LAUSR

The optical rotation detection system (ORDS) based on photo-elastic modulator (PEM) has achieved ultrahigh sensitivities, and further sensitivity improvement requires higher light intensities. However, the relatively large phase retardations in PEM restrict intensity increasing with maximum power limit. In this article, we propose a novel reflecting modulation method in ORDS, which can realize high light intensity detection. In the reflecting system, after passing through the modulator, the light is reflected back to the modulator again. We calculate the Jones matrix of the reflecting modulation system and find that the matrix keeps unchanged except that the peak phase retardations decrease. Because of the smaller retardations, the acceptable incident light intensities increase, which can suppress the influence of the photon shot noise. In the experiment, we demonstrate that the peak phase retardation of a PEM decreases 3.8 times compared with the conventional system, and the probe sensitivity of the magnetometer is improved by about 1.4 times. The reflecting modulation system can be used in atomic magnetometers and co-magnetometers where small peak retardations are required.