Excitation by short light pulses of a two-level system with relaxing excited states

A. Zh. Muradyan, L. Petrosyan

Valeriy, Alexandrovich, Astapenko +3 more

Jean‐Claude Diels

Propagation of short ($\ensuremath{\lesssim}{T}_{2}$, where ${T}_{2}$ is the phase relaxation time) light pulses through absorbing media consisting of two ensembles of two-level systems of slightly different transition frequency is considered here. It is shown that one group of absorbers can be totally excited (inverted) while the other is returned to ground state. The effect of inhomogeneous broadening is illustrated by examples of propagation (numerical simulation) of properly shaped pulses through media having a linewidth equal to 1/5 of the frequency separation between the two transitions. The initial proportion of the two-level mixture is: 5% of the element to be excited, 95% of the element to be kept in ground state. The selective excitation capabilities of a Gaussian pulse and a zero-area pulse are compared.

Joachım Herrmann, J. Wienecke, B. Wilhelmi

A. D. Wilson‐Gordon, Harry Friedmann

We predict that the four-wave mixing (FWM) excitation spectrum for a two-level system becomes extremely asymmetrical when steady-state excitation is replaced by pulsed excitation, using temporally nonoverlapping probe and pump pulses. We also show that when a resonant probe pulse precedes the detuned pump pulse, the FWM signal may become more intense than when the pulses overlap. These effects are attributed to free-induction decay (FID): the coherence induced in the two-level system by a short resonant probe pulse survives the pulse (FID) and replaces it in producing a strong nonlinear signal on interaction with the strong pump pulse. Moreover, by plotting the FWM signal intensity as a function of the delay between the probe and pump pulses, an efficient method is proposed for determining short transverse relaxation times or fast chemical reaction rates.

Pankaj Kumar Jha, Hichem Eleuch, Fabio Grazioso