The Dual Frequency Anisotropic Magneto-Optical Trap

The cloud of cold atoms produced by a Magneto-Optical Trap is known to exhibit instabilities. We examine in this paper in which limits it could be possible to realize an experimental trap similar to the configurations studied theoretically, i.e. mainly traps where one direction is privileged. We study the static behavior of an anisotropic trap, where anisotropy results essentially from the use of two different laser frequencies for the arms of the trap. Such a trap has very surprising behaviors, in particular the cloud disappears for some laser frequencies, while it exists for smaller and larger frequencies. A model is build to explain these behaviors. We show in particular that, to reproduce the experimental observations, the model has to take into account the cross saturation effects. Moreover, the couplings between the different directions cannot be neglected

Phase-space description of the magneto-optical trap

An exhaustive kinetic model for the atoms in a 1D Magneto-Optical Trap is derived, without any approximations. It is shown that the atomic density is described by a Vlasov-Fokker-Planck equation, coupled with two simple differential equations describing the trap beam propagation. The analogy of such a system with plasmas is discussed. This set of equations is then simplified through some approximations, and it is shown that corrective terms have to be added to the models usually used in this context

Isotropic Light vs Six-Beam Molasses for Doppler Cooling of Atoms From Background Vapor - Theoretical Comparison

We present a 3D theoretical comparison between the radiation-pressure forces exerted on an atom in an isotropic light cooling scheme and in a six-beam molasses. We demonstrate that, in the case of a background vapor where all the space directions of the atomic motion have to be considered, the mean cooling rate is equal in both configurations. Nevertheless, we also point out what mainly differentiates the two cooling techniques: the force component orthogonal to the atomic motion. If this transverse force is always null in the isotropic light case, it can exceed the radiation-pressure-force longitudinal component in the six-beam molasses configuration for high atomic velocities, hence reducing the velocity capture range.Comment: 10 pages, 8 figure

Collatinus & Eulexis : Latin & Greek Dictionaries in the Digital Ages.

International audienceCollatinus and Eulexis are free open-source programs, designed to lemmatize Latin or Greek texts and to open the digital dictionaries at the proper page. Collatinus has been originally developed by Yves Ouvrard for teaching. It allows to generate a complete lexical aid, with a short translation and the morphological analyses of the forms, for any text which can be given to the students. The program also allows to search for a word in the dictionaries, either in a digital form or as images. Eulexis is newer and is intended as Collatinus' counterpart for Greek texts, though it is based on different mechanisms. As any open-source program, Collatinus and Eulexis can be tuned to meet any particular problem. Both programs have an on-line version, developed with the help of Régis Robineau, webmaster of the Biblissima project. But, we consider here the features of the off-line versions

How to characterize the dynamics of cold atoms in non dissipative optical lattices?

We examine here the classical dynamics of cold atoms in square optical lattices, i.e. lattices obtained with two orthogonal stationary plane waves. Contrary to much of the past studies in this domain, the potential is here time independent and non dissipative. We show that, as a function of the experimental parameters, very different behaviors are obtained, both for the dynamics of atoms trapped inside individual sites, and for atoms travelling between sites: inside the sites, chaos may be a main regime or, on the contrary, may be negligible; outside the sites, chaos sometimes coexists with other regimes. We discuss what are the consequences of these differences on the macroscopic behavior of the atoms in the lattice, and we propose experimental measurements able to characterize these dynamics and to distinguish between the different cases

Dark Optical Lattice of Ring Traps for Cold Atoms

We propose a new geometry of optical lattice for cold atoms, namely a lattice made of a 1D stack of dark ring traps. It is obtained through the interference pattern of a standard Gaussian beam with a counter-propagating hollow beam obtained using a setup with two conical lenses. The traps of the resulting lattice are characterized by a high confinement and a filling rate much larger than unity, even if loaded with cold atoms from a MOT. We have implemented this system experimentally, and obtained a lattice of ring traps populated with typically 40 atoms per site with a life time of 30 ms. Applications in statistical physics, quantum computing and Bose-Einstein condensate dynamics are conceivable.Comment: 4 pages, submitted to PR