Thermally tunable ultracompact Fano resonator on a silicon photonic chip

A thermally tunable ultracompact Fano resonator on a silicon photonic chip is reported. The Fano resonator is implemented by using an add–drop microdisk resonator (MDR) with the through and drop ports connected by two waveguides and combined via an adiabatic 2 × 2, 3 dB coupler to form a Mach–Zehnder interferometer (MZI). Due to the resonant mode interference between the MDR and the MZI, a Fano resonance with an asymmetric line shape resulted. A p-type-doped microheater is incorporated in the MDR to achieve thermal tunability. By tuning the direct current (DC) voltage applied to the microheater, the Fano resonance is tuned. The proposed Fano resonator is designed, fabricated, and characterized. Measurement results show that a Fano resonance with an extinction ratio of 30.2 dB and a slope rate of 41 dB/nm is achieved. When the microheater is tuned by tuning the DC voltage with a power from 0 to 22.9 mW, the Fano line shape is largely tuned with the Fano parameter q tuned from negative to positive and a maximum wavelength shifting as large as 15.97 nm. Thanks to its ultracompact configuration, and strong and fast tunability with low power consumption, the integrated Fano resonator holds a high potential for applications such as on-chip optical switching and sensing.