Broadband stimulated cooling

Abstract

A new method is proposed1 for laser-cooling atoms with Doppler shifts an order of magnitude larger than the homogeneous line width of the atomic transition. This allows one to stop a substantial fraction of an atomic beam without chirping the laser or Zeeman tuning the atoms. Stimulated cooling has been shown in previous work2 to lead to velocity damping rates that can be several orders of magnitude greater than spontaneous force cooling. In the present method, this large damping rate is exchanged for a broad bandwidth by crossing two traveling waves at an oblique angle 2θ so that a dipole-force potential well is created with a wavelength λ/ sin θ which is much greater than that of either traveling wave. See Fig. 1. The resulting stimulated cooling forces may be called broadband since the region of linear velocity damping is increased by a factor 1/sin θ which may be a factor of 10 or more. In so- dium, the capture velocity can be as high as ±120 m/s, which permits stopping 0.1% of the flux of a 500 K atomic sodium beam in a distance of 300 μm and a time of a few micro seconds, This is more than 100 times faster than current methods. © 1992 Optical Society of America