Nonadiabatic population inversion by laser frequency switching

Angelo Turrin

S.R. de Echaniz, Andrew D. Greentree, Alan V. Durrant +3 more

We have observed clear Rabi oscillations of a weak probe in a strongly driven three-level $\ensuremath{\Lambda}$ system in laser-cooled rubidium. When the coupling field is nonadiabatically switched on using a Pockels cell, transient probe gain without population inversion is obtained in the presence of uncoupled absorptions. Our results are supported by three-state computations.

F. A. Hashmi, M. A. Bouchène

A strong nonresonant, asymmetric ultrashort pulse drives an atomic transition and causes a complete population inversion because of a sudden nonadiabatic jump. This jump is probed in real time by propagating a weak ultrashort pulse in the system which is resonant on an adjacent transition. The probe at the exit of the medium presents an oscillatory structure with the nonadiabatic jump marked in time by the onset of oscillations. The nonadiabatic jump thus acts as a ``turn-on'' switch for the shaping of the probe.

Noriaki Tsukada

Razmik G. Unanyan, Леонід Петрович Яценко, Klaas Bergmann +1 more

V. N. Lugovoǐ, V. N. Streltsov

A theoretical analysis is made of the interaction between a two-level quantum-mechanical system and an electromagnetic field which is frequency- and amplitude-modulated. Attention is drawn to the fact that, subject to certain general assumptions, the usual methods for population inversion in such a system—(2 n + l)π pulses and adiabatic inversion methods—apply also if the pump field is of the wide-band type. Exact solutions are obtained for the nature of the time dependence of the instantaneous field frequency at which a population inversion occurs under nonadiabatic conditions.