Polarization Switching Dependence of VCSEL on Variable Polarization Optical Feedback

In this paper, the influence of variable-angle polarization-rotated optical feedback on the polarization switching properties of vertical-cavity surface-emitting lasers (VCSELs) is investigated theoretically and experimentally. The optical feedback (OF) level and the rotated polarization angle θ
_p
of OF are considered. Two configurations of OF are used to re-injected parallel and orthogonal polarization modes back into the VCSEL. For the parallel OF, it is shown that polarization switching (PS) of VCSELs' modes can occur at a fixed feedback level and bias current with variable θ
_p
. However, in case of orthogonal optical feedback, PS occurs only at certain values of θ
_p
, particularly when the intensities of two polarization modes become comparable with each other. In the theoretical model for both OF conditions, there is good agreement between the experimental measurements and recent theoretical results reported in the literature.