Optical-comb-based frequency stability transfer across the spectrum with a multi-channel FPGA.

Using the optical comb as a transfer oscillator is an effective approach to convert the spectral properties of ultrastable lasers to other wavelength domains. We describe a digital locking system that enables this process to be replicated for several lasers at a time, supporting the simultaneous and independent lock of up to 6 lasers to a single, high performance reference oscillator. The locks are robust, easily reconfigured and contribute a short-term instability lower than 3 × 10 at 1 s, even when the comb is operated in the broad-linewidth regime and with no need for pre-stabilization of slave lasers. With this system we transfer the coherence of the ultrastable clock laser of a Yb optical lattice clock at 1156nm to various slave lasers in the 1550nm region, including the one used for frequency dissemination with long-distance fibers, with less than 1 × 10 instability at 1 s. The digital implementation enables a modular approach with enhanced control over operational parameters, minimizing setup complexity and hardware-related undesired effects. It also allows for immediate reconfiguration and seamless upgrades, being suitable for applications requiring multiple ultrastable lasers at different wavelengths, such as local or distributed optical clock ensembles, coherent spectroscopy, and quantum simulation.