Dual-band optical filter based on a single microdisk resonator

We propose and experimentally demonstrate a dual-band optical filter based on a single microdisk resonator. An analytical model is built based on the transfer matrix method and is applied to simulate the properties of such a device. Competition and interference of the dual modes in the resonator lead to dual-band filtering with high isolation. As the finite-difference time-domain simulation illustrates, two low-order resonant modes can be effectively triggered by optimizing the waveguide width and spacing gap between the compact resonator and waveguides. In experiment, a double side-coupled microdisk resonator was fabricated on a nanophotonic silicon-on-insulator platform, and dual-band bandpass filtering is realized with an optical isolation higher than 20 dB and an insertion loss lower than 2 dB. The experimental results agree well with our modeling results.