An optically-guided atomic fountain

We have performed the experiment of optically guided atomic fountain by using a cylindrical hollow laser beam (HLB). Cold atoms after polarization-gradient cooling (PGC) are launched upward in a rather simple way by just varying rapidly the current of vertical directional Helmholz coils, so that the frequency difference between the upgoing and the downgoing cooling laser can be obtained due to the atomic Zeeman shift. The entire process is equivalent to the moving molasses scheme, and consequently atoms are cooled down below the Doppler limit. We observe that 0.5% of the launched atoms are detected without the HLB, whereas tenfold enhancement of the HLB-guided atomic fountain is clearly obtained without appreciable broadening of the time of flight (TOF) signal. We have demonstrated tenfold enhancement of the atomic funneling efficiency for the HLB-guided atomic fountain which may lead to the improved performance of atom optical experiments based on atomic fountain such as Rb atomic clock. Moreover, if two ground-state hyperfine levels experience the similar light shifts at the appropriate detuning, it may be also useful to apply to Rb atomic fountain clock