Inverse-Design and Demonstration of Ultracompact Silicon Meta-Structure Mode Exchange Device

Data exchange among different mode channels is indispensable for optical communication system adopting mode-division multiplexing. Traditional mode exchange device is complex in procedure and large in footprint, which makes it not suitable for dense and large-scale photonic integration. Utilizing the degree of freedom of silicon meta-structure, we design an ultracompact and optically broadband mode exchange device between TE0 and TE1 modes by the step-by-step inverse-design method considering the axisymmetric constraint. Simulation result shows that it is robust to a temperature variation of 100 K and a fabrication error of ±20 nm. The fabricated device is 4 × 1.6 μm2 in footprint. The simulated conversion efficiencies are over 73% and 71% for TE0 to TE1 and TE1 to TE0 within the whole C-band, and the experimental results are about 10% lower than the simulation. 40 Gbps OOK and 25 GBaud PAM-4 data transmission through the device are carried out, which shows good signal quality. We envision that the device...