We report on experimental and theoretical investigations of the polarization dependence of magnetic resonance generated by synchronous optical pumping. Magnetic resonances with narrow linewidth are generated experimentally using a rubidium vapor cell with octadecyltrichlorosilane antirelaxation coating on inner walls. We studied the effect of light ellipticity on the amplitudes and widths of magnetic resonances by matching the light modulation frequency with $2{\mathrm{\ensuremath{\Omega}}}_{L}$ (alignment) and ${\mathrm{\ensuremath{\Omega}}}_{L}$ (orientation) in a Bell-Bloom interaction geometry, where ${\mathrm{\ensuremath{\Omega}}}_{L}$ corresponds to the Larmor frequency. Both $2{\mathrm{\ensuremath{\Omega}}}_{L}$ and ${\mathrm{\ensuremath{\Omega}}}_{L}$ resonance amplitudes showed a strong dependence on the light ellipticity. In addition, we showed that the duty cycle of light modulation changes the slope of amplitude variations in $2{\mathrm{\ensuremath{\Omega}}}_{L}$ and ${\mathrm{\ensuremath{\Omega}}}_{L}$ resonances with light ellipticity. As a potential application, we showed that the difference between $2{\mathrm{\ensuremath{\Omega}}}_{L}$ and ${\mathrm{\ensuremath{\Omega}}}_{L}$ resonance amplitudes can be used for in situ measurement of light ellipticity. We also studied the dependence of $2{\mathrm{\ensuremath{\Omega}}}_{L}$ and ${\mathrm{\ensuremath{\Omega}}}_{L}$ resonance amplitudes on the polarization angle of linearly polarized light. These amplitudes oscillate periodically with the polarization angle. We found this oscillatory behavior to be sensitive to the tilt in magnetic field direction from the polarization plane. Such a property could be used to realize a vector magnetometer. A density matrix based theoretical model is developed to simulate the magnetic resonance spectrum for different light polarizations. Our theoretical model accurately reproduces the above-mentioned experimental observations.
The effect of incident light field ellipticity on the electromagnetically induced absorption (EIA) and electromagnetically induced transparency (EIT) resonances has been studied experimentally and computationally in Hanle configuration with longitudinal and transverse magnetic fields. We identify the Zeeman coherences that influence the resonance profile and study the role of coherence-transfer from excited to ground state via spontaneous emission as a function of ellipticity for the ${F}_{g}=2\ensuremath{\rightarrow}{F}_{e}=3$ transition of
87Rb. The EIT resonance observed with the light field locked on the ${F}_{g}=1\ensuremath{\rightarrow}{F}_{e}=2$ transition of
87Rb is an influence of the nearby ${F}_{g}=1\ensuremath{\rightarrow}{F}_{e}=0$ closed and ${F}_{g}=1\ensuremath{\rightarrow}{F}_{e}=1$ open transitions. With increase in ellipticity the observed EIA and EIT resonances diminish in amplitude for a longitudinal magnetic field and are enhanced for a transverse magnetic field. We computationally account for these observations and discuss the factors that influence the EIA and EIT resonance amplitudes as a function of ellipticity and show that for a transverse field scan the ellipticity dependence of the EIA resonance amplitude can be accounted for without invoking the Doppler effect unlike for a longitudinal field scan. We also show that the maximum in the EIA resonance amplitude obtained for nonzero ellipticities with a longitudinal magnetic field depends on the closedness of the atomic system.
Coherent population trapping (CPT) resonances on the degenerate two-level system of the (Fg=2→Fe=1) transition of the 87Rb D1 line were investigated in an uncoated vacuum cell by means of level-crossing type experiments-sweeping a magnetic field around zero value and using a single laser beam. The two-photon resonance manifests itself as fluorescence canceling when the system of levels is degenerate (at zero point of magnetic field). The influence of weak transverse magnetic fields on the amplitude and width of the resonance was investigated. The CPT resonances were observed with linear, circular and elliptical polarized laser light. Transverse magnetic field widens the resonances obtained by linear and circular polarization but splits the resonance created by slightly elliptically polarized laser light. The dependence of this splitting on the elliptical ratio and experimental geometry were investigated. Due to its narrow width and sensitivity to low magnetic fields (< 1 G) this resonance is very promising for small magnetic field measurement.