An Efficient, Fast-Responding, Low-Loss Thermo-Optic Phase Shifter Based on a Hydrogen-Doped Indium Oxide Microheater

Thermo-optic (TO) phase shifters are very fundamental units in large-scale active silicon photonic integrated circuits (PICs). However, due to the limitation of microheater materials with a trade-off between heating efficiency and absorption loss, designs reported so far typically suffer from slow response time, high power consumption, low yields, and so on. Here, an energy-efficient, fast-responding, low-loss TO phase shifter is demonstrated by introducing hydrogen-doped indium oxide (IHO) films as the microheater, and the optimized electron concentration with enhanced mobility endows the IHO with high conductivity as well as high near-infrared (NIR) transparency, which allow it to directly contact the silicon waveguide without any insulating layer for efficient tuning and fast response. The TO phase shifter achieves a sub-microsecond response time (970 ns/980 ns) with a & pi; phase shift power consumption of 9.6 mW, and the insertion loss introduced by the IHO microheater is & AP;0.5 dB. The proposed IHO-based microheaters with compatible processing technology illustrate the great potential of such material in the application of large-scale silicon PICs.