Polarization-Controlled Surface Grating VCSELs Under Unpolarized and Polarized Optical Feedback

The polarization control of a surface grating vertical-cavity surface-emitting laser (VCSEL) and of a nominally identical standard VCSEL without a surface grating are compared for unpolarized and polarized optical feedback with different feedback levels in the long external cavity regime. While the polarization of the standard VCSEL is strongly influenced by isotropic feedback with a feedback level of just 1% and can even be controlled by polarized feedback, the surface grating VCSEL remains polarization-stable under isotropic feedback. Its polarization can only be disturbed by optical feedback polarized orthogonal to the polarization of the solitary surface grating VCSEL for feedback levels exceeding 18%.