Abstract
To laser cool atoms in an atomic beam, it is necessary to repeatedly excite the atoms with a counterpropagating laser beam. One method of doing this uses a "chirped" laser frequency to compensate for the changing Doppler shift of the slowing atoms. Although most implementations of chirp cooling use only a single swept frequency,1,2 improved cooling efficiency can be obtained through multifrequency chirp cooling3,4 or broadband white-light cooling.5 We demonstrate a multifrequency chirp method using two simultaneously swept EM sideband orders that we used to bring a significant fraction of a thermal lithium beam to near-zero velocity. With this method, atoms with high initial velocities are slowed first by interaction with a second-order sideband and then additionally slowed by a first-order sideband. For a given frequency sweep range, this two-sideband technique requires an FM bandwidth that is only one-third that of single frequency chirp cooling. This improvement is especially important for cooling atoms, such as lithium, that have large initial Doppler shifts and therefore require a large frequency sweep range.
© 1992 Optical Society of America
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