Dual-channel graphene-based optical metasurface switch at telecommunication wavelengths

We theoretically present the concept of a dual-channel optical metasurface switch operating at telecommunication wavelengths. The switching exploits two Fano resonant peaks produced by two pairs of asymmetric silicon nano-bars stacked vertically with each pair acting as optical resonators. We have explored two types of asymmetricity in silicon nano-bars, viz., asymmetry in width and length. The Fano resonances of these silicon nano-bars could be tuned independently between “ON” and “OFF” states by changing the Fermi potential (E f ) of the graphene sheet placed beneath each optical resonator. Transmission greater than 55% refers to the switch in the ON state, and less than 55% refers to the switch in the OFF state. We also demonstrate four possible combinations for both dual-channel switches, viz., ON–ON, ON–OFF, OFF–ON, OFF–OFF, for both types of optical resonators depending on the potential applied to the corresponding graphene sheet. Therefore, we have shown that any type of asymmetricity of nano-bars could be used to produce the dual-channel selective switch without compromising the performance. Further, we have shown the effect of varying parameters—asymmetry, intermediate thickness, graphene thickness, and temperature—on both resonances and the biasing arrangement by introducing another graphene layer in between.