Quasicontinuous sub- μ K strontium source without a high-finesse cavity-stabilized laser

We demonstrate a quasicontinuous sub- μ K strontium source achieved without the use of a high-finesse cavity-locked laser. Our frequency reference is based on a dispersion-optimized, fiber-based frequency comb that enables sub-kHz linewidths. The long-term stability of the comb is defined by an external rf reference: either a 10 MHz rf signal from the Dutch Metrology Institute (VSL) or a tunable rf source whose long-term stability is maintained by monitoring and stabilizing the position of a narrow-line magneto-optical trap (MOT) [Sillus , Rev. Sci. Instrum., 92, 033204 (2021); Heizenreder , Continuous cloud position spectroscopy using a magneto-optical trap, Phys. Rev. Appl. (2026)]. The comb-stabilized system is benchmarked against a conventional cavity-locked laser and achieves comparable performance in broadband and single-frequency MOTs using the narrow 1 S 0 → 3 P 1 laser-cooling transition. We generate high-flux, sub- μ K samples of all three bosonic strontium isotopes and demonstrate quasicontinuous outcoupling from the MOT. These results highlight the system’s suitability for compact, robust, and field-deployable continuous cold-atom devices.