基于双折射双频激光器中的调频回馈位移测量研究

Experimental and theoretical study of displacement measurement based on frequency modulation optical feedback in a birefringence dual frequency laser

提出了一种基于双折射双频激光器中的调频回馈效应的位移测量系统,并在实验和理论两方面进行了研究.实验中保持回馈外腔长度不变,将一四分之一波片置于激光器内腔中,调制内腔长度,激光器的中心频率发生改变,激光器输出强度将发生周期性的变化.研究发现激光强度曲线的波动频率正比于回馈外腔长度与内腔长度之比.当该位移测量系统的外腔长度是内腔长度的6倍时,被测物体每移动半个光波长,激光强度波动12次,系统分辨率可以达到二十四分之一光波长.理论分析与实验结果相符合.研究表明该位移测量系统具有高分辨率、大测量范围、可工作于任意回馈水平等特点.

A novel displacement measurement system based on frequency modulation optical feedback in a birefringence dual frequency laser has been put forward, which has been studied both theoretically and experimentally. A quarter wave plate is placed in the laser internal cavity. When the internal cavity length is modulated and the external feedback cavity length is kept constant, the center frequency of the laser is changed, and the intensity of the laser fluctuates periodically. The fluctuation frequency of the laser intensity is in direct proportion to the ratio of the lengths of the external and internal cavity. When the displacement of the object is one half wavelength with the ratio being six, the laser intensity will change for twelve periods. Thus, the resolution of the displacement measurement system can reach λ/24. A theoretical analysis is presented, which is in good agreement with the experimental results. The system has the advantages of high resolution, large measurement range, operation at all optical feedback levels, and so on.