激光自混合干涉位相调制技术的研究

【作者】 沈赟华；

【导师】 王鸣；

【作者基本信息】 南京师范大学 ， 光学工程， 2007， 硕士

【摘要】 激光自混合干涉技术（SMI）是一种新型的计量技术，从80年代开始应用于干涉测量。激光自混合干涉是指激光器的输出光被外部物体反射或散射后，其中一部分光被反馈回激光器的谐振腔，反馈光携带了外部物体的信息，与腔内光混合后，调制输出功率变化。激光的自混合干涉来源于激光器的外部光反馈效应，以前人们总是设法消除光反馈的影响，后来逐渐的由消除光反馈的不利影响到主动利用光反馈效应检测物理量，从而形成了一门新的技术。与传统干涉相比，自混合干涉的光学系统仅有一个干涉通道，结构简单、紧凑，且易准直，因此自混合干涉技术受到越来越多国内外学者的关注，被广泛用于位移、速度、振动测量等领域。为了提高测量精度，一些调制解调的方法被引入自混合干涉信号的分析中，现在主要有注入电流调制法和外腔调制法。但由于这两种调制方法本身的缺点，调相的精度难以保证，制约了其应用的范围。把激光自混合干涉理论和位相调制测量技术结合，将电光晶体（LiNbO₃）引入自混合干涉外腔调制，利用晶体的调制性能，能对自混合干涉信号进行有效的位相调制。因此，基于该机理制成的干涉仪具有结构非常简单、紧凑突出特点，在仪器小型化、集成化方面极具潜力。本文介绍了电光晶体的光学和电光性质，利用软件分别对电光晶体、电极和晶体的电光效应进行了模拟，并从自混合干涉和电光晶体调制位相的基本原理出发，将电光晶体引入自混合干涉外腔调制，研究了自混合干涉测量中电光晶体的位相调制技术。实验证明，利用晶体的调制性能，对自混合干涉信号进行位相调制，在很宽的频率范围（20Hz～100KHz）内都能保证很高的调制精度，测量误差小。在此基础上，本文提出了微型位相调制自混合干涉仪的构想，将光学和微机械加工工艺相结合，对微型干涉仪的光路部分，系统布置和微调器件进行了分析，设计了微型位相调制自混合干涉仪系统，使其微型化、集成化、实用化，以适应纳米测量的新要求。更多还原

【Abstract】 The principle of self-mixing interference (SMI) is a new measuring technique which is applied in interferometry since 1980’s. The light emitted from the laser is reflected or scattered from the external target, a portion of the laser output which contains the information of the target back into the laser cavity and mix with the original light in the laser cavity forming the self-mixing effect, and modulate the change of output power. The self-mixing interference comes from the optical feedback effect. People always tried to eliminate the optical feedback effect previously. Gradually people began to make use of it actively to measure some physical quantities, thus self-mixing interference technology was brought forth. Compared to the traditional interferences, SMI includes a simple, single-axis optical arrangement that requires minimal optical components. So it has received more and more attention, and has been widely used for displacement, velocity and vibrancy measurement and ranging.In order to improve accuracy of the self-mixing interference, some measurement methods are introduced into the SMI system. Two methods have mainly been used now: injection current modulation and external cavity modulation. Because of the disadvantages of the two methods, measurement accuracy can not meet the need of application. Combined the basic theories of self-mixing interferometry with phase modulation, and introduced the electro-optic crystal (EOC) into SMI with external laser cavity modulation, we can realize effective phase modulation for a self-mixing interferomence signal. So the self-mixing interferometer based on these theories is simple, compact and especially potential in instrument miniaturization and integration.In the article, we introduce optical and electro-optical properties of the EOC, and simulate the EOC, electrode and electro-optic effect. From the principles of self-mixing interferometry and phase modulation using electro-optic crystals, the article put an electro-optic modulator in the external cavity and analyzes sinusoidal phase modulation using electro-optic crystal in self-mixing interference. It is proved that implementing phase modulation to laser beams using electro-optic crystals can obtain good measurement accuracy over a wide frequency rage(20Hz～100KHz). Combined optics with micro micro-mechanical processing technic, we analyze the beam path, system arrangement and fine adjustment of the self-mixing interferometer, and form micro-interferometer based on phase modulation in self-mixing interferometry. This model is the micromation, integration and applicability of the phase modulation in self-mixing interferometry, and shows good adaptability in resolution of a few nanometers.更多还原