Ultrabroadband Compact Graphene–Silicon TM-Pass Polarizer

Graphene is treated as an anisotropic material because it is one atom thick and its π electrons cause electric conduction in its plane. Based on the polarization-dependent absorption, we design compact broadband transverse-magnetic (TM)-pass polarizer by exploiting a graphene-silicon horizontal slot waveguide structure on silicon-on-insulator (SOI) platforms. The interaction between light and graphene is greatly enhanced by placing the double-layer graphene sheets adjacent to the slot waveguide. The selection of the geometric parameters (e.g., waveguide width, silicon, and Si
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N
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thicknesses) is discussed. We study the mode properties, extinction ratio (ER), bandwidth, and insertion loss. The graphene-silicon slot waveguide based polarizer offers the performance of high extinction ratio, low insertion loss, broad bandwidth, small footprints, and compatibility with an SOI platform. By employing a 150 μm long graphene-silicon horizontal slot waveguide, the ER is higher than 40 dB, and the insertion loss is less than 3 dB over the 1450-1650 nm wavelength range. We also analyze the impacts of practical fabrication imperfections on the operation performance, i.e., fabrication error tolerance, and give the possible fabrication process of graphene-silicon horizontal slot waveguide based polarizer.