Flexible coupling ratio in single ring resonator through active vertical coupler

A flexibly coupled semiconductor rectangular ring resonator based on a two-section active vertical coupler is demonstrated. The measured and calculated results show consistently varied thresholds and coupling ratio dependent on coupling length and internal loss. For the same configuration devices, the adjustable range of the coupling ratio widens with the reflectivity of the total internal reflection mirrors; for the same reflectivity, such range widens with the coupling length. The widest range of 0.0076-0.4707 is achieved in the device with m. Flexible coupling should increase the tolerance of device design and fabrication and bring a benefit to very large scale integration.