Synchronous coherent population trapping and its magnetic spectral response in rubidium vapor

This paper reports experimental investigations of the spectral response of synchronous coherent population trapping (CPT) for magnetometry applications. Synchronous CPT is demonstrated using resonant two-photon excitation with a modulated bichromatic laser field in the $^{87}\mathrm{Rb} {D}_{1}$ manifold. Spectra containing multiple magnetic resonances are produced due to two-photon excitations created by various frequency components of the modulated beam. Theoretical modeling based on the atomic density-matrix equations is used to simulate the spectral response of synchronous CPT. Our results show potential advantages of synchronous CPT over synchronous optical pumping for magnetic field measurement. Magnetic resonance signals produced by synchronous CPT can be used in eliminating the dead-zone problem and also in determining the magnetic field direction.