采用反抽运光改善光泵铷原子磁强计的灵敏度

Improving the sensitivity of an optically pumped rubidium atomic magnetometer by using of a repumping laser beam

在光泵原子磁强计的实验装置中,窄线宽及高信噪比的磁共振信号是实现高灵敏度磁强计的充要条件.本文的实验中利用795 nm波长窄线宽单频连续极化光(同时也是探测光)对比研究了不同类型铷原子气室、不同温度下典型的磁共振信号,在镀石蜡的铷原子气室中获得最优化的磁共振信号.通过引入铷原子D2线780 nm波长窄线宽单频连续反抽运光,研究了激光功率对磁共振信号信噪比和线宽的影响.实验表明,780 nm波长窄线宽单频连续反抽运光的引入使得铷-85原子磁共振信号的信号幅值有明显提高并且线宽没有明显展宽.引入780 nm波长窄线宽单频连续反抽运光后,闭环锁定的铷-85原子磁强计在约1.2 kHz频率带宽范围内灵敏度约为26.4 pT/Hz^(1/2),相比仅有795 nm波长窄线宽单频连续极化光(同时也是探测光)存在时提高了近1个数量级.同时本实验利用增强后的铷原子磁共振信号对一种商用的磁通门磁强计在弱磁场测量时的准确度和偏差进行了校准.

For the experimental implementation of an optically pumped atomic magnetometer,the magnetic resonance signal with a narrow linewidth and a high signal-to-noise ratio(SNR)is required for achieving a high sensitivity.Using 795-nm laser as both the pumping and the probe laser,we compare the magnetic resonance signals from different rubidium atomic vapor cells and investigate the variations of magnetic resonance signals with temperature.Optimized magnetic resonance signal is achieved with a paraffin-coated rubidium atomic vapor cell.Then the 780-nm laser at rubidium D2 line is introduced as a repumping laser,and we explore the changes of linewidth and SNR of the magnetic resonance signal under different power of the pumping laser and the repumping laser.Owing to the 780-nm repumping laser beam,the signal amplitude of rubidium-85 magnetic resonance signal is improved remarkably because more rubidium-85 atoms are spin-polarized by the 795-nm pumping laser beam.At the same time,the linewidth of rubidium-85 magnetic resonance signal is roughly not broadened anymore.We realize a closed-loop optically pumped rubidium-85 atomic magnetometer with a bandwidth of~1.2 kHz,and the sensitivity is calibrated to be~245.5 pT/Hz^(1/2) only with the 795-nm pumping laser beam.Owing to the employment of the 780-nm repumping laser beam,the sensitivity is improved to be~26.4 pT/Hz^(1/2) which is improved roughly by one order of magnitude.We also calibrate the measurement accuracy and deviation of a commercial fluxgate magnetometer by using the enhanced rubidium magnetic resonance signal.