Polarization-insensitive ultra-broadband mode filter based on a 3D graphene structure buried in an optical waveguide

We propose a polarization-insensitive ultra-broadband mode filter based on a 3D graphene structure buried in a few-mode optical waveguide. Our experimental device fabricated by burying an L-shaped graphene structure in a three-mode polymer waveguide provides polarization-insensitive filtering of the fundamental mode, while keeping the higher-order modes, with a mode extinction ratio of ∼ 17 d B over the S + C + L band and beyond.