Dynamics of a bistable VCSEL subject to optical feedback from a vibrating rough surface

TL;DR

This study demonstrates that a bistable VCSEL with optical feedback from vibrating surfaces can significantly enhance microvibration detection sensitivity, enabling detailed surface vibration analysis with high resolution.

Contribution

The paper introduces the use of polarization switching in bistable VCSELs to improve microvibration detection sensitivity and resolution in optical feedback sensing.

Findings

Responsivity increased up to 45 times for small vibrations.

Bistable VCSEL reproduces fine temporal structure of vibrations.

Effective data processing method for vibration waveform reconstruction.

Abstract

The paper presents an experimental study of the temporal behaviour of a bistable vertical cavity surface emitting laser (VCSEL) under the effect of optical feedback coming from vibrating diffusely-reflecting surface. We demonstrate that a VCSEL operating in the regime of polarization switchings caused by self-mixing effects can greatly enhance a responsivity of the detection of microvibrations. For small amplitudes of microvibrations (less than $\lambda$/2, where $\lambda$ is the operating wavelength of the laser), which cause only harmonic (or close to harmonic) oscillations in the laser output outside of the bistability region, the use of polarization switching can increase the responsivity up to 45 times. For the amplitudes larger then $\lambda$/2 the response of a bistable VCSEL well reproduces a fine temporal structure of the self-mixing signal. A procedure of the data processing in the switching regime for the correct determination of the direction of the displacement and for the reconstruction of the waveform of surface vibrations with a basic resolution of $\lambda$/2 is also shown.