Aliasing suppression of GaN-based homogeneous circular polarizer monolithically compatible with surface-emitting lasers.

Single layer homogeneous circular polarizer (HCP) metasurface, which is insensitive to the incident linear polarization angle, is designed and fabricated with GaN epitaxy. The right circularly polarized component of the linearly polarized beam is converted to left circularly polarized light and retained on the optical axis. In contrast, the left circularly polarized component is deflected away with a large angle of 75° after passing through the metasurface. The prominent aliasing effect due to the short wavelength and large deflection angle is suppressed by setting the phase gradient along a high-index reciprocal vector. In the simulation, the average degree of circular polarization out of the HCP is 0.95 from all linear polarization, while that from the experiment is 0.88. The average power efficiency is 50% in the simulation and 40% in the experiment. The insensitivity to the incident linear polarization angle makes the metasurface a strong candidate for the monolithically integrated circular polarizer on the backside of surface-emitting lasers.