Thermo-Optic Multistability and Relaxation in Silicon Microring Resonators with Lateral Diodes
Dodd Gray, Ryan Hamerly, Meysam Namdari, Mircea Cătuneanu, Kambiz Jamshidi, Nate Bogdanowicz, Hideo Mabuchi
Abstract
We demonstrate voltage-tunable thermo-optic bi- and tristability in silicon photonic microring resonators with lateral $p$-$i$-$n$ junctions and present a technique for characterizing the thermo-optic transient response of integrated optical resonators. Our method for thermo-optic transient response measurement is applicable to any integrated photonics platform and uses standard equipment. Thermo-optic relaxation in encapsulated waveguides is found to be approximately logarithmic in time, consistent with the analytical solution for two-dimensional heat diffusion. We develop a model for thermo-optic microring multistability and dynamics that agrees with experimental data over a wide range of operating conditions. Our work highlights the fundamental connection in semiconductor waveguides between active free-carrier removal and thermo-optic heating, a result of particular relevance to Kerr soliton-state stability and on-chip frequency-comb generation. The devices studied here are fabricated in a CMOS foundry process and as a result our model is useful for the design of silicon photonic waveguide devices.