SUBRECOIL LASER COOLING BY VELOCITY-SELECTIVE COHERENT POPULATION TRAPPING IN CASCADE SYSTEMS

A theoretical analysis of laser cooling of atoms by velocity-selective coherent population trapping in a three-level cascade system is presented. We show that the temperature of the cooled atoms can be well below the value determined by the recoil energy. Conditions For coherent population trapping in the cascade scheme to be established are derived and, different implementations of cascade schemes are discussed. The analysis of laser cooling dynamics is performed with both full quantum and quasiclassical (for translational motion of atoms) approaches. We study the temporal evolution of the atomic momentum distribution and the efficiency of the cooling method considered. The analytical solution for the atomic density matrix is obtained in the limit of large interaction time and small kinetic momentum of the atom.