Interference at quantum transitions: lasing without inversion and resonant four-wave mixing in strong fields at Doppler-broadened transitions

摘要

An influence of nonlinear interference processes at quantum transitions understrong resonance electromagnetic fields on absorption, amplification andrefractive indices as well as on four-wave mixing processes is investigated.Doppler broadening of the coupled transitions, incoherent excitation,relaxation processes, as well as power saturation processes associated with thecoupled levels are taken into account. Both closed (ground state is involved)and open (only excited states are involved) energy level configurations areconsidered. Common expressions are obtained which allow one to analyze theoptical characteristics (including gain without inversion and enhancedrefractive index at vanishing absorption) for various V, Lambda and Hconfigurations of interfering transitions by a simple substitution ofparameters. Similar expressions for resonant four-wave mixing in Ramanconfigurations are derived too. Crucial role of Doppler broadening is shown.The theory is applied to numerical analysis of some recent and potentialexperiments.