Irrotational nanobricks based high-efficiency polarization-independence metasurfaces

The polarization-independence optical metasurface has attracted great interests due to breaking the polarization limitations. In general, polarization-independence characteristics of metasurface almost always originates from the polarization-independence characteristics of the used resonant antenna itself. In this paper, a novel approach is proposed to achieve polarization-independence metasurface based on the irrotational nanobricks. Firstly, the intrinsic characteristics of a half wave plate has been investigated, which can realize co-polarization transmission of X-linear-polarization (XLP) and Y-linear-polarization (YLP) lights, and cross-polarization transmission of circular polarization (CP) light, simultaneously. Eight high-efficiency silicon nanobricks with the phase shifts over 2 π are designed as the basic unit cell, which have the same transmitted amplitude and phase for the CP and XLP light, and the phase difference for XLP and YLP light. We have also designed the beam deflector, metalens and vortex beam generator, which possess identical function for cross-polarized CP and co-polarized XLP and YLP light, respectively. These results can promote the deeper understanding of metasurface, and give a new method to design polarization-independent optical devices.