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CONTROLE DE LA PROPAGATION D'IMPULSIONS ULTRACOURTES. EFFETS DE DELACEMENTS LUMINEUX

Jean-Christophe Delagnes 1
1 Femto (LCAR)
LCAR - Laboratoire Collisions Agrégats Réactivité
Abstract : The topic of this work deals with theoretical and experimental study
of the control of ultrashort pulse coherent propagation in optically
dense medium. First, we describe the basics of propagation
phenomena. The optical thickness characterizes the importance of the
temporal distortion of the pulse profile. As prisms or gratings
compressors are used to cancel the dispersion of transparent medium,
we show that a high resolution pulse shaper can compensate for the
resonant dispersion. Secondly, we study the idea of using a strong
driving pulse, to control the transient properties of a weak
resonant pulse simultaneously propagating in the medium. The strong
field induces transient modifications in the medium, that modify via
radiation the electric field of the weak resonant propagating pulse.
In a three level ladder system, modulations appear on the intensity
profile, and reveal the light shift induced (off resonance) on the
two upper levels. Their characteristic duration is shorter than the
initial pulse duration : new components thus appear on the
transmitted spectrum. These oscillations are the consequence of the
beating between the incident and the radiated field whose frequency
sweeps in time, following the light shift. In the bichromatic
excitation of a two level system, two spatial configurations give
access to different information. Besides the previous phenomena
appearing in non collinear geometry, the non adiabatic transitions
induced by the driving field are also involved in collinear
interaction. A weak pulse can be used as a very sensitive probe to
these effects. Finally, we study a configuration where two
orthogonally polarized pulses, excite resonantly a four level system
degenerated two by two. With the strong field mixing the states, the
emission and absorption path of the weak field have similar
contribution. The two paths interfere thus modulating the
transmitted pulse energy. The interplay of the light shift and the
interference, enables us to control the gain and the pulse temporal
shape as well.
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Submitted on : Saturday, June 17, 2006 - 12:57:02 PM
Last modification on : Friday, February 28, 2020 - 1:52:03 PM
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  • HAL Id : tel-00080477, version 1

Citation

Jean-Christophe Delagnes. CONTROLE DE LA PROPAGATION D'IMPULSIONS ULTRACOURTES. EFFETS DE DELACEMENTS LUMINEUX. Physique Atomique [physics.atom-ph]. Université Paul Sabatier - Toulouse III, 2005. Français. ⟨tel-00080477⟩

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