Three-level atom interferometer with bichromatic laser fields

We have developed a three-level atom interferometer using three-level atoms coupled with bichromatic fields in order to investigate the phase information between two excited states. First, we presented a theoretical description of the interaction of three-level atoms with bichromatic fields based on single-transition operators. Using the time evolution of a wave function, the equations of the interference fringes and the visibility were derived and calculated for several types of the three-level atom interferometers with bichromatic fields. Optimum excitation conditions were evaluated. Next, several types of three-level atom interferometers were demonstrated experimentally using a thermal calcium atomic beam with two Zeeman substates of m=1 and m=-1 in the long-lived excited state coupled with bichromatic resonant fields between the ground state and the excited states. The behaviors of the interference fringes were compared among them along with the calculated results. The three-level atom interferometer excited by two bichromatic laser beams separated in space was found to produce the largest visibility among them when the excitation power of each frequency component was the same.