▎ 摘　　要

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 similar to 17 dB over the S + C + L band and beyond. (C) 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement