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Journal de Physique IV (Proceedings)

Propagation of ultra-short pulses in resonant atomic systems : Observation and control

M. A. Bouchène, Jean-Christophe Delagnes, Marion Jacquey, Sébastien Bonhommeau, Peter V. Zahariev, Antoine Monmayrant, B. Chatel, B. Girard

Published Nov 1, 2004• 1 citation
Publisher

Abstract

\nWe discuss the possibility to control through two different experiments, the propagation effects that occur when an optically dense atomic medium is excited by ultra-short laser pulses. In the first experiment a direct compensation of the dispersion for one single pulse is obtained with a pulse-shaper device. In the second experiment, ce of ultra-short laser pulses is used. The dispersion effects are shown to depend crucially on the relative phase between the pulses.\n

DOI
10.1051/jp4:2004119003

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\nWe discuss the possibility to control through two different experiments, the propagation effects that occur when an optically dense atomic medium is excited by ultra-short laser pulses. In the first experiment a direct compensation of the dispersion for one single pulse is obtained with a pulse-shaper device. In the second experiment, ce of ultra-short laser pulses is used. The dispersion effects are shown to depend crucially on the relative phase between the pulses.\n
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In this book, we focus on the stochastic nature of pulses to achieve a more realistic description of ultra-short optical pulses affected by noise. In order to simulate ultra-short pulses, various stochastic pulse models were applied. The effects of pulse amplitude and phase fluctuations on its propagation in various linear and non-linear media were studied based on optical coherence theory. The response of the medium atoms to the applied stochastic pulses was investigated for the particular resonant case in which the pulse frequency nearly coincides with the atom resonance frequency. Analytical and numerical propagation methods were applied to explore evolutions of ultra-short stochastic pulses in the vicinity of optical resonance.
We present here a theoretical analysis of the propagation of a sequence of ultrashort pulses in an optically dense medium. The interaction is resonant and treated in the weak-field regime. Dispersion is dominant and induces important reshaping effects. We show that these effects depend crucially on the relative phase shift \ensuremath{\varphi} between the pulses. Compared to the case of a train of independent pulses (i.e., mutually incoherent), a pulse sequence with $\ensuremath{\varphi}=0$ is shown to be sensitive to dispersion for lower optical depths, whereas a pulse sequence with $\ensuremath{\varphi}=\ensuremath{\pi}$ is shown to be more robust.
We present an experiment in which an ultrashort pulse train propagates resonantly through anoptically dense vapor of atomic rubidium. The sequence obtained from a Fabry-Perot interferometer comprises nearly 10 regularly time-delayed and mode-locked pulses. We show that a sequence with phase shift phi = 0[2pi] between two successive pulses propagates with important temporal distortion, whereas a sequence with phi = pi[2pi] experiences few propagation effects, thus leading for the first time to our knowledge to the possibility of phase control of dispersion effects for an ultrashort pulse train.
Investigations of controlled modifications of dispersive properties of atomic media and of propagation of short laser pulses have recently become a dynamically developing field of theoretical and experimental researches. In this lecture a brief overview is presented of basic physical phenomena underlying modifications of a group velocity of a pulse propagating in an optically modified medium. In particular, the possibilities of slowing down this velocity to zero and of retrieving the stopped pulse are discussed.