Magneto-optical trap near a surface

Recoil and momentum diffusion of an atom close to a vacuum-dielectric interface

“…We then made explicit predictions for simple atoms (J g = 0, 1/2) in the vicinity of a flat dielectric surface. These results allow for precise estimates of the effects of spontaneous emission when atoms are either reflected from an evanescent wave mirror [15,16,18] or trapped in a two-dimensional waveguide-like field configuration in the vicinity of a surface [19][20][21][22][23][24][25].…”

“…Our results are also relevant for radiative atom traps in the vicinity of material surfaces [19][20][21][22][23][24][25], where momentum diffusion due to spontaneous emission may be one of the limiting factors for the temperature.…”

“…This may have been expected from the enhanced fluorescence rates Γ ,⊥ (z) compared to Γ ∞ , as well as from the spatial subwavelength structure of both the evanescent field and the vacuum field correlations. Finally, we note that this diffusion tensor also translates into an increased temperature limit for radiative atom traps in the vicinity of surfaces [19][20][21][22][23][24][25].…”

“…Being based upon the interaction between an atom and an evanescent laser wave propagating along the surface of a dielectric prism, it already allowed for detailed experimental investigations of fluorescence rates [13,14], single optical pumping cycles [15,16] and ground-state energy shifts [17] at distances of order λ = c/ω A from the interface (ω A is the atomic transition frequency). Spontaneous emission in the evanescent wave is also used in reflection cooling techniques [15,16,18] that have been proposed for radiative atom traps in the vicinity of surfaces [19][20][21][22][23][24][25]. From these experiments it has become apparent that a proper description of the fluorescence rates and the energy levels has to take into account the distortion of the electromagnetic field due to the presence of the dielectric.…”

“…(22). To solve this equation approximately, we observe that the last term on the rhs is small compared to the term involving Γ ∞ on the lhs, because of the low saturation limit s 0 ≪ 1 [condition (50)].…”