477 research outputs found
V. Labeyrie, G. Fabres & D. Lachaise (ed.). — Insects-Plants. Proceedings of the 6th International Symposium on Insect-Plant Relationships (Pau 1986). W. Junk, Dordrecht, Nedherland, 1987
No full textPesson Paul. V. Labeyrie, G. Fabres & D. Lachaise (ed.). — Insects-Plants. Proceedings of the 6th International Symposium on Insect-Plant Relationships (Pau 1986). W. Junk, Dordrecht, Nedherland, 1987. In: Bulletin de la Société entomologique de France, volume 94 (1-2), juillet 1989. p. 2
Coherent light transport in a cold strontium cloud
No full textWe study light coherent transport in the weak localization regime using magneto-optically cooled strontium atoms. The coherent backscattering cone is measured in the four polarization channels using light resonant with a J(g)=0 to J(e)=1 transition of the strontium atom. We find an enhancement factor close to 2 in the helicity preserving channel, in agreement with theoretical predictions. This observation confirms the effect of internal structure as the key mechanism for the contrast reduction observed with a rubidium cold cloud [G.Labeyrie et al., Phys. Rev. Lett. 83, 5266 (1999)]. Experimental results are in good agreement with Monte Carlo simulations taking into account geometry effects
Nonlinear beam shaping by a cloud of cold Rb atoms
No full textFirst 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 F = 3 <-> F'= 4 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. <br/
A 90,000- 200,000 years marine tephra record of Italian volcanic activity in the Central Mediterranean Sea
No full text
Spatial patterns in nonlinear optics: nonlinear effects and patterns in a cold atomic cloud
No full textThe nonlinear interaction between an optical medium and an electro-magnetic field can induce gradients in the index of refraction distribution, leading to patterns or filamentation in the most diverse nonlinear materials: solids, anisotropic soft matter (liquid crystals), cells containing thermal vapors, etc. One common difficulty in interpreting the results of these experiments and in comparing them to models is that the details of the interaction in these media are very complex. Cold atomic systems have well known linear and nonlinear optical properties, as illustrated in experiments on four wave mixing, electro-magnetic induced transparency or slow light propagation. Such samples are thus an excellent candidate for improving the comparison between theory and experiments, but so far to our knowledge no investigations on patterns have been performed in such systems
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