在无自旋交换弛豫原子磁强计中, 需要检测极小的旋光角度。基于光弹调制器的偏振调制技术由于其较低的噪声和长时间的稳定性在各种检测方法中是优选的。但光弹调制器的输出信号里包含有大量噪声和高次谐波, 严重影响了原子磁强计的性能。针对以上问题分析了基于光弹调制器的偏振调制技术的原理和待检测信号的特性, 并提出一种基于双通道数字锁相放大器的原子磁强计微弱信号检测方法。该方法简化锁相放大算法, 减小电路复杂度, 并能准确地同时检测一次谐波和二次谐波的幅值。理论分析和仿真结果表明, 该检测系统工作良好, 可以准确地检测微弱信号, 误差在0.1%以内。

In the spin exchange relaxation free (SERF) atomic magnetometer, it is necessary to detect an extreme small optical rotation angle. Among various methods for detecting the rotation angle, the polarization modulation technique based on a photoelastic modulator (PEM) is preferred because it features lower noise and better stability at long-time scales. However, the output signal of the photoelastic modulator contains much noise and high-order harmonics, which seriously affects the performance of the atomic magnetometer. The principle of polarization modulation technique based on photoelastic modulator and the characteristics of the detected signal were analyzed. And a dual channel digital lock-in amplifier to detect the weak signal from the atomic magnetometer was proposed. This method simplified the lock-in algorithm, reduced the complexity of the circuit and accurately detected the amplitudes of the first harmonic and the second harmonic. Theoretical analysis and simulation results show that the detection system works well and detects weak signals accurately, and the simulation error is less than 0.1%.