Ultra-compact power splitting higher-order mode pass filter based on inverse design method

Higher-order mode pass filters and power splitters are indispensable components in mode division multiplexing (MDM) systems. In this work, we report a higher-order mode pass filter based on a 1 x 2 multimode interference (MMI), which can simultaneously perform power splitting. Our device is based on a direct-binary-search (DBS) algorithm, and blocked input TE0 mode while splits TE1 mode into two output waveguides with a 50:50 ratio. The final optimized device has an ultra-compact footprint of 2.88 x 2.4 mu m(2), while maintaining insertion loss <3.50 dB for TE1 mode and transmission extinction ratio between TE1 and TE0 mode >18.6 dB are achieved over the bandwidth of 1500 nm-1600 nm. The compact footprint and high performance of our optimized device make it a critical element for integration with other devices in future MDM systems.