Tight focusing of an atomic beam by the near field of diffracted laser light
Balykin V. I., Letokhov V. S., Klimov V. V.
It is shown on the basis of classical dynamics that the near field of laser light, which arises upon the diffraction of a plane light wave by an aperture small in comparison with the wavelength, gives rise, by virtue of a gradient force, to a tight focusing of a normally incident atomic beam if the detuning of the frequency of the laser light from resonance is negative. Explicit expressions are derived for the trajectories of particles and for the caustic surface in the approximation of a weak scattering potential. The defocusing which would result from a velocity spread of the beam atoms is estimated.