arXiv:1311.4187 · Physical Review A
Lasing and high-temperature phase transitions in atomic systems with dressed-state polaritons
Igor Yu. Chestnov, A. P. Alodjants, Sergei M Arakelyan
Abstract
We consider the fundamental problem of high-temperature phase transitions in the system of high-density two-level atoms off-resonantly interacting with a pump field in the presence of optical collisions (OCs) and placed in the cavity. OCs are considered in the framework of thermalization of atomic dressed-state (DS) population. For the case of a strong atom-field coupling condition, we analyze the problem of a thermodynamically equilibrium superradiant phase transition for the order parameter representing a real amplitude of cavity mode and taking place as a result of the atomic DSs thermalization process. Such a transition is also connected with condensed (coherent) properties of low branch DS polaritons occurring in the cavity. For describing nonequilibrium phase transitions we derive Maxwell-Bloch--like equations which account for cavity decay rate, collisional decay rate, and spontaneous emission. Various aspects of transitions to laser field formation by using atomic DS levels for both positive and negative detuning of a pump field from atomic transition frequency are studied in detail. It is revealed that for positive atom-light detuning DS lasing can be obtained in the presence of quasiequilibrium DS population that corresponds to a true two-level atomic system with the inversion in a nonresonant limit.