Optimal design and experimental demonstration of a silicon-based ultra-compact mode splitter

Abstract

To improve the flexibility of the mode division multiplexing (MDM) system, we propose and experimentally demonstrate a mode splitter by using the inverse design method. The proposed mode splitter has an ultra-compact footprint of 5 × 3 µm2, and the functional region occupies a footprint of only 5 × 1 µm2. The optimized mode splitter can separate the TE0 and TE1 modes without changing the mode order. When transmitting the TE0 mode, the measured insertion loss and crosstalk are 2.14 dB and −13.34 dB, respectively, at the operating wavelength of 1550 nm. The 3-dB bandwidth is >66 nm, and the crosstalk is lower than −12.37 dB over the C + L band. When transmitting the TE1 mode, the insertion loss and crosstalk are 3.04 dB and −16 dB, respectively, at 1550 nm. The 3-dB bandwidth is >57 nm, and the crosstalk is below −12.89 dB over the whole C + L band.