2D laser collimation of a cold Cs beam induced by a transverse <i>B</i> field

We describe transverse collimation of a continuous cold cesium beam (longitudinal temperature 75 μK) induced by a two-dimensional, blue-detuned near-resonant optical lattice. The mechanism described for a lin-

-lin configuration is made possible by the application of a transverse magnetic field <i>B</i>_. The phenomenon described differs from gray molasses, for which any small magnetic field degrades cooling, as well as from magnetically induced laser cooling in red-detuned optical molasses, where there are no dark states. The lowest transverse temperature is experimentally found to vary as <i>B</i>²_ . The collimated flux density shows a dip as a function of <i>B</i>_, the width of which is proportional to the cube root of the laser intensity, general features predicted by our semiclassical model. This technique provides a sensitive tool for canceling transverse magnetic fields <i>in situ</i> at the milligauss level.