Electrically tunable absorber based on a graphene integrated lithium niobate resonant metasurface.

Perfect absorbers are of great importance in various applications such as photodetectors, optical sensors and optical modulators. Recently, perfect absorption metasurface based on monolayer graphene has attracted lots of research interest. In this paper, a graphene-lithium niobate (LN) perfect absorption metasurface is constructed, where graphene works as a thin absorptive layer as well as a conductive electrode. The proposed device achieves 99.99% absorption at 798.42 nm and 1.14 nm redshift of the absorption peak is realized at 300 V(from -150 V to 150 V) external bias voltage through the electro-optical effect of LN, which enables the proposed device work as a electrically tunable absorber in the visible and near infrared range. The switching ratio of reflected light R/R could reach -44.08 dB with an applied voltage tuning from -150 V to 0 V at 798.42 nm. Our work demonstrates the potential of LN integrated high-Q resonant metasurface in realizing electro-optic tunable nanophotonic devices in the visible and near infrared band. It will promote the research of graphene integrated optoelectronic devices as well as LN based tunable nanophotonic devices which have widespread applications such as modulators and optical phase arrays.