https://doi.org/10.1140/epjd/e2003-00046-4
Nonlinear beam shaping by a cloud of cold Rb atoms
1
Laboratoire Ondes et Désordre (FRE-2302 CNRS) , 1361 route des Lucioles, 06560 Valbonne, France
2
Institut für Angewandte Physik, Westfälische
Wilhelms-Universität Münster, Corrensstraße 2/4, 48149 Münster, Germany
3
Optoelectronics Research Center, University of Southampton,
Southampton SO17 1BJ, UK
4
Institut Non Linéaire de Nice (UMR 6618 CNRS-UNSA) , 1361 route des Lucioles, 06560 Valbonne, France
Corresponding authors: a Guillaume.Labeyrie@inln.cnrs.fr - b t.ackemann@uni-muenster.de - c bgk@orc.soton.ac.uk - d pematze@zivlnx01.uni-muenster.de - e Gian-Luca.Lippi@inln.cnrs.fr - f Robin.Kaiser@inln.cnrs.fr
Received:
6
October
2002
Revised:
17
December
2002
Published online:
18
February
2003
First experimental investigations are reported on
nonlinear beam shaping due to the interaction between an
intense laser beam and a cloud of laser cooled rubidium atoms.
Resonant excitation of the hyperfine transition is
considered. The single-pass interaction through the cold vapor
causes an increase in the laser beam intensity in the forward
direction (zero transverse wavevector component) when observed in
Fourier space, for sufficiently high values of saturation. A qualitative
explanation of the observations based on
a two-level model for a resonantly excited transition
proves acceptable. The observations are compatible with an
interpretation based on nonlinear index-induced focusing of an incident beam
with curved wavefront, as is used in z-scan measurements. Simple
physical considerations allow us to deduce the conditions for the
observability of optical patterns in the beam transmitted by a
cold atomic cloud.
PACS: 42.65.Jx – Beam trapping, self-focussing, and thermal blooming / 32.80.Pj – Optical cooling of atoms; trapping / 42.65.Sf – Dynamics of nonlinear optical systems; optical instabilities, optical chaos and complexity, and optical spatio-temporal dynamics
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2003