Narrowband and High-Rate Entangled Photon-Pair Generation from a High-Q Silicon Microring Resonator

Entangled photon-pair sources are essential components for emerging quantum information-processing technologies. Among various platforms, on-chip microresonators offer strong potential due to their resonant enhancement and suitability for wafer-scale integration. In this study, we demonstrate ultrabright entangled photon-pair generation from high-Q silicon microring resonators. By optimizing the device geometry and coupling configuration to suppress sidewall scattering and selectively excite the fundamental mode, we achieve single-mode resonance with an intrinsic Q-factor of 1.26 × 106 using only standard fabrication processes available in CMOS foundries. The resulting high-Q resonator yields a record-high brightness coefficient of 3.9 × 109 Hz/GHz/mW2. At an on-chip pump power of 240 μW, we obtain a maximum brightness of 22.0 MHz/GHz and a maximum photon-pair generation rate of 9.19 MHz. At a low-pump power of 10 μW, Franson-type two-photon interference exhibits a visibility of 98.0 ± 0.2%, confirming high-quality time–energy entanglement. These results show that narrow bandwidth and high generation rate can be achieved simultaneously in CMOS-compatible silicon photonic sources, thereby advancing their use in quantum repeaters and scalable quantum networks.