Mean value and fluctuations of population of a two-level system excited by intense nonmonochromatic radiation

A. M. Bonch-Bruevich, S. G. Przhubelskii, V. A. Khodovoǐ +1 more

V. A. Khodovoǐ, V. V. Khromov

P. V. Elyutin

O. A. Kocharovskaia, Ia. I. Khanin, V. B. Tsaregradskii

R. Walser, Helmut Ritsch, P. Zoller +1 more

The nonlinear dynamics of a sample of two-level systems exposed to noisy laser light is investigated. As stochastic models we treat the chaotic field and the real Gaussian field. Based on the method of marginal characteristic functions, we deduce analytical solutions for the mean values and variances of the atomic populations in terms of matrix continued fractions. We find significantly enhanced on-resonance fluctuations for a real Gaussian field compared to a chaotic field of the same bandwidth and intensity. Furthermore, in contrast to phase-noise models, the fluctuations in the fluorescence intensity do not decrease to zero in the limit of slow fluctuations.

V. O. Chaltykyan, G. M. Grigorian, Y. Pashayan-Leroy

The problem of a two-level atom interacting with a nonmonochromatic radiation pulse is studied both with and without the resonant approximation. Using the time-dependent perturbation theory, the analytical expressions for transition probability of the atom are obtained. It is shown how, depending on the value of the field strength, the atom's excitation probability can be obtained with the needed accuracy. It is shown that the upper level population of the atom exhibits oscillations which are absent in the resonant approximation. It is shown that absorption probability and dipole moment spectrum are governed by interference between the spectral components of a non- monochromatic radiation involved in nonlinear interaction process. Spectral distribution symmetry with respect to the resonance frequency being destroyed, the atom can be excited even if there is no resonant component in the pulse spectrum.