Coherence properties of a continuous atom laser

• Published in: Journal of modern optics Vol. 47; no. 14-15; pp. 2671 - 2695
• Main Authors: Castin, Y., Dum, R., Mandonnet, E., Minguzzi, A., Carusotto, I.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: London Taylor & Francis Group 01.11.2000; Taylor & Francis
• Subjects: Classical and quantum physics: mechanics and fields; Condensed Matter; Exact sciences and technology; Fundamental areas of phenomenology (including applications); Lasers; Matter waves; Optics; Phase coherent atomic ensembles ; quantum condensation phenomena; Physics; Statistical Mechanics; Coherence length; Atom lasers; Atomic beams; Theoretical study; Evaporative cooling; Atomic coherence; Bose-Einstein condensation
• ISSN: 0950-0340; 1362-3044
• DOI: 10.1080/09500340008232189

We investigate the coherence properties of an atomic beam evaporatively cooled in a magnetic guide, assuming thermal equilibrium in the quantum degenerate regime. The gas experiences two-dimensional, transverse Bose-Einstein condensation rather than a full three-dimensional condensation because of the very elongated geometry of the magnetic guide. First order and second order correlation functions of the atomic field are used to characterize the coherence properties of the gas along the axis of the guide. The coherence length of the gas is found to be much larger than the thermal de Broglie wavelength in the strongly quantum degenerate regime. Large intensity fluctuations present in the ideal Bose gas model are found to be strongly reduced by repulsive atomic interactions; this conclusion is obtained with a one-dimensional classical field approximation valid when the temperature of the gas is much higher than its chemical potential, k B T » |μ|.