Sub-Doppler laser cooling on combined optical transitions

We study the laser cooling process in a complex lambda system in the presence of force-assisted bichromatic velocity-selective coherent population trapping. Our theoretical model includes atomic transitions based on two ground states, Fg=1 and Fg'=3, and one excited state, Fe=2, excited by a bichromatic laser field tuned in resonance with the Fg=1→Fe=2 and Fg'=3→Fe=2 transitions. The analyzed optical scheme may be useful for alternative transverse cooling in experiments with group III atoms (Al, Ga, In)