Magneto-optical double resonance driven by fictitious fields.

Light-shift caused by the interaction between atoms and detuned light can be equivalent to the phenomena that atoms are coupled to an external magnetic or electric field. A fictitious magnetic or electric field is used to describe the effect of light-shift. Whether fictitious magnetic or electric field should be used depends on the polarization state of the detuned light. The fictitious fields can shift Zeeman sublevels and excite transitions between different sublevels. We study the magneto-optical double resonance of optically polarized ⁴He atoms driven by the detuned light with either circular or linear polarization states, model the light-shift with effective Hamiltonian, and the polarized ⁴He metastable state with density matrix calculations. Our proposed theoretical explanations based on the fictitious fields show good agreement with experimental results, especially for amplitude and frequency shifts of the signals at Larmor frequency and double Larmor frequency driven by the fictitious electric field.