Focusing a slow atom beam using a complex light field

V. I. Balykin, Vladilen S Letokhov, В. В. Климов

Hans Pauly

H. Merimeche, Ralph Peter Bertram, D. Haubrich +4 more

Summary form only given. Laser cooling methods provide the possibility to obtain very well collimated and slow atomic beams. These intense sources have attracted new interest in the manipulation of atomic trajectories. Atom optical schemes based on the optical dipole force are very attractive, for example in atom lithography where atomic beams are focused by standing wave light fields, to create periodic nanostructures.

Dmitry Strekalov, Andrey B. Matsko, Anatoliy A. Savchenkov

Specially designed focusing of light beams has been proposed as a means of improving the performances of optical buffers based on cells containing hot atomic vapors (e.g., rubidium vapor). There is also a companion proposal improve performance by use of incoherent optical pumping under suitable conditions. Regarding the proposal use focusing: The utility of atomic-vapor optical buffers as optical storage and processing devices has been severely limited by nonuniform spatial distributions of intensity in optical beams, arising from absorption of the beams as they propagate in atomic-vapor cells. Such nonuniformity makes it impossible the physical conditions throughout a cell, thereby making it impossible the performance of the cell as an optical buffer. In practical terms simplified for the sake of brevity, to optimize as used here means design the cell so as maximize the group delay of an optical pulse while keeping the absorption and distortion of the pulse reasonably small. Regarding the proposal use incoherent optical pumping: For reasons too complex describe here, residual absorption of light is one of the main impediments achievement of desirably long group delays in hot atomic vapors. The present proposal is directed toward suppressing residual absorption of light. The idea of improving the performance of slow-light optical buffers by use of incoherent pumping overlaps somewhat with the basic idea of Raman-based slow-light systems. However, prior studies of those systems did not quantitatively answer the question of whether the performance of an atomic vapor or other medium that exhibits electromagnetically induced transparency (EIT) with Raman gain is superior that of a medium that exhibits EIT without Raman gain.

U. Janicke, Martin Wilkens

H. Merimeche

Laser cooling methods provide the possibility to obtain very well collimated and slow atomic beams. These intense sources have attracted new interest in the manipulation of atomic trajectories. Atom optical schemes based on the optical dipole force are very attractive, for example in atom lithography where atomic beams are focused by standing wave light elds, to create periodic nanostructures. However, in applications where more complex structures are desirable or decoherence due to spontaneous emission has to be avoided, magnetic atom optical components are more attractive. For example, at and curved atomic mirrors with high reflectivity and low surface rough ness can be built from periodically magnetized videotapes. First, with a collimated and polarized cesium atomic beam from a Zeeman-slower apparatus, we have investigated the deflection of the atomic beam by a sinusoidally magnetized videotape with a period length of 30 μm. From these measurements we have determined the magnetic eld strength at the surface to be 0.05 Tesla. The reflectivity has been found to be consistent with 100%. The very large eld gradients produced by the tape can be exploited to guide atoms on curved trajectories with small radii of curvature. With a radius of 9.5 cm we have obtained a maximum deflection angle of 25° which is limited by technical constraint. Second, we have built a setup based on a 2D-MOT for generating a slow atomic beam with a velocity of 20 m/s. After leaving the optical collimation and the optical polarization stages, the atomic beam is reflected after one bounce onto the videotape up to angles as large as 7°. We exploited the natural curvature of our videotape and we demonstrated the focusing of the atomic beam after one and two bounces depending on the curvature of the videotape. The focal length and the angles of deflection enable to deduce the local radii of curvature. We have confronted our results by testing the focusing of the videotape with a red laser and by performing a numerical simulation which prove the consistency with the atomic beam experiments.