Dynamics of cooperative emissions in a cascade three-level molecular system driven by an ultrashort laser pulse

This paper investigates the dynamics of cooperative emissions in acascade three-level system driven by an ultrashort laser pulse bysolving numerically the full-wave Maxwell--Bloch equations. The 4,4$'$-bis(dimethylamino) stilbene molecule is used as the modelmolecule because of its strong two-photon absorption property. Thetwo-colour cooperative emissions are studied as functions ofmolecular number density and dephasing rate of the dipole coherence.The propagation effects on the evolution of the cooperativeradiations are also taken into account. The cooperative radiationsare enhanced for large number density of the molecule, while thefast dephasing of the dipole coherence reduces the intensity of thecooperative radiations and delays the emission times or eveninhibits the formation of the emissions. The delay time of theradiation decreases with the increase of the molecular numberdensity and the propagation distance.