Level-degeneracy effects in resonant nonlinear phenomena: Three-level atomic model

Alexandre V. Kats, В. М. Конторович, A. V. Nikolaev

Govind Prasad Agrawal

The effect of level degeneracy on saturated absorption in a resonant medium is considered using a simple but realistic three-level system to model $J=1\ensuremath{\rightarrow}J=0$ atomic transition. Assuming homogeneous broadening and exact resonance, an analytic nonperturbative expression for the medium susceptibility is obtained and used to study propagation of an arbitrarily polarized optical field. Optical saturation affects considerably Zeeman-coherence-induced circular dichroism. The analysis may find application in high-resolution spectroscopy and other branches of nonlinear optics.

Christian Hicke

А. А. Черненко, Э. Г. Сапрыкин

The shapes of the saturated absorption resonances at transitions from the ground 1S0 atom state in a gas medium in the field of two unidirectional waves are investigated both analytically and numerically. It is shown for the first time that the spectra of nonlinear resonances are formed by processes in the two-and three-level V-schemes resulting from the degeneracy of the upper P transition state, are qualitatively different at the resonant transition and transitions to the more excited atom states. It is established that the physical causes for differences of these spectra are due to the different degree of branching of the radiation from the excited to the ground state (the degree of openness) of transition. The degree of openness of transition determines the amount of contributions of coherent processes to the resonance shapes both in the system of two levels (coherent population beats) and three levels (nonlinear interference effect).

R. R. Muryasov, A. L. Nefedov

W A McClean, S. Swain

Feneuille and Schweighofer (1975) have used a three-level model to discuss the observation of the Autler-Townes effect in a two-step resonance experiment. A numerical investigation is presented in which the effect of the neighbouring non-resonant hyperfine levels is taken into account. Firstly all the levels are treated as non-degenerate, and then degeneracy is allowed for. It is found that both the inclusion of the neighbouring states and allowance for their degeneracy cause a large change in the expected upper-state population, especially at high light intensities. It is concluded that the resonant three-level model is a poor model in this situation.