Controlling Four-Wave Mixing through Full Tunability of MEMS-Based Photonic Molecules

Four-wave mixing, a pivotal nonlinear process in optical signal processing, is significantly enhanced in microring resonators due to their inherent high power enhancement. However, these resonators traditionally face challenges in the precise modulation of coupling strength and phase shift within photonic integrated circuits. In this study, we present fully tunable coupled resonators, termed a photonic molecule device, drawing a parallel between the interactions of its optical cavities and those found within molecules. It incorporates an electrostatic micro-electromechanical system (MEMS), allowing for precise control. Unlike previous photonic molecule devices that could not adjust the coupling strength, this is the first device for four-wave mixing that enables tuning of both the coupling ratio and phase. This enables fine-tuning of the coupling strength and resonant frequencies for each microring, providing the advantage of wavelength controllability in the four-wave mixing process, as well as new parameters for optimizing the conversion efficiency. This innovation in tunability markedly broadens the functionality and application range of the four-wave mixing process.