双频氦氖激光回馈位移测量系统的实验与应用研究

Feedback displacement measurement system using dual-frequency He-Ne laser

研究了一种全新的纳米尺度位移测量系统。将双折射元件插入He-Ne激光器谐振腔内产生频率分裂效应,使原本单模谐振的激光器输出变成了频差可调的2个正交偏振频率(o光和e光),而形成双频激光器。在激光谐振腔外放置沿激光轴线位移的反射表面,将输出的激光束反射回腔内,以便对激光的光强进行调制,可实现高分辨率非接触式可判向位移测量。提出了一种细分方法,该方法突破了传统干涉系统的衍射极限(1/2波长)。对于633 nm波长He-Ne激光,本系统的理想分辨率为1/8波长(约为79 nm)。

A novel nanometer displacement measurement system is investigated. A birefringence element is inserted into the resonance cavity of a He-Ne laser to generate the frequency split effect which changes the original single mode laser into an orthogonally polarized dual-frequency laser whose frequency difference of o-ray and e-ray is variable. The reflective surface placed out of the laser cavity moving along the laser axial can modulate the intensity of the laser by reflecting the output beam back into the cavity. These new phenomena can be used to realize the high resolution and non-contract measurement of displacement. A novel subdivision method which can break through the diffraction limit （half wavelength） is also proposed. The ideal resolution of the system is around 79 nm for He-Ne laser with 633 nm wavelength. The achievements in the research have set the foundation for the laser feedback interferometer development.