We consider the velocity-dependent light pressure force on a two-level atom interacting with a two-dimensional nearly resonant standing-wave light field. We show that there can be anisotropic cooling–heating forces that will cool the atoms along one field axis while heating them along the perpendicular axis. The force is identified as a spontaneous vortex force associated with the local traveling-wave character of the two-dimensional field. We provide a simple interpretation of this anomalous force in terms of the interplay between the vortical momentum flow of the light field and a motion-induced population transfer between the ground and excited atomic states.
© 1994 Optical Society of America
Original Manuscript: February 23, 1994
Published: November 1, 1994
T. Cai and N. P. Bigelow, "Anisotropic velocity-dependent vortex forces: two-level atoms in two-dimensional standing waves," Opt. Lett. 19, 1768-1770 (1994)