Dense dissimilar waveguide routing for highly efficient thermo-optic switches on silicon

We analyze and demonstrate a method for increasing the efficiency of thermo-optic phase shifters on a silicon-on-insulator platform. The lack of cross-coupling between dissimilar waveguides allows highly dense waveguide routing under heating elements and a corresponding increase in efficiency. We demonstrate a device with highly dense routing of 9 waveguides under a 10 µm wide heater and achieve a low switching power of 95 µW, extinction ratio greater than 20 dB, and less than 0.1 dB ripple in the through spectrum with a footprint of less than 800 µm × 180 µm. The increase in waveguide density is found not to negatively impact the switch response time.