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

ent results in a magnetic field gradient of B ′ = 48 G/cm. Mode mismatch
between the optically pumped atomic sample and the magnetic trap results
in heating. The final temperature of the magnetically trapped sample was
typically in range of 50-100µK. Under these conditions, the 1/e 2 radius of
the magnetically trapped atomic cloud was ∼ 500µm. These atoms serve as
the initial condition for further cooling via the single-photon cooling process
during which time they are transfered into an optical trap.
Then next step in the single-photon cooling process involves position-
ing a conservative optical dipole trapped in the wings of the magnetically trap
sample. As stated in the introduction to this chapter, the details of the opti-
cal dipole trap evolved as the experiment progressed. To keep this overview
simple, I will introduce an optical trap representative of the actual potentials
used which encompasses their key features. The details of each iteration of
the optical trap used during the experiments are discussed in the next several
sections. For now, consider a blue detuned optical sheet placed below the mag-
netically trapped atomic sample. Because the sheet is tuned below the atomic
resonance frequency, it produces a repulsive barrier. This barrier is capable of
levitating the atoms with sufficiently high optical intensity. Figure 4.1(a) il-
lustrates the geometry under consideration. Figure 4.1(b) shows the potential
landscape for atoms in the |F = 2,mF = 2〉 state due to the magnetic field
gradient, gravity, and the optical sheet. For comparision, Fig. 4.1(c) shows
the potential landscape for atoms in the |F = 1,mF = 0〉 state due to gravity
and the optical sheet. Notice that atoms in this state are decoupled, to first
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