Polarization control of 795  nm vertical-cavity surface-emitting lasers by in-phase surface gratings

795 nm vertical-cavity surface-emitting lasers (VCSELs) with in-phase surface gratings are fabricated and investigated theoretically and experimentally. The polarization characteristics of 795 nm VCSELs with various grating periods and depths are analyzed using the rigorous coupled-wave analysis (RCWA) method; the dependence of polarization stability on the profile of gratings demonstrates that the trapezoid grating ridge slightly enhances the orthogonal polarization suppression ratio (OPSR), but increases the threshold current. The fabricated VCSELs with a sub-wavelength in-phase surface grating of a duty cycle of 0.5 show stabilized output polarization at the cost of increasing the threshold current which is in agreement with the calculations. The grating VCSELs with a period of 200 nm and an oxide aperture of 3.43µm×4.39µm produce a single-mode output with an OPSR of 16.6 dB and a slope efficiency of 0.42 W/A at 85°C.