Polarization control of GaN-based micro-caivty lasers with top high-contrast grating reflectors

Abstract

We reported on GaN micro-cavity (MC) lasers combining one rigid TiO2 high-contrast grating (HCG) structure as the output mirror. HCG structure was made directly on the GaN without an airgap, designed to yield high reflectance for transverse magnetic (TM) or transverse electric (TE) polarized light. The laser emission was TM polarized with a degree of polarization of 99.2% and had a small divergence angle of 14 degrees (full width at half maximum), under pulsed optical pumping at room temperature. This demonstration of laser operation for the GaN-based MC with an HCG fully exhibited advantages of HCGs for applications in semiconductor lasers at the wavelength from green to ultraviolet regimes.