Experimental demonstration of higher order-mode pass filter based on mode-scattering evolution

A higher-order mode (HOM) pass filter is a key component in on-chip mode-division multiplexing (MDM) systems, enabling mode-selective transmission. In this study, a highly integrated silicon-based HOM pass filter is proposed based on "mode-scattering evolution." The proposed filter consists of a functional region and input/output waveguides, with a compact footprint of only 2 µm × 9 µm achieved through an inverse design. Experimental results demonstrate that the fabricated silicon-based HOM pass filter exhibits an insertion loss of 2.11 dB and a crosstalk of -10.63 dB at 1550 nm. The bandwidth with a loss <5 dB is measured to be 90 nm. The proposed device offers an efficient solution for on-chip mode-selective filtering, which can provide a promising technology for building integrated MDM systems.