纳米级宽度干涉条纹

一般的干涉现象为“反射镜每移动半个波长,出现一个干涉条纹”。介绍了利用激光回馈获得纳米级宽度干涉条纹的方法。系统构成:He-Ne激光器,使用近于全反射的球面介质镜作激光器的回馈镜,且该回馈镜法线和激光束夹分量级的小角度。回馈镜沿激光束位移移动时,激光器的功率发生周期类正旋波动,即产生回馈干涉条纹。回馈镜离激光器越近,条纹越窄,以至于半波长位移中出现40个条纹。对波长为632.8 nm的He-Ne激光器而言,每个条纹宽度为7.91 nm。同时,当回馈镜的运动方向发生变化时,激光的偏振态将在两个正交的方向之间发生跳变。利用此效应,可以实现纳米分辨位移测量和回馈镜运动方向的识别。     

基于波分复用的光纤多防区周界传感系统

提出了一种新的光纤多防区周界传感系统,采用波分复用技术实现了监控防区和通道的扩展。该系统对传统采用单根传感光纤和反射镜的结构作了改进,并扩展了传感光纤的数量,将多根传感光纤分别置于监控领域内的不同防区,每个防区分别用不同中心波长的光纤布拉格光栅作为反射装置,使每根传感光纤工作在不同的波长。利用波分复用器件与技术,多根传感光纤共用一套干涉系统,实现了多个干涉子系统同时、独立的监测。实验结果表明,该系统可以实现多个分散防区同时、独立的入侵检测和定位,信号响应时间小于1ms,不同防区间信号的串扰小于-20dB。     

非准直外腔He-Ne激光自混合干涉

从三镜法布里-珀罗(F-P)腔出发,建立了非准直外腔三重回馈白混合干涉的理论模型,并进行了数值模拟和实验验证.分析了3种情况下影响自混合干涉光强调谐特性的因素:1)准直外腔二,三重回馈;2)非准直外腔二,三重回馈;3)外腔加入λ/4波片时的回馈.实验结果与理论分析相吻合.研究表明,该自混合干涉系统的分辨率达到λ/6;自混合干涉输出信号与腔反射镜的反射率、外腔的准直性以及腔内置入镜片有关;外腔中加入λ/4波片时的自混合干涉信号与非准直外腔自混合干涉信号类似;二,三重回馈自混合干涉信号携带了反射体位移方向信息,因而更易实现位移方向判断.     

He-Ne激光管的失效机理研究

从He-Ne激光管组成工艺和内部器件出发,详细分析了影响He-Ne激光管寿命的各种因素,指出对He-Ne激光管寿命影响最为重要的因素,是阴极溅射和反射镜的污染及损伤.并分析了造成反射镜受污染及损伤的主要原因.在只考虑镜膜表面逐渐变粗糙影响的情况下,文中根据基尔霍夫衍射积分公式导出了正入射时粗糙表面的反射率公式.     

直接数字波形合成中的镜频干扰分析

该文针对数字波形合成信号中的镜频干扰问题展开讨论,着重分析了镜频的形成机理及分布特点,说明了采样率对镜频干扰的影响。在此基础上定量分析了产生镜频干扰的采样率条件,并通过实验结果验证。该分析结果为数字波形合成中的采样率选取提供了新的理论依据。     

新型激光驱动可变形反射镜的模型、研制及特性

介绍了一种新型的利用激光驱动的可变形反射镜.它包括三个部分:以聚脂薄膜为主体做成的2μm厚的镜面,支撑镜面的6μm高栅格状的支撑柱,由光敏材料砷化镓(GaAs)构成的感光底层.同时在镜面与感光底层之间施加偏置的高频交流电压.当感光底层背面被激光照亮时,GaAs中载流子的变化导致镜面与感光底层之间电阻的重新分布,从而镜面与感光底层之间电压发生变化,因此在静电力的作用下镜面将会发生相应的形变.文中分析了此反射镜工作的理论模型,介绍了此装置的制作工艺,并通过实验验证了偏置电压幅值、交流电压频率等参数对可变形反射镜性能的影响.     

用于航空遥感的二维像移补偿镜的设计

在航空遥感中,由于振动、飞行器的运动及相机摆动等原因,相机在曝光时,被摄物影像与CCD之间存在着相对运动,带来了成像模糊及拖尾效应,此即像移.其存在对图像质量及精度都有很大影响,因此,怎样减少像移就成为提高遥感设备性能的重要手段。本文介绍了压电式二维像移补偿镜的工作原理,详细描述了其结构的设计以及功能的实现.设计了PZT压电陶瓷驱动补偿镜的柔性铰链平台,实现了补偿镜对CCD成像像移的二维补偿,并对像移补偿镜模型进行了性能分析,通过实验验证了像移补偿镜的性能.     

傅里叶变换光谱仪动镜驱动控制技术

动镜驱动控制技术是傅里叶变换光谱仪的重要组成部分.本文从干涉成像光谱技术原理出发,介绍了迈克尔逊型傅里叶变换光谱仪动镜驱动技术的进展及其应用情况.提出了新型摆扫式干涉机构动镜驱动系统的方案.基于模糊PID控制策略,给出了此驱动系统的闭环控制实现方法.     

Characteristics of a single-frequency Michelson-type He-Ne gas laser

A new mode suppression configuration is described for producing a single-frequency output from gaseous lasers. This configuration has the form of a modified Michelson interferometer where the basic modification is in the introduction of a third feedback mirror for coupling the two branches of the Michelson. Small path length differences between the two branches of the Michelson are responsible for the mode suppression properties of the device which come about through interference phenomena at the beam splitter. This results in a frequency-dependent power loss out of the beam splitter which can provide for large amounts of mode discrimination. The device is made into an oscillator by introducing gain into each of the two branches of the Michelson. A detailed analysis of the device is given based on the scattering matrix formalism. The results of the analysis give the oscillation frequencies, the degree of mode discrimination, the internal laser radiation intensity, and equations for the output power. Experimentally, a 10 mW single-mode 6328 Å He-Ne Michelson-type gas laser is described. Data on the frequency spectrum, output power, and amplitude stability of a free running laser are given and correlated with theory. While it is shown that single-frequency operation is easily obtained, the device in its present form does not include a means for stabilizing the frequency.     

New insert layer structure OLEDs

An insert layer structure organic electroluminescent device（OLED） based on a new luminescent material （Zn（salen）） is fabricated. The configuration of the device is ITO/CuPc/NPD/Zn（salen）/Liq/LiF/A1/CuPc/NPD/Zn（salen）/Liq/LiF/A1. Effective insert electrode layers comprising LiF（1nm）/Al（5 nm） are used as a single semitransparent mirror, and bilayer cathode LiF（1 nm）/A1（100 nm） is used as a reflecting mirror. The two mirrors form a Fabry-Perot microcavity and two emissive units. The maximum brightness and luminous efficiency reach 674 cd/m^2 and 2.652 cd/A, respectively, which are 2.1 and 3.7 times higher than the conventional device, respectively. The superior brightness and luminous efficiency over conventional single-unit devices are attributed to microcavity effect.     

10 Tera Hertz Operation in One-Dimensional Quantum Interference Transistor (1-D QUIT) Devices

A high performance quantum interference transistor (QUIT) realized using high mobility 1-D MODFET channels is presented. The operation of this 1-D QUIT is based on electrostatic Aharonov-Bohm quantum interference effect. The channel length of the device is smaller than the inelastic coherence length of the electrons in the quantum well wire channel, otherwise scattering will randomize electron's phase and destroy the quantum interference effect. Transport characteristics of the 0.2 μm channel 1-D QUIT are calculated at 4.2 °K and compared with a two-dimensional QUIT device reported in literature. Our calculations show a significant improvement of the transconductance in one-dimensional transistors compared with its two-dimensional counterpart. The maximum frequency of operation of the 1-D QUIT is in the Tera Hertz regime, which makes it very attractive device for high frequency applications.     

引入激光回馈的双光束干涉效应的研究

提出了一种引入He-Ne激光回馈的双光束干涉系统,并在理论和实验两方面进行了研究。实验中对系统中的干涉信号及激光器尾光功率变化同时进行探测。发现当干涉仪的主回馈镜移动时,激光器尾光信号是正弦形波形,而干涉仪输出的是以双峰为一个周期的信号,双峰中一峰总是高于另一峰,并且当主回馈镜移动方向改变时,同一周期中两峰出现的顺序也随之改变。对实验现象进行了理论分析,并模拟出干涉信号及激光自身功率的变化曲线。理论分析及模拟结果与实验结果完全吻合。讨论了利用发现的现象进行测量的可行性,所提出的测量方法易于实现。     

4m口径的SiC主镜翻转装置结构设计与分析

根据4 m口径的SiC主镜特殊的使用要求,设计了一种辅助翻转设备实现其180旋转。首先确定了翻转装置的主体构成包括主体框架、轴向支撑组件和径向支撑结构等。理论分析了反射镜在任意天顶角状态下轴向Whiffle-tree支撑结构和径向吊带支撑力的大小,并分析了使用吊带支撑下吊带对反射镜径向压力的大小。接着在设计实际结构的同时,运用有限元建模、重点分析了主体框架的刚度以及光轴竖直和光轴水平状态下镜子的应力情况以及翻转装置的最大刚体位移,根据分析结果设计了整个翻转装置的详细结构。最后根据设计和分析的结果,加工、安装了翻转装置,并采用加速度计测量了翻转过程对反射镜的冲击情况。实际应用和测试结果表明,翻转装置达到了设计要求,可以为类似的结构设计一定的指导。     

不同土壤类型的粗糙地面电磁散射特性及布儒斯特效应研究

土壤表面散射特性对大地遥感等问题有着重要应用,地面对雷达波束的镜面反射是造成镜像干扰的主要原因,利用粗糙地面的布儒斯特效应将有效削弱镜面反射。采用四成分土壤介电模型计算不同类型土壤的介电常数,以二维高斯粗糙面模拟实际地面,引入锥形入射波来克服粗糙面的边缘衍射;应用基于物理意义的双网格法(PBTG)结合稀疏矩阵规范网格法(SMCG)计算分析土壤类型和湿度对地面散射特性的影响,进一步探究了粗糙地面布儒斯特效应随土壤类型、湿度及入射波频率等的变化关系。分析表明:土壤类型和湿度等因素对地面散射特性及布儒斯特效应均会产生不同程度的影响。研究成果对于不同土壤类型的地面环境遥感探测以及削弱镜像干扰提供了理论支撑。     

High-performance two-wavelength asymmetric Fabry-Perot modulatorwith a decoupled cavity design

We have demonstrated a high-performance two-wavelength asymmetric Fabry-Perot modulator (AFPM) by using a novel decoupled cavity design. In this new design, the middle mirror supplies a back-mirror reflectivity for the short-wavelength modulator and, at the same time, a front-mirror reflectivity for the long-wavelength modulator. The front mirror is designed to be transparent at the long wavelength and reflective at the short wavelength to eliminate the interference between the two modulators. With this decoupled cavity design, we greatly simplified the matching requirement for the two cavities and obtain much more flexibility in the device design. Experimentally, we have demonstrated a two-wavelength modulator operated at 860 and 890 nm with operating voltages of 3.4 and 6.2 V and reflectivity changes of 62% and 44%, respectively     

A collimation mirror in polymeric planar waveguide formed by reactive ion etching

We fabricated and characterized an integrated optical mirror in a polymeric waveguide. A parabola-shaped cavity is etched in fluorinated polyimide using oxygen reactive ion etching. The vertically etched sidewall of the planar waveguide works as a highly reflecting total-internal-reflection mirror, which collimates a diverging beam from its focus. The estimated mirror insertion loss of the demonstrated device is 2.4 dB or less.     

A broad-band waveguide grating coupler with a subwavelength grating mirror

A new diffractive device for light coupling between a planar optical waveguide and free space is proposed. The device utilizes a second-order waveguide grating to diffract the fundamental waveguide mode into two free propagating beams and a subwavelength grating (SWG) mirror to combine the two free propagating beams into a single beam. The finite-difference time-domain (FDTD) simulations show that the SWG mirror improves the coupling efficiency of the waveguide fundamental mode into the single out-coupled beam from about 30% to 92%. A high efficiency (>90%) is predicted for a broad wavelength range of 1520-1580nm. The proposed device is compact (/spl sim/80 /spl mu/m in length) and it eliminates the need for blazing the waveguide grating.     

激光镜镜面粗糙度的干涉测量

开发了一种激光镜镜面粗糙度的全场、非接触干涉测量方法。测量了两面不同粗糙度的铜镜,测出的数据和用６ＪＡ型显微干涉轮廓仪测量的结果相吻合。测量的范围为０．０１～０．１２μｍ,理论上测量的精度可达０．００２μｍ。它对镜面抛光过程的控制有实际意义     

Optical frequency conversion device with asymmetric κ-DBRstructure

An optical-frequency conversion device is fabricated, using monolithically integrated distributed Bragg reflector (DBR) mirrors with different coupling coefficients at the outer sides of the active and the saturable absorber regions. The input-end DBR mirror has a higher coupling coefficient than that of the output-end DBR mirror. The converted light is reflected by the input-end DBR mirror and is emitted only from the output end of the device. This device successfully performs optical frequency conversion when the input TM-polarized light has a wavelength within the wavelength range for which the reflection of the input-end DBR mirror is fairly high for TE-polarized light. The ratio of the converted-light output power for TE-polarized light from the input end to that from the output end is less than -30 dB