Opt Express. 2021 May 10;29(10):14467-14475. doi: 10.1364/OE.420031.
Optically-pumped magnetometers constitute a valuable tool for imaging biological magnetic signals without cryogenic cooling. Nowadays, numerous developments are being pursued using alkali-based magnetometers, which have demonstrated excellent sensitivities in the spin-exchange relaxation free (SERF) regime that requires heating to >100 °C. In contrast, metastable helium-4 based magnetometers work at any temperature, which allows a direct contact with the scalp, yielding larger signals and a better patient comfort. However former He magnetometers displayed large noises of >200 fT/Hz with 300-Hz bandwidth. We describe here an improved magnetometer reaching a sensitivity better than 50 fT/Hz, nearly the photon shot noise limit, with a bandwidth of 2 kHz. Like other zero-field atomic magnetometers, these magnetometers can be operated in closed-loop architecture reaching several hundredths nT of dynamic range. A small array of 4 magnetometers operating in a closed loop has been tested with a successful correction of the cross-talks.
光泵磁强计是一种无需低温冷却即可对生物磁信号进行成像的有用工具。如今，人们正在使用基于碱金属的磁强计进行大量开发，该磁强计在需要加热到 >100°C 的自旋交换弛豫自由（SERF）模式下表现出了优异的灵敏度。相比之下，基于亚稳态氦-4 的磁强计可在任何温度下工作，这允许与头皮直接接触，从而产生更大的信号和更好的患者舒适度。然而，以前的 He 磁强计显示出的噪声超过 200 fT/Hz，带宽为 300 Hz。我们在这里描述了一种改进的磁强计，其灵敏度优于 50 fT/Hz，接近光子散粒噪声极限，带宽为 2 kHz。与其他零场原子磁强计一样，这些磁强计可以在闭环架构中运行，达到数百个 nT 的动态范围。一个由 4 个磁强计组成的小阵列在闭环中运行，已经成功地校正了串扰。
