Experimental observation of differential self-mixing interference signals using a randomly polarized laser: a differential self-mixing interferometry.

Differential measurement has strong anti-interference ability. We report the first, to the best of our knowledge, experimental demonstration of differential self-mixing interference signals using a randomly polarized laser for differential self-mixing interferometry (SMI). In the differential SMI system, the detection light can be divided into interference signals of $p$p-polarized and $s$s-polarized light with identical intensity and pi-shift phase difference. By exploiting such a new experimental phenomenon, we propose a noise-robust and low-cost self-mixing interferometer. Experiments show that the proposed approach can effectively suppress both periodic and aperiodic noise. Thus, the reported phenomenon and approach has a good application prospect in self-mixing interferometers.