A NEW SELF-MIXING MICRO-INTERFEROMETER BASED ON EXTERNAL PHASE MODULATION

摘要

A new self-mixing micro-interferometer based on external phase modulation is presented. Self-mixing interference occurs in a laser diode (LD) by reflecting the light from a mirror-like target in front of the laser. Sinusoidal phase modulation of the beam is obtained by an electro-optic crystal (EOC) in the external cavity. The phase of the interference signal is demodulated by Fourier analysis method. The combination of the modulation and demodulation decreases the sensitivity of the instrument to fluctuations of the laser power and the noise induced by environment. Experimentally, the new micro-interferometer is applied to measure the micro-displacement of a high precision commercial PZT with an accuracy of < 10nm.