Study of nonlinear effects and self-heating in silicon microring resonator including SRH model for carrier recombination

The comprehension of non-linear effects in silicon is fundamental when designing ring resonator in the Silicon- On-Insulator (SOI) platform. The optical field propagating in the ring waveguide suffers strong absorption due to Two-Photon-Absorption (TPA) and Free-Carrier-Absorption (FCA) whose strength is proportional to the input power in the ring. The free carriers generated via TPA can then heat the device through self-heating. In this scenario, we present a new method for the modelling of non-linear effects in silicon based ring resonators. Our numerical approach aims to solve the non-linear problem, which couple the variation of refractive index and losses due to TPA, FCA and self-heating, with trap-assisted rate equations based on the Shockley-Read-Hall (SRH) theory. We show for the first time, that the SRH formulation is capable of predicting the dependence of free carrier lifetime on the power circulating in the ring. The new model is validated by comparing simulation results with experimental measurements on a racetrack microring resonator at steady state and in time domain. By the fitting of the experimental results, we determine the surface trap density to be 3 · 10^{12c}m{−2} assuming donor like trap energy level around 0.9 eV . Through time domain simulation we are able to reproduce oscillations in the output power at the through port caused by the interplay of non-linear effects with self-heating.