Silicon microdisc resonator for thermo-optically efficient widely tunable microwave photonic filters

A compact and energy-efficient silicon photonic microdisc resonator (MDR) has been designed and demonstrated for widely tunable microwave photonic filters. The MDR was integrated with a meander-type microheater for efficient thermo-optic tuning. The experimentally observed loaded Q value of the MDR (radius 5 μm) in all-pass configuration is ~10⁵, and its resonance wavelength (λ_r∼1550 nm) could be thermo-optically tuned with a slope of 351 pm/mW (∼44 GHz/mW). In our experiment, we have demonstrated a microwave bandpass filter of 3-dB bandwidth ∼1 GHz and tunable up to 50 GHz, which is limited mainly due to the bandwidth of the modulator and photodetector. However, the theoretical tuning range of the device is as high as 780 GHz, which is again limited by the higher-order resonance mode coupling to the MDR in all-pass configuration. The device design parameters were optimized such that it could be fabricated in a conventional CMOS fabrication process-compatible silicon photonics technology platform.