Liwei Jiang

Light intensity stabilization based on the second harmonic of the photoelastic modulator detection in the atomic magnetometer.

The fluctuations of the probe light intensity seriously affect the performance of the sensitive atomic magnetometer. Here we propose a novel method for the intensity stabilization based on the second harmonic component of the photoelastic modulator (PEM) detection in the atomic magnetometer. The method not only could be used to eliminate the intensity fluctuations of the laser source, but also remove the fluctuations from the optical components caused by the environment. A relative fluctuation of the light intensity of 0.035% was achieved and the corresponding fluctuation of the output signal of the atomic magnetometer has decreased about two orders of magnitude from 4.06% to 0.041%. As the scheme proposed here only contains optical devices and does not require additional feedback controlled equipments, it is especially suitable for the integration of the atomic magnetometer.

Spin-exchange collision mixing of the K and Rb ac Stark shifts

In a hybrid pumping alkali vapor cell that both K and Rb are filled, K atom spins are optically pumped by laser and Rb atom spins are polarized by the K spins through spin exchange. We find that the AC Stark shift of the Rb atoms is composed of not only the AC Stark shift of the Rb atoms caused by the far off resonant pumping laser which is tuned to the K absorption lines, but also the AC Stark shift of the K atom spins. The mixing of the light shifts through fast spin exchange between K and Rb atoms are studied in this paper and we demonstrate a K-Rb-21Ne co-magnetometer in which the AC Stark shift of the Rb atoms are reduced by the collision mixing.

A parametrically modulated dual-axis atomic spin gyroscope

We describe a dual-axis atomic spin gyroscope based on an alkali metal-noble gas comagnetometer. Alkali metal vapor is optically pumped, and then the noble gas is hyperpolarized along the z axis. When sensing a transverse rotation, the polarized noble gas will be induced to precess and produce an effective magnetic field in the x – y plane for alkali metals to precess under. Operating in the spin-exchange relaxation-free regime, alkali atoms are modulated by the z axis magnetic field and serve as an integrated in-situ dual-axis magnetometer to detect the gyroscopic precession in the x and y axes simultaneously, using a single probe beam. By using the parametric modulation technique, the low frequency drift is effectively suppressed and a bias instability of less than 0.05 deg/h has been achieved in our dual-axis atomic spin gyroscope.

Common-mode noise reduction in an atomic spin gyroscope using optical differential detection

Optical rotation of linearly polarized light is used to measure atom spin precession in an atomic spin gyroscope (ASG). However, the common-mode noise in the polarization measurement seriously affects the performance of the sensitive ASG. Here we propose an optical differential detection method based on the photoelastic polarization modulation, which could effectively eliminate the light power fluctuation of the laser source and optical elements, while removing the polarization noise and the residual birefringence. The feasibility and efficiency of this method have been verified experimentally. The rotation sensitivity of the ASG is an order of magnitude better, and the long-time stability is significantly improved. In addition, this method is easier to implement because noise sources do not need to be strictly distinguished.

Rotation sensing decoupling of a dual-axis K-Rb- 21 Ne atomic comagnetometer

A dual-axis atomic comagnetometer can sense the angular rotation of two measurement axes simultaneously and independently. However, there is a cross-talk coupling effect between the two axes because of the residual magnetic field and the light shift arising from the pumping laser. Here, we propose a scheme to eliminate the rotation coupling of dual-axis K-Rb-N21e atomic comagnetometers. The residual magnetic field can be effectively removed by controlling the comagnetometer at the magnetic compensation point and the magnetic shielding layer. The light shift could be eliminated by using the K atom light shift to counteract the Rb atom light shift, in which the light shift of K atoms was optimized to the decoupling point by finely adjusting the pumping laser wavelength of the K D1 line. The feasibility and efficiency of this decoupling scheme have been experimentally verified. The output response of the coupling axis is reduced by two orders of magnitude compared to the sensitive axis. This scheme can also be applied to any atomic comagnetometer with hybrid optical pumping that experiences cross-talk coupling.

Method for simultaneously calibrating peak retardation and static retardation of a photoelastic modulator

A method for simultaneously calibrating the peak retardation and static retardation of a photoelastic modulator (PEM) is proposed. By optimizing the polarization modulation system, the normalized fundamental frequency components of the modulation signals are obtained to calculate the peak retardation and static retardation of the PEM. The calibration result is immune to fluctuations of the incident light intensity and can be used to correct the deviation of the photoelastic modulation detection results. In our experiments, the average deviation between measured peak retardations and corresponding set values is 0.0339 rad. The standard deviation between the measured static retardations and the average measured value is 0.0003 rad. The calibration method has a high sensitivity, since the large gradient of the first-order Bessel function when the peak retardation is less than 1 rad. The experimental results are consistent with the theoretical analysis.