A high-resolution displacement sensor based on multiple feedback effect of birefringence dual frequency lasers

摘要

A high-resolution displacement sensor based on multiple feedback effect of birefringence dual frequency lasers has been presented and demonstrated. When the system operates in very strong feedback regime with asymmetric feedback induced by incline of an external feedback reflector in an orthogonal polarized dual frequency laser, the modulation frequency of the laser intensity is seven times higher than what the conventional optical feedback system can achieve, due to multiple feedback effect. A fringe shift will correspond to a displacement of a fourteenth wavelength of the external reflector. The intensity transferring periodically between the two frequencies is studied. One period of intensity transfer can be divided into four states: o-light, o-light and e-light, e-light, and no light, and each polarization state corresponds to λ/56 displacement of the external reflector. According to the appearing sequence of the four states, the movement direction of external reflector can be discriminated. Thus, a novel displacement sensor with a resolution of being as high as 11.3 nm, as well as function of direction discrimination, is believed to achieve.