Single-Photon Atomic Cooling - Raizen Lab - The University of ...

Figure 4.25: Number (■) and temperature (●) of cooled atoms as a function
of hp (height of the depopulation beam above the trough vertex). The positive
slope of T (z)
O reflects energy gained by atoms in free fall. For hp > 100µm,
the additional energy increases the loss rate from the optical trough. For
hp < 100µm spatial overlap of the pump beam and optical trough beams
reduces the excitation probability and hence the capture rate. The highest
phase-space density is achieved at hp = 41µm.
overlap the depopulation beam. This partial occlusion of the depopulation
beam decreases the chance an atom will undergo the depopulating transition,
resulting in a decreased transfer rate.
As discussed in Sec. 1.4 the recoil temperature Tr = 362 nK is the
fundamental limit to the single-photon cooling process. However, as indicated
in Fig. 4.25, the final temperatures achieved during the single-photon cooling
process are well above this limit even for the small values of hp. If we where
cooling a 1-D ensemble then this residual energy could only be attributed
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