Bandwidth-Tunable Ultra-Narrowband Microwave Photonic Filter Based on Silicon High-Q Ring Resonators

We propose and experimentally demonstrate a notch microwave photonic filter (MPF) based on two cascaded silicon Euler-bending racetrack ring resonators, exhibiting optimized performance with MHz-level narrow bandwidth and flexibly tunable bandwidth. Through structural optimization of the ring resonators, a high quality (Q) factor corresponding to a 3dB-bandwidth on the order of tens of megahertz, along with tunable bandwidth, has been achieved. Under intensity modulation, two tuning methods are proposed for variably adjusting the MPF bandwidth: either by manipulating the bandwidths of the two rings or by fine-tuning the resonance spacing between the two rings. Both approaches enable precise and dynamic control of the filter bandwidth. Experimental results demonstrate that the notch MPF achieves an ultra-narrow and flexibly tunable bandwidth. The proposed silicon-on-insulator MPF, with its competitive performance, paves a new way for high-performance on-chip microwave signal processing.