Four-wave mixing in two-level atoms with stochastically modulated transition frequencies

We investigate nonlinear wave mixing in two-level atoms wherein, using a dr essed state formalism, it is shown that the signal arises as a consequence of quantum interference between relevant probability amplitudes for photon emission. We then report a theoretical study of the modifications that are induced in the four-wave mixing signals when the transition frequency of th e atoms is stochastically modulated. Such modulations, which arise from per turbations in the immediate environment of the atoms, are shown to cause si gnificant alterations in the nonlinear response of the atoms. We also descr ibe how one can, via an investigation of the four-wave mixing signal, diffe rentiate between Markov and non-Markov fluctuations in the transition frequ ency of the two-level system. The calculations rely on a recently developed Monte Carlo procedure that can be used to obtain exact solutions to a wide variety of spectroscopic problems, with minimal restrictions on atom, fiel d, and noise parameters. (C) 2001 American Institute of Physics.