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

labeled 1, 2 and 3 in the Fig. 3.21. Beam paths 1 and 2 are used to form
the “V”-shaped portion of the optical trough. Each of these beams passes
through a telescope formed with a 60 mm and 200 mm lens. The beams are
spatially filtered at the focus of the 60 mm lenses. The nominal spacing of
the telescope was 260 mm but the 200 mm lenses were placed on translation
stages, giving control of the beam curvature after the telescope. We used this
degree of freedom to adjust the location of the focus of each beam in the
optical trough. After passing though the telescope, each beam passes through
a cylindrical lens. These two cylindrical lenses were oriented at a right angle
to each other so that when the two beams were combined with a polarizing
beam splitter they would form the correct “V” shape. After being combined,
the two beams were focused into the chamber with a 63.5 mm lens along the ˆx
direction. The astigmatism introduced into each beam by the cylindrical lens
caused the beams to have 1/e 2 waists of 10µm × 100µm at the location of
the optical trough.
The optical end caps were derived from beam path 3. To produce
two end caps we pass this beam through an AOM driven at two frequencies
which were nominally 84 MHz and 123 MHz. After passing though the AOM
unneeded orders were blocked. The unblocked orders passed through a cylin-
drical lens and were focused into the lower chamber by a 50 mm lens. The end
caps travel along the ˆy direction and intersect the two beams which form the
“V”-shape. The spacing of the end caps was typically 110µm, but by changing
the frequencies driving the AOM this could be adjusted. The measured and
121