Precise control of launch velocity vector for cold atomic cloud based on moving optical molasses

Abstract

We propose a method for precise control of the launch velocity vector of a cold atomic cloud. By independently adjusting the relative detuning of three pairs of orthogonal counter-propagating laser beams in moving optical molasses, this method achieves accurate regulation of three-dimensional velocity components, thereby realizing precise calibration of atomic launch direction. It can significantly reduce the complexity of mechanical adjustments and mitigate residual errors caused by mechanical tuning, with the advantages of simplicity and easy implementation. Experimental verification on an 87Rb atomic fountain clock shows that the spatial distribution of the cold atomic cloud is obtained via horizontal velocity scanning, and the tilt deviation of the fountain clock is evaluated and corrected. Ultimately, the angles between the cold atom launch direction, the central axis of the fountain clock, and the vertical direction are all less than 0.1 mrad. Time-of-flight signal analysis indicates that under 3% laser power fluctuation, the long-term instability (5000 s) of the velocity reaches 62 μm/s. This method holds significant application value for atomic fountains, atomic gravimeters, atomic gyroscopes, and other cold atomic precision instruments based on moving molasses.