High-efficiency generation of circularly polarized light via symmetry-induced anomalous reflection

Great efforts have been devoted to control the polarization state, the transmission direction, and the phase of light within a very confined space in recent decades. Here, we present a two-dimensional metastructure made of an array of unisized split rings with different opening orientations on the surface of a SiO₂-silver bilayer. This structure possesses an unexpectedly high polarization conversion ratio and generates significantly strong anomalous reflection beams (over 70% of incident light intensity) over a broad frequency range (1100--1750 nm). Functionally, it is able to turn either a linearly polarized incident light or natural light into two perfect circularly polarized beams with the same amplitude yet different handedness to different directions. These features demonstrate a clear example of momentum conservation and can be applied to detect/manipulate the propagation of circularly polarized light.