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Abstract

We analyze and demonstrate the performance of dense dissimilar waveguide routing as a method for increasing the efficiency of thermo-optic phase shifters on a silicon-on-insulator platform. Optical, mechanical, and thermal models of the phase shifters are developed and used to propose metrics for evaluating device performance. 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, by thermally isolating the phase shifter by removal of the silicon substrate, 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. The device has a footprint of less than 800 μm x 180 μm. The increase in waveguide density achieved by using dissimilar waveguide routing is found not to negatively impact the switch response time.