Splitting Arbitrary Polarized Light with a Flat Dielectric Metagrating

The beam splitter is one of the basic optical components. Traditional beam splitters use bulky cubes or plates to realize beam splitting and thereby can hardly be used in a compact optical system. Recently, the beam splitter based on phase gradient metasurfaces has been proposed to split beam with a compact size. However, it is facing challenges on the efficiency and manufacturability. Herein, a beam splitter based on single‐sized flat dielectric metagrating for arbitrary polarizations is proposed. The diffraction efficiency of the fabricated beam splitter reaches as high as 80% for both TM and TE polarizations at peak wavelength. Moreover, it has a broad working wavelength range (455–550 nm) at visible wavelength where the diffraction efficiency is much higher than 60%. Apart from the broadband and high diffraction efficiency, the steering angle can be simply adjusted by varying the periodicity. Splitting light with a flat metagrating enriches the field of flat photonics, opening up new possibilities in applications such as augment reality displays, imaging systems, compact spectrometers, and lidars.