Use of gratings and periodic structures as alignment targets on wafer steppers

The use of moiré fringe techniques in microfabrication equipment is reviewed with special emphasis on mask-to-wafer alignment. The alignment strategies and associated detection methods of a number of commercial wafer steppers are described and their limitations are discussed. Potential improvements to be gained by holographic detection of grating targets are pointed out and future applications in a dynamic exposure system are proposed.     

2-D Binary Conjugation Holographic Grating Multiplexers for Laser Coherent Imaging Systems

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Application of Multimode Laser Diodes in the Interrogation of Fiber Bragg Grating Sensors

The interrogation of fiber Bragg grating sensors with multimode laser diodes is theoretically and experimentally analyzed using two different approaches: serrodyne and dithering techniques. It is also demonstrated that by using several laser modes it is possible to enhance the measurement range without compromising sensitivity.     

Photopolymerizable glass with high refractive index species: Optical performance and emerging implementations

The properties of a photopolymerizable glass modified with high refractive index species incorporated at molecular level, including a wide range of spatial frequencies and the recording kinetics, are analyzed. Implementation of emerging applications is proposed. The article is published in the original.     

高质量莫尔条纹信号的提取

本文分析了影响光栅信号质量的主要因素,指出了获得高质量光栅信号的途径,提出了一般设计方法及各参数的选择。文中给出的实验测试结果成功地用于JC-1型精密测角仪中。     

机载小型化快速反射镜用微位移测量传感器设计

为了实现机载小型化FSM的闭环控制,设计了一款小体积、高精度、高环境适应性的微位移测量传感器。首先根据位移传感器的技术原理和机载FSM的应用需求,提出了微位移测量传感器的主要设计指标。然后,分别对微位移测量传感器的发光元件、密珠滑轨、测量光栅和接收元件等进行了详细设计与选择。其中,高精度密珠滑轨的采用不仅减小了测量过程中的附加阻力,而且使光栅副的运动更加精准;光栅副通光窗口的引入、独特零件编码的设计、裂相法信号提取方式的采用,保证了微位移测量传感器的高低温性能。最后,针对微位移测量传感器在机载小型化FSM上的应用效果进行了理论分析与实验检测。结果显示:机载小型化FSM的方位指向误差不超过3.4″,俯仰指向误差不超过3.8″,证明了专用型微位移测量传感器高精度、高分辨力和高响应速度的技术特点,满足机载小型化FSM的应用需求。     

平面变间距光栅的夫琅禾费衍射场分析

采用对单缝衍射结果进行直接叠加和根据标量衍射理论进行严格积分的两种方法进行推导,分析平面变间距光栅的夫琅禾费衍射场光强分布.在光栅各周期狭缝宽度δ0相差不大时两种方法得到的光强分布差异不大;但当δ0变化较大时,虽然零级衍射中心重合,但是在其他级次,如一级衍射极大的光强在峰值大小和位置上都表现出明显的差异.文中还通过变间距光栅的实例和matlab数值模拟进行分析,根据标量衍射理论通过严格积分将能给出更为普适的结果.在此基础上,联系平面变间距光栅夫琅禾费衍射场的光强分布,对这类光栅的位移传感和自聚焦特性做了介绍.     

Fabrication of highly reflective gratings in 1.5 μm semiconductor lasers using focused ion beam-based etching

This paper reports on fabrication of semiconductor/air gratings in 1.5 μm double-section semiconductor lasers to achieve a high reflectivity in order to compensate low round-trip gain. Fabrication of the gratings with varying thicknesses and with thicknesses down to 160 nm is carried out at the gain section of the double-section diode laser using focused ion beam etching (FIBE) and inductively coupled plasma (ICP) techniques. Theoretical results of reflectivity are given for 1.5 μm AlGaInAs/InP semiconductor lasers by adding wavelength dependence of the refractive index into the calculations. We also compare our reflectivity results with that of a commercial simulation program and show a good agreement between them. Our results demonstrate that the gratings fabricated consist of only six air/semiconductor layer pairs and achieve theoretical reflectivity higher than 99%. Due to a high index contrast of the both layers, n_l = 1, n_h ∼ 3.5, a reflectivity bandwidth of >230 nm is obtained in 1.5 μm semiconductor lasers. Finally, lasing operation from AlGaInAs/InP semiconductor lasers with highly reflective grating section is achieved with a low threshold current of ∼8 mA, which is almost three times lower than devices without semiconductor/air gratings.     

变构型飞行器蒙皮多维大尺度变形重构方法

变构型飞行器在执行不同飞行任务时会大尺度地改变机翼结构和蒙皮形状,蒙皮多维大尺度的变形重构是变形飞行器研究中的难点。本文针对这一问题,提出一种基于多芯光纤传感的变形飞行器蒙皮变形形状重构方法。该方法基于多芯光纤光栅应变传感原理,利用传感器上的多个光栅传感点,建立光栅波长漂移和曲率之间的转换关系,实现三维曲线重构。此外,为了重构变构型飞行器多维大尺度变形下的形状,本文研究了将重构曲线转化为飞行器机翼的展开角和翻转角,并结合两个角度和飞行器机翼的长宽等固有参数,通过拟合插值将两个角度变化引起的变形连续化,实现了柔性蒙皮多维大尺度变形重构。同时,本文为了减小温度造成的误差,利用多芯光纤中间纤芯不受拉伸和压缩、只受温度影响的特点,将中间纤芯与旁轴纤芯的中心波长漂移量做差,实现温度解耦。为了验证本文变形重构方法的有效性,对飞行器蒙皮多种不同情况下的变形进行了实验测试,并将形变重构结果与视觉测量进行了对比。研究结果表明,飞行器蒙皮多维大尺度变形重构的平均误差为7 mm,变形角度重构的平均误差为3.6%,可以实现变构型飞行器蒙皮多维大尺度变形重构,该方法在航空航天器等结构变形监测领域具有良好的应用前...