Bandwidth-tunable silicon nitride microring resonators

We designed a reconfigurable dual-interferometer coupled silicon nitride microring resonator. By tuning the integrated heater on interferometer's arms, the "critical coupling" bandwidth of resonant mode is continuously adjustable whose quality factor varies from 7.9×10⁴ to 1.9×10⁵ with the extinction ratio keeping higher than 25 dB. Also a variety of coupling spanning from "under-coupling" to "over-coupling" were achieved, showing the ability to tune the quality factor from 6.0×10³ to 2.3×10⁵. Our design can provide an adjustable filtering method on silicon nitride photonic chip and contribute to optimize the nonlinear process for quantum photonics and all-optical signal processing.