2026/06/26 by Mohamad Reza Nurrahman, Hyeon Hwang, Nuri Han +6
#physics.optics
Integrated quantum photonics requires bright, high-fidelity photon-pair sources capable of spectral multiplexing, correlation control, and circuit-compatible extraction. Cavity-enhanced spontaneous parametric down-conversion (SPDC) increases pair generation, but triply resonant operation imposes stringent pump-signal-idler spectral-alignment constraints. Moreover, the trade-off between intrinsic generation and coincidence-to-accidental ratio (CAR) does not capture the usable output flux, which depends on photon extraction. Here, we demonstrate a single-pass-pumped, resonator-enhanced quantum frequency comb (QFC) source based on a periodically poled lithium niobate photonic-crystal Fabry-Pérot microresonator. The device yields intrinsic and loaded brightnesses of 69.9 and 1.88 MHz/μW, respectively, and a maximum CAR of 16,000. Frequency-resolved measurements reveal 461 cavity-defined bins spanning 1495-1570 nm, and loaded spectral brightness approaching 4.29×109 pairs/(s⋅mW⋅nm). Heralded autocorrelation measurements yield a second-order autocorrelation gH(2)(0) as low as 4.0×10-4 for a selected high-CAR cavity-defined bin pair. In particular, tuning the single-pass pump deterministically selects correlated frequency-bin pairings within the fixed QFC grid while preserving brightness and pairwise coincidence rates. We further separate intrinsic generation from output photon-pair flux, revealing the loaded-brightness-CAR relation. Together, pump-selectable bin pairing and extraction-aware loading point to tailored SPDC QFCs as chip-integrated nonclassical light resources for multichannel quantum-state transport and information processing.