Multi-functional high-efficiency light beam splitter based on metagrating.

Inspired by the concept of phase-gradient metasurfaces (PGMs), we present a way to design a multi-functional PGM-based light beam splitter (LBS) operating in the optical regime by engineering the anomalous diffraction properties. As an example of a proof of concept, the designed LBS is a purely metallic slit array with gradient slit width, termed metagrating. It is shown that the designed LBS can simultaneously achieve high-efficiency light beam splitting on both energy and polarization, and it has broadband and wide-angle response. In addition, we also show that the Ohmic loss of metals plays an important role in determining the diffraction efficiency of each diffraction order, which is the physics for designing the LBS that can deliver the incident energy equally into the reflection and refraction sides. Our work enriches the existing methods of designing LBSs and particularly provides a route for the design of multi-functional LBSs with high performance.