Lossless formation of electromagnetically induced transparency in sodium atoms

In this paper we propose a simple method for eliminating the population losses of MC resonances by involving all atoms of the Na ground state in the formation of the narrow coherent resonances observed in the fluorescence when scanning around zero value the applied magnetic field. As a result, dark resonances with a contrast up to 100% have been observed. Results are obtained in two different experimental configurations: using laser excitation of linear and circular polarization, leading to different population redistribution among Zeeman and hf levels. Theoretical analysis of the results is also presented. It is shown that at certain conditions complete optical pumping of atoms to levels F_g=2, m_Fg=2 or m_Fg=-2 can be achieved, which means complete orientation of the atoms.