High-efficiency circularly polarized green light emission from GaN-based laser diodes integrated with GaN metasurface quarterwave plate

We demonstrated high efficient circularly polarized emission from the InGaN/GaN quantum well green laser diode (LD) integrated with GaN metasurface quarterwave plates. Optical properties of the nanoscale thin GaN nanograting metasurface were numerically studied and optimized for a quarter-wave plate. The fabricated nanogratings then were integrated on the emission facet of the LD. Both conversion efficiency and the polarization state of the device were measured, and the conversion efficiency is around 80% while the degree of circular polarization is maintained around 0.99. Our results of achieving a high degree of polarization and a high conversion efficiency at the integrated LD device pay the way for multi-functional applications in bio-imaging, submarine optical communication, quantum communication, and holographic display.