Angular interferometer using calcite prism and rotating analyzer

An interferometer using a calcite prism and rotating analyzer is proposed for angular displacement determinations. The calcite prism senses the angular displacements and the rotating analyzer transfers the interference signals from dc-type into ac-type. Compact optical setup and using low-cost devices are thus the advantages of the interferometer. The theory of the interferometer is first demonstrated. A setup constructed to realize the interferometer and the results of using this setup are then presented.     

An enhanced common path interference optic measurement system for refractive indices and thickness

This study proposes a common path interference optical system for the measurement of refractive indices and thickness of uniaxial crystal material. The measurement system comprises an accurate Mach–Zehnder laser interferometer, a single-axis rotary stepping motor, and a computer. The laser interferometer is composed of a single-frequency He–Ne laser, two-beam splitters and two reflectors. The Mach–Zehnder laser interferometer measures the optical length difference by using its linear measurement accuracy. The proposed solution procedure enables both the refractive indices and the thickness of the optical waveplate to be obtained. The proposed design differs from conventional designs in that it does not use a heterodyne modulator with a lock-in technique. It is shown that the refractive indices and thickness of the tested optical elements can be measured rapidly and accurately.     

Study of thermal lensing effects in a copper vapor laser

The thermal lensing effect of the Copper Vapor Laser (CVL) was studied by considering both its windows and the active medium. The equivalent combined focal length of the active medium and windows was measured to be 52 mts under operating conditions for a 35W CVL. The variation of focal length with the operating parameters was studied.     

Holographic visualization of laser-induced plume in pulsed laser welding

High-speed holographic interferometry was applied to the experimental study of a laser-induced plasma plume in pulsed laser welding. We adopted two kinds of holographic interferometers for visualizing and imaging the refractive index distribution of the plume and vaporized metal; a real-time holographic interferometer with a high-speed camera and a double-pulsed holographic interferometer with a dual-reference-beam module. The high-speed photographs of the weld plume were compared with the visualized images by holographic interferometer. The experimental results show the process of generation and propagation of the laser-induced plume and give the feasibility of quantitative measurement of the density distribution of the laser-induced plume and vaporized metal in laser welding.     

Performance evaluation of a wave-front displacement system for vectorial shearing interferometer

We describe a wave-front displacement system using a novel configuration of a pair of wedge prisms. The wave-front propagation, through the displacement system, is analyzed using the exact ray trace. The main advantage, of this configuration, is that the shearing (direction and magnitude) is constant from the displacement system to the image plane. The direction of the shearing depends on the relative orientation of the prisms. The magnitude of the shearing is proportional to the distance between prisms. The proportionality constant depends on the wedge angle and the material of fabrication of the prisms, and it gives the sensitivity to the displacement of the system. The deviation of the shearing due to the difference between the wedge angles is larger than that the produced by the oblique incidence of the wave-front. The experimental results confirm the theoretical data.     

对迈克尔逊干涉仪测量波长实验中几个常见问题的分析

本文分析了迈克尔逊干涉仪测量波长实验中经常遇到的几个问题，并对其产生的原因进行了探讨。     

面向天基引力波探测的时间延迟干涉技术

时间延迟干涉技术(Time-delay Interferometry,TDI)对中国引力波探测项目及其它天基激光精密测量任务具有重要的参考价值。在天基引力波探测任务中,需利用激光干涉仪对无拖曳检验质量块间实现十皮米量级的位移测量精度。其中,激光源频率噪声和时钟频率噪声是两项主要噪声。在欧洲主导的LISA(Laser Interferometer Space Antenna)引力波探测项目中,利用TDI对三星上的十二组相位测量值进行延迟和线性组合,构造出臂长相等的干涉仪,从而消除了激光源噪声以及光学平台位移噪声。为了消除时钟噪声,将时钟信号倍频到GHz,再通过相位调制的方式加载到星间激光链路上,最终从时钟边带拍频信号中提取出时钟噪声,并在TDI的数据组合中将时钟噪声项消除。为了实现TDI的时间延迟处理,要求对星间绝对距离进行精确测量。因此,在TDI机制中,星间激光链路需要同时实现位移测量、时钟边带调制和绝对距离测量3个功能。其中,后两个功能分别大约消耗10%和1%的载波激光功率。LISA项目针对TDI技术的地面论证结果表明,TDI技术对激光源和时钟的噪声抑制分别达到了109和5.8×104倍。     

HL-2M 装置固态亚毫米波干涉系统研制

发展了一套固态亚毫米波外差干涉系统和一种基于全相位快速傅里叶变换(apFFT)的相位处理方法用 于测量 HL-2M 初始等离子体电子密度。该系统采用平面型二极管倍频技术对低频的锁相微波源进行高次倍频以 产生功率大于 0.1MW、频率 306.9GHz 的探测波。基于 apFFT 的相位处理数值算法可以从原始信号中提取相位信 息,缓解由可能的高水平密度扰动导致的相位跳变。系统的固有时间分辨率为 5μs,电子密度测量范围在 10¹⁶~10²⁰m⁻³。在 HL-2M 装置首次实验期间,该系统被安装在中平面上,利用装置内壁反射实现干涉测量,成功 测量了线平均电子密度。      

基于低双折射光子晶体光纤Sagnac干涉仪的超低温度系数扭曲传感器

研究了低双折射光子晶体光纤中由光纤扭曲造成的圆双折射效应,并应用Sagnac干涉仪结构设计了扭曲传感器.在Sagnac环中的光子晶体光纤上施加机械压力引入初始线双折射并产生正弦干涉光谱,再扭曲光纤产生圆双折射使干涉光谱随扭曲角度移动.光谱峰值波长随扭曲角度变化符合Sinc函数关系,理论分析与实验相符.传感器灵敏度为1....     

非接触法自动测量薄膜厚度

根据白光等厚干涉原理,基于单片机改造的迈氏干涉仪用于自动测量透明薄膜厚度,采用非接触性测量法。当迈克尔逊干涉仪静镜形成的虚像与动镜相交所成的夹角很小时,在光屏上看到彩色干涉条纹,插入薄膜后,光程差改变,彩纹消失。步进电机带动微调手轮转动,当彩纹再次出现,即可得出透明薄膜厚度。