AI 中文总结
本研究针对微型光泵浦磁强计，建模其腔增强灵敏度并对比四种读出方式，明确了灵敏度增强标度、临界耦合条件及最大增强极限，为优化微型OPM性能提供了理论依据。
AI 中文摘要
微型光泵浦磁强计（OPMs）的灵敏度受限于原子-光耦合较弱，而光腔可增强该耦合。本工作针对填充缓冲气体的微型气室所特有的强碰撞展宽光学跃迁区域，对腔增强OPM的光子散粒噪声受限灵敏度进行建模。以克拉美罗下界为品质因数，在探针光功率与失谐量联合优化的条件下，将腔增强效果与采用法拉第旋转读出的单次通过自由感应衰减OPM进行基准对比。针对法布里-珀罗腔，对比了边带、零差、Pound-Drever-Hall及法拉第旋转四种读出方式，四种方式均给出最优灵敏度增强标度为α√(2ℱ/π)，其中ℱ为腔精细度，0.5≤α≤1为与读出方式相关的 prefactor。该增强效果在临界耦合时达到最大，本研究量化了偏离临界耦合时的性能下降。进一步表明，尽管存在与系综矢量极化率相关的自旋依赖吸收，只要超过推导得出的探针光功率阈值，并随腔精细度增大提高原子失谐量，即可在任意精细度下，于自旋进动全过程维持近临界耦合。本研究还确定了由矢量光移噪声设定的最大腔增强极限。
英文摘要
The sensitivity of miniaturized optically pumped magnetometers (OPMs) is limited by weak atom-light coupling, which an optical cavity can enhance. In this work, we model the photon-shot-noise-limited sensitivity of cavity-enhanced OPMs in the regime of strongly collisionally broadened optical transitions, characteristic of buffer-gas-filled miniaturized vapor cells. The cavity enhancement is benchmarked against a single-pass free-induction-decay OPM employing Faraday-rotation readout, with the probe power and detuning jointly optimized using the Cramér-Rao lower bound as a figure of merit. For a Fabry-Pérot cavity, we compare side-of-fringe, homodyne, Pound-Drever-Hall, and Faraday-rotation readout. All four yield an optimal sensitivity enhancement scaling as $α\sqrt{2\mathcal{F}/π}$, where $\mathcal{F}$ is the cavity finesse and $0.5\leq α\leq 1$ is a readout-dependent prefactor. The enhancement is maximized at critical coupling, and we quantify its degradation away from this point. We further show that, despite spin-dependent absorption associated with the ensemble's vector polarizability, near-critical coupling can be maintained throughout spin precession at arbitrary finesse by exceeding a derived probe-power threshold and increasing the atomic detuning with finesse. We also establish a limit to the maximum cavity enhancement set by vector light-shift noise.
Comments18 pages, 5 figures
