Electron spin polarization gradient suppression based on light polarization self-compensation

Optical pumping technology stands as a cornerstone for various quantum sensors. For a high-density atomic ensemble, the pump beam experiences significant attenuation due to absorption, which in turn induces a spin polarization gradient. This study introduces a novel polarization gradient suppression technique by means of self-compensating polarized light. By innovatively establishing a polarization state variation model of the pump beam, we find that the circular polarization degree of the elliptically polarized pump beam dynamically increases during absorption in the atomic ensemble. Its core mechanism stems from the polarization-selective absorption of polarized alkali metal atoms, and this intrinsic polarization variation serves as a compensation for the attenuation of pump light intensity, resulting in a 64% reduction in the polarization gradient. Experiments on the spin-exchange relaxation-free (SERF) co-magnetometer show that, compared with conventional circularly polarized pumping, the proposed method further increases the nuclear transverse relaxation time by 42.7 s, improves the rotation measurement sensitivity by 30%, and enhances the Allan deviation performance by 35%. It is applicable to a wide range of high-density miniaturized atomic sensors using optical pumping technology, without the need for additional compensation units.