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

used to cool 87 Rb experimentally, emphasizing those features common to all
iterations of the experiment. This section represents an updated version of
our original paper proposing a single-photon cooling scheme appropriate for
87 Rb [94]. In all iterations of the experimental process a sample of magneti-
cally trapped 87 Rb was transfered into a conservative optical dipole trap via
the single-photon cooling process. The shape and construction of the optical
dipole trap varied with each iteration. For the sake of simplicity, I will use a
generic optical potential in this overview of the single-photon cooling process
and describe the details of each iteration in later sections.
To obtain the magnetically trapped sample of 87 Rb, several steps are
taken. Atoms are initially loaded into the upper MOT from room temperature
87 Rb vapor. A discussion of the design of the upper chamber and source of
Rb can be found in Sec. 3.1.1. As the upper MOT is loaded, the push beam
transfers 87 Rb atoms into the lower chamber where they are recaptured in the
lower MOT. When optimized, we are able to collect atoms in the lower MOT at
a rate of roughly 10 8 atoms/sec. This rate drops off after a few seconds due to
saturation effects. When loading the lower MOT we run approximately 1.6 A
of current through the lower magnetic quadrupole coils thereby producing a
magnetic field gradient of B ′ = 8 G/cm (see Sec. 2.4 and Sec. 3.3 for more
details). The lower MOT beams are typically detuned −15 MHz from the
|F = 2〉 → |F ′ = 3〉 cycling transition, have a waist of ∼ 1 cm and an optical
power of 7 mW each.
We typically operated the lower MOT loading stage for approximately
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