Integrated optical filter consisting of micro-ring resonator embedded in Fabry-Perot cavity

An optical filter is proposed and demonstrated based on a micro-ring resonator (MRR) embedded in a Fabry-Perot (FP) cavity. By exploiting coherent interference within the FP cavity to reconstruct the transmission spectrum of the MRR, high extinction ratio (ER) and narrow bandwidth for periodic notch filtering is obtained. The FP cavity is composed by two circular Bragg grating (CBG) mirrors, and the two mirrors are well placed so that the light wave can be constantly reflected between the two mirrors to generate resonance. The device is simulated theoretically and fabricated on a silicon-on-insulator (SOT) platform. The proposed optical filter has an ER up to 31dB and a minimum 3dB bandwidth of 10pm according to the simulation result.