Polarization dependence of magnetic resonances in rubidium vapor using amplitude-modulated light: Theoretical and experimental investigations

We report on experimental and theoretical investigations on the polarization dependence of magnetic resonance generated by synchronous optical pumping. Narrow linewidth magnetic resonances are obtained experimentally by using a rubidium vapor cell with antirelaxation coating. We studied the effect of light ellipticity on the amplitudes and widths of magnetic resonances when light modulation frequency matches with 2{\Omega}L (alignment) and {\Omega}L (orientation) in a Bell-Bloom interaction geometry, with {\Omega}L corresponding to the Larmor frequency. Both 2{\Omega}L and {\Omega}L resonance amplitudes showed a strong dependence on the light ellipticity. In addition, we also show that the duty cycle of light modulation can control the rate of variation of 2{\Omega}L and {\Omega}L resonance amplitudes. This can find potential usage in applications that require in situ measurement of light ellipticity. We also studied the dependence of 2{\Omega}L and {\Omega}L resonance amplitudes on the polarization angle by using a linearly polarized light. We observed that these amplitudes oscillate periodically with the polarization angle. This oscillatory behavior is sensitive to the tilt in magnetic field orientation from the polarization plane. Such a property could be used to realize a vector magnetometer using synchronous optical pumping. A density matrix based theoretical model is developed to simulate the resonance spectrum for different light polarizations. The model accurately reproduces the above-mentioned experimental observations.