Long-distance channeling of cold atoms exiting a 2D magneto-optical trap by a Laguerre-Gaussian laser beam.

Using a blue-detuned laser, shaped into a nearly Laguerre-Gaussian (LG) donut mode, we channel atoms exiting a two-dimensional magneto-optical trap (2D-MOT) over a 30 cm distance. Compared to a freely propagating beam, the atomic flux (∼10(10) at/s) is conserved whereas the divergence is reduced from 40 to 3 mrad. So, 30 cm far the 2D-MOT exit, the atomic beam has a 1 mm diameter and the atomic density is increased by a factor of ∼200.

First measurements of the index of refraction of gases for lithium atomic waves.

We report the first measurements of the index of refraction of gases for lithium waves. Using an atom interferometer, we have measured the real and imaginary parts of the index of refraction n for argon, krypton, and xenon as a function of the gas density for several velocities of the lithium beam. The linear dependence of (n-1) with the gas density is well verified.

Parallel temperatures in supersonic beams: ultracooling of light atoms seeded in a heavier carrier gas.

Supersonic expansion is a very powerful tool to produce an atomic beam with a well defined velocity and, by seeding a test gas in such an expansion, the energy of the test gas can be transferred, at least partially, to the very-low-temperature carrier gas. The case usually studied is the one of a heavy gas seeded in a light carrier gas and, in this case, the parallel temperature of the seeded gas is always larger than the one of the carrier gas. In the present paper, we study the opposite case which has received less attention: when a light gas is seeded in a heavier carrier gas, the parallel temperature can be substantially lower for the seeded gas than for the carrier gas.

Experimental demonstration of phase control of dispersion effects for an ultrashort pulse train propagating in a resonant medium.

We present an experiment in which an ultrashort pulse train propagates resonantly through anoptically dense vapor of atomic rubidium. The sequence obtained from a Fabry-Perot interferometer comprises nearly 10 regularly time-delayed and mode-locked pulses. We show that a sequence with phase shift phi = 0[2pi] between two successive pulses propagates with important temporal distortion, whereas a sequence with phi = pi[2pi] experiences few propagation effects, thus leading for the first time to our knowledge to the possibility of phase control of dispersion effects for an ultrashort pulse train.