自旋交换碰撞导致的原子相干性破坏（弛豫）是影响地磁勘探中使用的原子磁力仪灵敏度的重要因素，特别是在高温、非弱磁的情况下为主要影响因素。本文使用光致压窄（light narrowing）效应对其进行限制，通过调节泵浦光的光强与波长来提高原子的极化率，抑制自旋交换碰撞弛豫带来的磁共振线宽的展宽，进而提高磁力仪灵敏度。通过建立钾原子磁力仪理论模型，针对多种变量进行优化，分析其中的不同弛豫过程以及光致压窄效应对原子磁力仪灵敏度的提升。计算结果表明，在一般条件下对于2 cm×2 cm×2 cm的原子气室，温度为200 ℃时，将泵浦率由0 Hz提升到620 Hz，可以将磁共振响应线宽由25 kHz压窄至312 Hz，此时有最优灵敏度为0.171 fT/Hz1/2。计算结果揭示了泵浦光导致的光致展宽和自旋交换碰撞弛豫消除两种机制的竞争关系，并优化了系统参数对磁力计灵敏度的影响。
We demonstrate the bandwidth enhancement of an all-optical spin-exchange relaxation-free (SERF) magnetometer based on amplitude-modulated (AM) light. Alkali metal atoms are modulated directly by the pump beam instead of the modulation field or radio frequency field. The first harmonic demodulation of an AM SERF magnetometer with a modulation intensity of 15 kHz results in a high bandwidth of over 11 kHz with a sensitivity of 20 fT/Hz1/2 at 30 Hz and 60 fT/Hz1/2 at 10 kHz. Meanwhile, the AM SERF magnetometer with DC demodulation presents the same sensitivity as a traditional DC SERF magnetometer (6 fT/Hz1/2 at 30 Hz). The presented technique for modulating the amplitude of the pump beam allows AM SERF magnetometers to enter the domain of high-bandwidth magnetometers and opens the door to many areas that are inaccessible to conventional magnetometers.
提出一种基于同位素原子饱和吸收谱稳频的拉曼激光方案，并应用于原子干涉仪激光系统的小型化。该方案使用同位素原子吸收泡代替现有拉曼光方案中的移频或调制光学器件，以实现拉曼激光的稳频和失谐，使光路和电路同时简化。针对85Rb原子干涉仪，87Rb原子D2线的饱和吸收谱被用于对拉曼激光进行稳频，稳频后的拉曼激光红失谐在GHz量级，线宽约为80 kHz。将该拉曼激光用于原子干涉仪获得了对比度为20%的干涉条纹，重力测量的灵敏度为345 μGal/Hz1/2。连续24 h重力测量数据的阿伦方差显示原子干涉仪的分辨率约为2×10-8g@7 500 s。该拉曼激光的频率噪声引起的单次重力测量噪声优于1 μGal，完全可以满足μGal量级的重力测量需求。该拉曼激光方案有助于推动原子干涉仪激光系统的小型化、轻量化和实用化。
A single-beam atomic magnetometer being operated near zero-field and measuring three-axis fields simultaneously is demonstrated. We produce a rotating field on the x-0-y plane with the frequency of 90 Hz and a modulation field in the z axis at 130 Hz. The rotating field enables a nonzero z axis output when the transverse fields are zeroed using feedback systems. Based on the phase difference of π/2, x and y axes fields can be measured using one lock-in amplifier. Magnetic field sensitivities of 300 fT/Hz1∕2 in x and y axes and 3 pT/Hz1∕2 in the z axis are achieved.
Compact atomic magnetometer has become an important approach for noise measurement of magnetic shielding systems as well as biomagnetic measurement. In this study, we propose a novel method that enables time-shard triaxial magnetic field measurements in near-zero magnetic field through a compact high-performance atomic magnetometer with femtotesla sensitivity. With pump–probe orthogonal configuration, the magnetometer can be operated without optical and magnetic modulation. They-axis magnetic field measurement was realized in zero field, whereas thex- andz- axes magnetic fields were measured by the cross-application of the bias magnetic fields operating in near-zero field. The maximum response amplitude and sensitivity with bandwidths of 46.8 Hz (x- axis), 10.5 Hz (y-axis), and 10.9 Hz (z-axis) are achieved under bias magnetic fields of
Bz−offset=8nT and
Bx−offset=2nT. The bandwidth alongx- axis was extended to 232 Hz under
Bz−offset=32nT, which can further be improved by increasing
Bz−offset. The linear interval of measurable magnetic field are between −11.7 to +11.7 nT (x- axis), −0.8 to +0.8 nT (y-axis), and −28.2 to +28.2 nT (z-axis). Forx- andz-axes, the measurable interval can further be improved by increasing
Bz−offsetand
Bx−offset, respectively. The triaxial sensitivities achieved through our method reached 3.1 ± 0.3 fT/Hz1/2(x- axis), 2.0 ± 0.1 fT/Hz1/2(y- axis), and 6.0 ± 0.5 fT/Hz1/2(z- axis). This system is measured in a low-noise ferrite magnetic shield to ensure extra-low magnetic noise condition. Furthermore, the non-modulation triaxial vector operation demonstrated in this study is advantageous for reducing interference and spin-exchange relaxation caused by magnetic field modulation.
基于铯原子系综四波混频过程制备的强度差压缩态光场具有波长与铯原子跃迁线匹配和空间多模的优势，在量子信息领域具有重要应用。然而，通过铯原子四波混频过程制备高压缩度的压缩态光场通常需要较高的泵浦光功率和原子池温度，这限制了其应用。本研究结合六镜环形光学谐振腔和铯原子系综，使泵浦光在光学谐振腔内实现单共振，同时让探针光和共轭光单次穿过光学谐振腔，有效提高了泵浦光的利用率，进而实现了腔增强的铯原子四波混频过程，从而显著降低了其对泵浦光功率和原子池温度的要求。实验结果表明，当获得的强度差压缩度为-6 dB时，相比于无腔四波混频过程，腔增强四波混频过程所需的泵浦光功率由600 mW降低至340 mW，并且原子池温度由109 ℃降低至98 ℃。研究结果为发展低功耗、空间多模量子光源提供了新方案，对于促进原子系综四波混频过程的应用具有重要意义。