Field-programmable gate array-based residual amplitude modulation suppression and control for compact atomic clocks.

The article focuses on the development and demonstration of a field-programmable gate array (FPGA) fabric implementing a complex modulation scheme for active residual amplitude modulation (RAM) suppression to improve laser locking to optical frequency references. This FPGA-based system integrates all necessary servos for constructing an optical atomic clock and achieves long-term RAM suppression of up to 60 dB, reducing RAM levels to −100 dBc, which significantly enhances the stability of a two-photon rubidium atomic clock by three orders of magnitude. The approach eliminates the need for temperature stabilization or special electro-optic phase modulator designs and maintains stable RAM suppression over extended periods without drift or flicker noise. This technique, compatible with commercial fiber-based modulators, offers a compact, low-cost solution potentially enabling robust, field-deployable high-performance frequency standards.