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

4.2 Crossed Dipole Beam Configuration
This section reports on our first experimental implementation of single-
photon atomic cooling with a magnetically trapped sample of 87 Rb. While
the results presented in this section did not merit publication, they did offer
the first evidence that the single-photon cooling process worked. We felt en-
couraged that with improvements to the experimental apparatus and process,
single-photon atomic cooling could be made an efficient method. Because of
this, these results are presented with somewhat less rigor than in the next two
sections which represent published work. In this experiment, as in the later
iterations, we transfered atoms initially in the |F = 2,mF = 2〉 state from a
large volume magnetic trap into a smaller volume optical dipole trap via the
single-photon cooling process.
During this iteration of the experiment the optical dipole trap was
formed from two crossed laser beams at a wavelength of 1064 nm. Each beam
originated from a multi-mode ytterbium fiber laser with a maximum output
power of 10 W and a spectral bandwidth < 1 nm. This optical trap was placed
above magnetically trapped atoms as shown in Fig. 4.3. Because the laser
output frequency is well to the red of the D transition lines in Rb, it formed
an attractive potential whose depth can be found from Eq. 2.53 and knowledge
of the trap geometry. Figure 4.4 shows the calculated potential landscape for
atoms in the |F = 2,mF = 2〉 state due to the magnetic and optical traps
as well as gravity. In this figure, parameters consistent with experimental
values are assumed. The current in the magnetic coils is 15 A, resulting in
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