Experimental investigation of RF phase noise transfer in acousto-optic modulators for atom gravimeters

Phase noise remains a critical limitation in enhancing the sensitivity of atom interferometric inertial sensors. While current analyses of phase noise predominantly focus on Raman laser beat frequency locking processes, a significant oversight persists in characterizing radio-frequency (RF) driving-induced phase noise during acousto-optic modulator (AOM) operation - a standard component used for frequency shifting and rapid switching in atomic interference systems. Through systematic experiments, we elucidate the transmission mechanisms of AOM RF phase noise in atomic gravimeters and quantify its impact using phase noise power spectral density analysis. Key findings reveal that in single-pass AOM configurations, suboptimal beam alignment amplifies RF phase noise accumulation within the 30-40 Hz band due to mechanical resonances in the piezoelectric crystal, resulting in a 31% increase in phase fluctuations relative to optimally aligned conditions. Notably, double-pass AOM configurations suppress alignment-induced noise amplification by over 50%, reducing total laser phase noise contributions to 24.4 µGal/Hz in gravity measurements, with 8.9 µGal/Hz directly attributable to AOM RF noise. These results advance the phase noise modeling framework for Raman laser systems and provide actionable strategies for optimizing optical paths, directly addressing robustness and precision challenges in field-deployable quantum inertial sensors.