Electrical polarization control of VCSELs based on an orthogonal switching liquid crystal layer

Abstract

Stable polarization has been regarded as a key element for improving the beam quality of vertical cavity surface emitting lasers (VCSELs). However, gain isotropy in the active layer of VCSELs ineluctably leads to the uncertainty of the polarization direction. In this paper, a liquid crystal (LC)-VCSEL laser with polarization control characteristics is designed and fabricated based on the optical rotation effect and electrically controlled birefringence characteristics of orthogonal LC. The experimental results show that, electrically controlled LC could flexibly realize the scheme of polarization stable output and the switching ratio of polarization output could reach 164:1. Based on the electrically controlled birefringence characteristics of LC, the linear polarization angle of VCSEL is further regulated by applying a deflection voltage, and the polarization angle tuning range is between 0° and 90°.