Optically pumped magnetometers based on pseudo-random-bit-sequence phase modulation

A high-sensitivity atomic magnetometer based on broad linewidth laser pumping is demonstrated. The broad linewidth laser was obtained by broadening a narrow linewidth laser utilizing an external phase modulator driven by a pseudo-random-bit-sequence (PRBS) waveform. This ingenious optical pumping scheme can significantly enhance the signal response and suppress light shift noise, as well as can reduce the gradient of electron spin polarization and improve the stability of magnetometers. Compared with a narrow linewidth laser pumping scheme, the response of the magnetometer is increased by 56%, experimentally. The relative polarization gradient is reduced from 9.8%/cm to better than 4%/cm by setting PRBS with a bit rate of 16 GHz. This scheme can also be applied to many other fields such as noninvasive bio-magnetic imaging and atomic spin gyroscopes.