The technique of laser cooling, whose basic idea was proposed in 1975 [1[1] W.D. Phillips, Rev. Mod. Phys. 70, 721 (1998).], provided the development of many important areas like high-resolution spectroscopy [2[2] W.M. Itano, J.C. Bergquist, R.G. Hulet and D.J. Wineland, Phys. Rev. A 36, 2220 (1987).], atomic clocks [3[3] N.F. Ramsey, Metrologia 42, S1 (2005).] and quantum gases confined in magnetic or optical traps [4[4] S. Chu, Scientific American 266, 71 (1992)., 5[5] E.A. Cornell and C.E. Wieman, Rev. Mod. Phys. 74, 875 (2002).]. Among the techniques applied to cooling neutral atoms is the optical molasses [6[6] P.D. Lett, W.D. Phillips, S.L. Rolston, C.E. Tanner, R.N. Watts and C.I. Westbrook, J. Opt. Soc. Am. B 6, 2084 (1989).] that will be explored in this work. Here we study the standard molasses and a new alternated molasses configuration, which consists of turning on just one pair of counter-propagating laser beams per cycle, and alternating this pair between the three spatial directions. We analyse the two techniques under the lens of the radiation force, by exploring a semiclassical treatment, in order to obtain the minimum energy attained by each of them at the end of the cooling process. We compare, then, these two cooling techniques, pointing out their advantages.
Keywords:
Laser cooling; Optical molasses; Semiclassical treatment; Doppler limit
