Tunable clockwise–counterclockwise mode degeneracy lifting in optical ring resonators

Microring resonators are fundamental components in modern silicon photonic integrated circuits. Here, we present a reconfigurable silicon microring resonator that leverages a delayed back-coupling mechanism, turning intrinsic backscattering into a versatile design tool. By employing dual injections and tuning the phase between each injection arm, we lift modal degeneracy and achieve independent control of clockwise (CW) and counterclockwise (CCW) modes. This approach enables selective mode suppression, tunable spectral shifts, and bidirectional resonance control. Experimental results closely match simulations, demonstrating robust phase-controlled resonance engineering for advanced spectral signal processing.