Study of atomic coherence effects in sodium atom

Atomic coherence is generated when a multilevel atomic system is driven by bichromatic coherent fields. Specifically, population trapping results when one of the superposition states is decoupled from the driving fields. Mutual interaction between the two driving fields due to the atomic coherence effect is studied. Lasing without inversion is realized based on population trapping. Experiments with the sodium atom were designed and implemented. Density matrix analysis is employed to analyze the system.;Effect of a strong mutual influence between two trapping fields was observed in sodium cells. Unlike other experiments, absorption was directly monitored and the transient atomic coherence response was studied. Experimental results were compared with the theoretical predictions. Lasing without inversion was achieved in our system.