Enhanced optical pumping using mutually orthogonal magnetic fields for quantum sensing

The atomic population trapped in irrelevant atomic states is a limiting factor for sensors based on laser-atom interaction. Using a bi-chromatic light field along with a specific combination of magnetic fields, we show a significant increase in the amplitude (i.e., more than seven times) of a two-photon coherent population trapping (CPT) resonance, which can be effectively used for atomic magnetometry. This increase in amplitude can be explained through enhanced optical pumping via the transfer of population to the relevant Zeeman states. Our experimental observations are consistent with the theoretical calculations carried out for a realistic three-level atomic system using density matrix formalism. We further discuss the optimum condition for enhanced optical pumping by adjusting the ground-state decoherence rate. Enhanced optical pumping through the manipulation of the magnetic field is quite important and is of great interest in the field of quantum technology.