Decoupling Beam Pointing Jitter From Intensity Noise in Atomic Comagnetometers Using Flat‐Top Beam Shaping

ABSTRACT

Spin‐exchange‐relaxation‐free (SERF) atomic comagnetometers are essential for ultrahigh‐precision angular‐rate measurements, requiring stable pump‐laser power for long‐term accuracy. Power‐stabilization schemes using a ring‐structured photodetector (Ring PD) avoid temperature‐induced crosstalk, but the steep edge gradient of a Gaussian beam converts minute beam‐pointing jitter into closed‐loop intensity noise. In this work, a nonlinear coupling model between beam‐pointing jitter and intensity noise is developed, revealing the amplification mechanism by which the Gaussian edge gradient transforms beam‐pointing jitter into intensity noise. A laser power‐stabilization architecture combining flat‐top beam shaping with a Ring PD is then proposed. Reshaping the beam into a super‐Gaussian profile minimizes the intensity gradient at the detection boundary, intrinsically suppressing the feedback path that injects beam‐pointing jitter into the control loop. The architecture also improves spatial uniformity of the transmitted pump beam and optimizes atomic polarization distribution in the vapor cell. Compared with the Gaussian‐beam scheme, the flat‐top‐beam architecture reduces the relative standard deviation of transmitted optical power from to , and the Allan deviation at 100 s improves from to . This work provides a robust route for overcoming the long‐term‐stability bottleneck in high‐precision SERF inertial measurement systems.