Compact multi-million Q resonators and 100  MHz passband filter bank in a thick-SOI photonics platform

We demonstrate ring and racetrack resonators with Qs of 3.8 to 7.5 million and 100 MHz bandwidth racetrack resonator filters, implemented in a thick silicon-on-insulator foundry platform that features a 3 µm thick device layer. We show that special racetrack resonators (with weakly guiding straight sections that transition to strongly confining bends) implemented in this platform can be preferable to rings for applications such as integrated microwave-photonic signal processing that require filters with sub-GHz bandwidth, tens of GHz of free spectral range (FSR), and a compact footprint for dense system-on-chip integration. We demonstrate ring resonators with 7.5×10⁶ intrinsic Q, but limited FSR of 5.1 GHz and a taxing footprint of 21mm² due to a large 2.6 mm bend-loss-limited radius. In comparison, we demonstrate two racetrack resonator designs with intrinsic Qs of 3.8×10⁶ and 4.3×10⁶, larger respective FSRs of 11.6 GHz and 7.9 GHz, and less than 1/20 the area of the ring resonator. Using racetrack resonators, we implemented a four-channel, 100 MHz wide passband filter bank with 4.2 to 5.4 dB insertion loss to drop ports.