Free-Space Beam Steering with Twisted Bilayer Photonic Crystal Slabs

We numerically demonstrate the inverse design of a structure for free-space beam steering, based on twisted bilayer photonic crystal slabs. The structure consists of two photonic crystal slabs that can be twisted in plane relative to each other. By rotating the two slabs in plane, one can diffract normally incident light into different outgoing angles, maintaining most of the power in the desired outgoing channel. Our work shows a novel way of achieving free-space beam steering in a compact structure and indicates the important opportunities in inverse design based on bilayer photonic crystal structures.