The exact solution (Green’s function) of a parabolic equation describing the motion of neutral atoms in the field of a hollow TEM 01 * mode of laser radiation is found. The positions of the focus and the width of the focal spot are found on the basis of this solution for various configurations of the laser atomic beam.
The motion of paraxial atomic beams in a laser radiation field is studied within the framework of a parabolic equation. Exact analytical solutions of the parabolic equation are found for a variety of potentials featuring a nonuniformity in the propagation direction. Special attention is paid to the propagation of cold atomic beams in the gradient field of the TEM01* laser radiation mode. Explicit analytical expressions are found for the position of the focal points, focal spot radius, and spatial intensity distribution.
The focusing of an atomic beam using near-resonant laser light is considered. Path-integral techniques are employed to transform the problem into a standard diffraction integral. This approach is general and allows us to deal with thick laser lenses. Starting from the basic form of the potential energy for an atom in a laser beam, we derive the propagation kernel for the atomic wave function for the particular case of a TEM01*, or doughnut, mode laser beam. Both the full three-dimensional propagation kernel and its paraxial approximation are discussed. We show that the paraxial case can be obtained from the three-dimensional case by a stationary-phase approximation of the propagation equation. Numerical results for the focusing of a Gaussian atomic beam are presented. These results show that spot diameters on the order of 20 Å are obtainable for many reasonable choices of laser and atomic beam parameters and that for most of these cases the thin-lens approximation is not valid. The effects of the lowest-order aberrations are also briefly discussed. Spherical aberration is found to contribute significantly to the focal spot diameter, at least for the doughnut mode laser beam considered here.
We propose a new method to generate a focused hollow laser beam by using an azimuthally distributed 2π-phase plate and a convergent thin lens,and calculate the intensity distribution of the focused hollow beam in free propagation space.The relationship between the waist w0 of the incident collimated Gaussian beam and the dark spot size of the focused hollow beam at the focal point,and the relationship between the focal lenght f of the thin lens and the dark spot size are studied respectively.The optical potential of the blue-detuned focused hollow beam for^85 Rb atoms is calculated.Our study shows that when the larger waist w of the incident Gaussian beam and the shorter focal length f of the lens are chosen,we can obtain an extremely small dark spot size of the focused hollow beam,which can be used to form an atomic lens with a resolution of sereval angstroms.
We propose a new method to generate a focused hollow laser beam by using an azimuthally distributed 2π-phase plate and a convergent thin lens, and calculate the intensity distribution of the focused hollow beam in free propagation space. The relationship between the waist w o of the incident collimated Gaussian beam and the dark spot size of the focused hollow beam at the focal point, and the relationship between the focal length f of the thin lens and the dark spot size are studied respectively. The optical potential of the blue-detuned focused hollow beam for 85 Rb atoms is calculated. Our study shows that when the larger waist w of the incident Gaussian beam and the shorter focal length f of the lens are chosen, we can obtain an extremely small dark spot size of the focused hollow beam, which can be used to form an atomic lens with a resolution of several angstroms.
The focusing of a neutral atomic beam using near-resonant laser light is considered. The results of a path integral solution to the Schrodinger in the stationary phase approximation are presented. The details of the derivation of the propagation kernel are presented elsewhere [1]. This approach is general and allows us to deal with "thick" laser lenses. Numerical results for the focusing of a Gaussian atomic beam are presented. These results show that spot diameters on the order of 20 Angstroms are obtainable for many reasonable choices of laser and atomic beam parameters, and that for most of these cases the thin lens approximation is not valid.
Recently, the focusing of an atomic beam using a laser has been considered by Balykin and Letokhov.1 Their calculations explicitly assume the thin lens approximation. Here, using path integral techniques, we derive the focal length and lowest-order aberrations of the laser atomic beam lens as a function of both laser and atomic beam parameters without making the thin lens approximation. Starting from the basic form of the potential energy for an atom in a laser beam, the propagation kernel is derived for the TEM(01)* or donut mode beam. From this result the focal length and lowest-order aberrations can be found for any atomic beam profile. We consider in particular a Gaussian atomic beam. Both the full 3-D propagation kernel and its paraxial approximation are discussed. We show how the paraxial case can be obtained from the 3-D case via a stationary phase approximation of the propagation equation.