Graphene-based spatial light modulator using optical checkerboard AMC metasurface

Spatial light modulators (SLMs) based on graphene have been intensively studied in recent decades. Artificial magnetic conductors (AMCs), which are usually applied to radar cross section (RCS) reduction in microwave regions, can have arbitrary reflected phase while that of perfect electric conductor (PEC) is 180°in general. Herein, we first demonstrate a graphene-based SLM assisted by checkerboard-like AMC metasurface that operates switchable destructive and constructive interferences. Two AMC structures were designed to have the same reflected amplitude but a phase difference of 180°, leading to the cancelation of light at the superposition areas in spatial domain. The main beam of manipulated light was split to several different directions so that the received signal was modulated to minimum value, which could be referred to ‘off’ state. Through gating the Fermi level of monolayer graphene below the AMC metasurface, the phase difference could be adjusted to 0°while the amplitude difference remained nearly unchanged. Therefore, the constructive interference was formed and contributed to the maximum reflection, achieving the ‘on’ state. Numerical simulations indicated that modulation depth higher than 10 dB was achieved when the Fermi level of graphene was gated to 0.1 eV. The depth kept rising with the increase of Fermi level and got a maximum value of 32 dB at 1 eV. The proposed checkerboard design provides a novel method to manipulate spatial light for modulators, imaging and optical clocking.