Philippe Verkerk

Observation of instabilities due to mirrorless four-wave mixing oscillation in sodium

Abstract We report the observation of an instability when two counter-propagating pump beams interact with sodium atoms. The instability appears as a coherent emission around the pump beams axis. This oscillation has only been observed on the self-focusing side of the resonance in agreement with theory. The characteristics of the oscillation are very different from those of the usual conical emission.

Characterization and modelling of the hollow beam produced by a real conical lens

The properties of the hollow beam produced by a conical lens are studied in detail. In particular, the impact of a rounded vertex is examined. It is shown that it could lead to drastic changes in the transverse distribution of the hollow beam, determined by the ratio between the transverse size of the incident beam and the size of the blunt area. An adequate choice for this ratio allows us to either minimize the losses or optimize the distribution symmetry.

Dark optical lattice of ring traps for cold atoms

We propose an optical lattice for cold atoms made of a one-dimensional stack of dark ring traps. It is obtained through the interference pattern of a standard Gaussian beam with a counterpropagating 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 magneto-optical trap. We have implemented this system experimentally, and demonstrated its feasibility. Applications in statistical physics, quantum computing, and Bose-Einstein condensate dynamics are conceivable.

Spectral analysis of an injection-locked flash-lamp pumped dye-laser of ultranarrow linewidth

Abstract The intrinsic linewidth of an injection locked flash-lamp pumped dye-laser has been measured to be equal to 3.5 MHz. This result which is, to our knowledge, the best one reported for a pulsed laser is however larger than the Fourier limitation. The frequency shift between the cw master oscillator and the pulsed laser is equal to 7.5 ± 1.0 MHz under usual experimental conditions. The narrow linewidth and the good frequency reproducibility makes this light source very promising for applications in non-linear spectroscopy.

1S-3S and 1S-3D doppler-free two-photon transition in hydrogen and deuterium

Abstract We have observed the 1S-3S and 1S-3D Doppler-free two-photon transitions in hydrogen and deuterium using an intense monochromatic light source at 2050 a. The experiment is done in a cell in an afterglow discharge. We present the experimental results and discuss some possible future applications.

Phase-space description of the magneto-optical trap

Abstract. 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.

Synchronization in non dissipative optical lattices

AbstractThe dynamics of cold atoms in conservative optical lattices obviously depends on the geometry of the lattice. But very similar lattices may lead to deeply different dynamics. In a 2D optical lattice with a square mesh, it is expected that the coupling between the degrees of freedom leads to chaotic motions. However, in some conditions, chaos remains marginal. The aim of this paper is to understand the dynamical mechanisms inhibiting the appearance of chaos in such a case. As the quantum dynamics of a system is defined as a function of its classical dynamics – e.g. quantum chaos is defined as the quantum regime of a system whose classical dynamics is chaotic – we focus here on the dynamical regimes of classical atoms inside a well. We show that when chaos is inhibited, the motions in the two directions of space are frequency locked in most of the phase space, for most of the parameters of the lattice and atoms. This synchronization, not as strict as that of a dissipative system, is nevertheless a mechanism powerful enough to explain that chaos cannot appear in such conditions.

The dual frequency anisotropic Magneto-Optical Trap

Abstract 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.

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

Cold atoms are a tremendous tool to study the transition between the classical and the quantum world. Numerous approaches have been followed, as e.g. the realization of quantum logical gates [1,2], or the study of the properties of a Bose-Einstein condensate. The dynamics of classical cold atoms have also been investigated, mainly through instabilities of the disordered cloud produced by a magneto-optical trap [3–6]. However, the richer dynamics is expected in ordered potential, as those obtained with optical lattices. In such potentials, atoms, in their travel from site to site, can exhibit a very complex dynamics, including chaos. Up to now, the experimental works in this domain are very limited. Quantum chaos has been studied for atoms in the wells of a 1D kicked potential [7,8], and some works described the diffusion of atoms in optical lattices [9].

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

Cold atoms are a tremendous tool to study the transition between the classical and the quantum world. Numerous approaches have been followed, as e.g. the realization of quantum logical gates [1,2], or the study of the properties of a Bose-Einstein condensate. The dynamics of classical cold atoms have also been investigated, mainly through instabilities of the disordered cloud produced by a magneto-optical trap [3–6]. However, the richer dynamics is expected in ordered potential, as those obtained with optical lattices. In such potentials, atoms, in their travel from site to site, can exhibit a very complex dynamics, including chaos. Up to now, the experimental works in this domain are very limited. Quantum chaos has been studied for atoms in the wells of a 1D kicked potential [7,8], and some works described the diffusion of atoms in optical lattices [9].