Multi-channel high-frequency-offset Pound-Drever-Hall locking using gigabit transceivers

We propose an all-digital multi-channel frequency stabilization architecture tailored for the electronic sideband (ESB) Pound-Drever-Hall locking scheme. Leveraging Gigabit transceivers in a Xilinx 7-series field-programmable gate array, a single-bit high-speed direct digital frequency synthesis (S-DDS-HS) is designed to generate phase-modulated ESB RF signals from 1 MHz to 5 GHz in principle. In the single-channel locking experiment, the linewidth of a 689 nm laser is narrowed to ∼3 kHz (1 s, β-line method), and the frequency noise spectrum is indistinguishable from that obtained with a commercial RF source within the noise floor of the frequency stabilization loop. In the multi-channel locking experiment, we demonstrated that the S-DDS-HS architecture enables simultaneous stabilization of multiple lasers of different wavelengths to a single optical cavity, with the additional capability of compensating cavity noise and drift through frequency transfer among different channels, narrowing the locked linewidth to 1.0 kHz. This work establishes an all-digital, highly scalable approach for multi-wavelength laser frequency stabilization in optical atomic clocks, substantially reducing hardware complexity while preserving performance.