Abstract

The interaction between two laser fields and a three level atom in a Λ configuration has been of considerable interest for many years. The force due to two traveling waves has already cooled atoms below the single photon recoil limit,^[1] even though there is no net average semi-classical force on the atom. More recent theory has solved the steady state optical Bloch equations and shown that <F₀>, the net average semi-classical force on a stationary three level atom in two standing waves, is unbounded and has components with characteristic spatial variations on scales BOTH much longer and much shorter than an optical wavelength.^[2] The components which are much longer than the optical wavelength depend on the phase difference, φ, between the two standing wave fields. In particular, <F₀> should be zero when φ = nπ/2, where n is an integer, and should be anti-symmetric with respect to these force zeroes. For certain field conditions, the force is simply proportional to sin(2φ). An intuitive understanding of this force has been provided by modeling the system not in terms of the original two ground states and the excited state, but in terms of linear combinations of the ground states, which have been referred to as dressed states.^[3]

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