Phase-controlled on-chip interferometric excitation of an infinity-loop microresonator

We present a fully integrated, phase-stable interferometric excitation scheme for photonic resonators on a silicon-on-insulator platform. Using thermal tuning, the device enables coherent excitation from two input ports, allowing estimation of the complex eigenvalues of any non-Hermitian microresonator. This system is demonstrated on an Infinity-Loop Microresonator–a non-Hermitian infinity-shaped microresonator with both lobes coupled to a bus waveguide. We described its optical behavior by means of an extended Temporal Coupled Mode Theory, capturing phase-controlled interference between the excitation fields. This approach allows precise manipulation of the resonator’s spectral response. Our platform not only provides a tool for characterizing non-Hermitian photonic systems but also opens new opportunities for exploring complex topological and programmable photonic devices.