Efficient mode exchanger-based silicon photonic switch enabled by inverse design

A novel and energy efficient mode insensitive switch building block is proposed and experimentally demonstrated on a silicon-on-insulator platform. Based on a Mach-Zehnder interferometer, the switch uses a relatively compact mode insensitive phase shifter which includes a mode exchanger. The novel structure realizes the exact same phase shift for all modes by exchanging the modes midway within the phase shifter. The design approach leads to reduced power consumption otherwise not possible. Switching the first two quasi transverse electric (TE) modes simultaneously consumes 25.6 mW of power, an approximately 30% reduction from previous reported demonstrations. The measured insertion loss is 3.1 dB on average with a worst-case crosstalk of -14.9 dB over a 40 nm optical bandwidth from 1530 nm to 1570 nm. The design methodology enables scalability up to four optical modes.