Four-wave mixing Bragg scattering for small frequency shift from silicon coupled microrings

Frequency conversion is pivotal in nonlinear optics and quantum optics for manipulating and translating light signals across different wavelength regimes. Achieving frequency conversion between two light beams with a small frequency interval is a central challenge. In this work, we design a pair of coupled silicon microrings wherein coupled-induced modesplitting exists to achieve a small frequency shift by the process of four-wave mixing Bragg scattering. As an example, the signal can be up or down converted to the idler which is 15.5 GHz spaced when two pumps align with another pair of split resonances. The results unveil the potential of coupled microring resonators for small interval frequency conversion in a high-fidelity, all-optical, and signal processing quantum frequency interface.