High-brightness photon-pair source based on high-Q multimode waveguide racetrack resonator

Efficient generation of correlated photon pairs through spontaneous four-wave mixing (SFWM) in silicon devices serves as a crucial resource for integrated quantum photonic technologies. Enhancing the intracavity field in high-quality-factor (Q) resonators enables energy-efficient photon-pair generation, with the photon-pair generation rate (PGR) scaling cubically with the Q factor. In this work, we demonstrate a high-brightness on-chip photon-pair source based on a racetrack resonator with a high Q factor of 1.75 × 10⁵, fabricated on a silicon-on-insulator (SOI) platform requiring only a single-etch process. By combining uniform multimode waveguides with optimized Euler bends, we suppress fundamental mode loss and minimize round-trip cavity dispersion, thereby improving both field enhancement and frequency matching for SFWM processes. With a continuous-wave pump of only 44.67 µW, we achieve an on-chip brightness of 1.54 GHz·mW^-2·nm^-1. These results establish a fabrication-friendly and efficient photon-pair source architecture for integrated quantum photonic systems.