电流调制激光自混合光栅干涉位移测量研究

Research on Displacement Measurement of Current Modulated Laser Self-mixing Grating Interference

本文提出了一种激光自混合光栅干涉仪.通过利特罗结构设计,光栅衍射光沿入射方向原路返回激光器,和腔内光混合产生激光自混合干涉效应.由于光栅多普勒效应导致干涉相位随光栅沿光栅矢量方向上的位移而改变.为了提高测量的精度,通过正弦调制半导体激光器的驱动电流,调制激光自混合干涉信号的相位,并引入了傅里叶分析的方法解调相位,最终实现了光栅位移的重构.激光自混合干涉的机制和利特罗结构设计保证了整个光学系统的紧凑性和自准直性.实验结果表明,测量系统的位移噪声水平在50 nm以内.

A self-mixing grating interferometry with current modulation is proposed to measure one-dimensional displacement in this paper.Through the design of the Littrow configuration,the grating diffracted light returns to the laser in the original direction along the incident direction,and laser self-mixing interference effect occurs when the reflected light mixes with the light inside the cavity.The interference phase changes with the grating’s movement in the grating vector direction because of grating Doppler effect.To improve measurement accuracy,through sinusoidally modulating driving current of a semiconductor laser,the output wavelength is also changed sinusoidally.The phase of the interference signal is also modulated,then Fourier analysis method is introduced to demodulate the phase and finally achieve the restoration of diffraction displacement.The mechanism of laser self-mixing interference and the design of Littrow configuration ensure the compactness and autocollimation of the entire optical system.The experimental results show that the displacement noise level of the measurement system is within 50 nm.