Demonstration of an integrated optical switch in a silicon photonic crystal directional coupler

We demonstrate a silicon photonic crystal (PhC) directional coupler optical switch. By engineering the supermodes of the coupled system to provide a slow-light region, the switch has a total length of just 4.9 μm. Thermo-optic switching with a 20 μs response time via an integrated nickel microheater is shown. The proposed switch uses a silica overlayer and infilling of the etched silicon PhC, rather than the more usual membrane slab geometry. The silica infilling and overlayer provides a vertically symmetric structure and is a more robust solution compared to the membrane geometry. We also show that there is no apparent increase in optical loss due to the silica overlayer, despite operating above the lightline; the insertion loss for the air-bridge and silica-embedded structures are comparable (at 1–2 dB).