相干布居俘获(CPT)磁强计是基于原子系综中相干布居俘获相干叠加暗态使用全光学的方法对磁场进行测量,具有较高的精度。实验中使用注入锁定的方法得到频率差严格等于铯原子基态超精细分裂间距的两束大频差位相锁定的双色激光,观察到了铯原子气室中的CPT透射信号。给铯泡加入沿激光传播方向的纵向磁场,可观察到变宽或分裂的CPT信号,通过对分裂间距的测量便可得到待测磁场值。对于中等强度的磁场,可通过透射峰的裂距直接得到待测磁场值;弱磁场区域则可通过电流与磁场的对应关系得到。目前,实验中可测量nT量级的稳定磁场。

Coherent population trapping (CPT) magnetometer is based on coherent population trapping coherent dark states, using an all-optical method to measure the magnetic field with high accuracy. In our experiment, we used the method of injection locking to get the two color lasers with locked phase and large frequency difference, which equald to the hyperfine splitting of the cesium atoms′ ground states, and observed the CPT transmission signals. We added the longitudinal magnetic field which was along the laser propagation direction, and observed the widen CPT transmission peak and the splitting signals. For the magnetic field of medium intensity, we got the magnetic field value by measuring the splitting spacing, and for the weak region, the value could be obtained by the relation of current and magnetic field. In our experiment, we could measure the static field with several nT.