Light shift suppression in a CPT magnetometer using linear polarization and double frequency interrogation

Abstract

We demonstrate a suppression of the light shift in a Coherent-Population-Trapping (CPT) atomic magnetometer by using linearly polarized light and a differential measurement between magnetic resonances. The radio frequency that creates the optical sidebands for CPT quickly switches between two magnetic sensitive transitions and the magnetic field is extrapolated from the difference of the center frequencies of the magnetic resonances. Light shifts and common drifts like collisional shifts can be suppressed through careful choice of measured resonances and we show the light shift reduction by more than a factor of 20 compared to excitation with circular polarized light. Various limitations to the method are discussed.

Figures (5)

• Figure 1: Energy level diagram of the D1 line of $^{87}$Rb. The arrows represent the different $\Lambda$-schemes created with circularly (green) and linearly (blue) polarized light to excite the n=$\pm$ 2 transition.
• Figure 2: Experimental Setup. LPL: laser power lock, PD: photo-detector, fEOM: fiber electro-optical modulator, BS: beam splitter, P: polarizer, LTR: low temperature coefficient resistor, MCS: main current source, DMM: digital multimeter.
• Figure 3: CPT transitions excited by circular and linear polarizations.
• Figure 4: Differential light shift for circular (green) and linear polarization (blue).
• Figure 5: (a) Light shift dependence on the optical axis alignment (b) Light shift dependence on the $\hat{k}$ and $\hat{B_T}$ alignment.