The focusing and collimation effects of cold atomic clouds passing through a far red-detuned focused Gaussian beam

Abstract

This work has theoretically studied the optical properties, such as the object-image relation and the focal length of the atom-optical lens created by far red-detuned Gaussian laser beam perpendicular to the propagation direction of the atomic cloud. Furthermore we have thoroughly studied the collimation effect when the cold atomic clouds passing through the laser beam. The effective transverse temperature can reach tens nanokelvin, which is far smaller than that by 1D polarization gradient cooling. . IntroductionAtom-optical lens is one of the fundamental atom-optical element, which can focus, collimate, image and transmit the atom beam. Therefore it has been implemented in many ways, such as, atom lithography, atom interferometry and atom interference. Up to now two kinds of atomic lens, based on magnetic or far-detuned optical fields, have been developed. A focused Gaussian laser beam with red detuning is also can be used as an atom-optical lens. Early experiments demonstrated this kind of atomic beams focusing using the dipole force [1]. The focusing dynamics of a trapped BEC interacting with laser pulses have also been investigated [2]. In previous work we have experimentally studied the ultracold atomic cloud and BEC wave packet passing through focused red-detuned Gaussian laser beam [3]. In this work the object-image relation and the aberration of the atomic lens created by the red-detuned Gaussian beams are studied in detail.The one-dimensional collimation effect of wave packet is interesting because it is very useful in many important aspects required low divergence sources. One method of producing such highly collimated beams is using one-dimensional cooling technology. Another one-dimensional collimation method is also realized when atomic beam through atomic lens based on magnetic field [4]. We also investigate the collimation of wave packet and discuss how to control the collimation by adjust the related parameters. Our method has the advantage of small scale and flexable adjustment of the parameters of the atomic lens. This work is helpful to further understand the properties of atom-optical lens and one-dimensional collimation effect.