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

excited state through the relation
1
τ = ω3 0
3πǫ0c3 2J + 1
2J ′ + 1 |〈J||µ||J ′ 〉| 2
to have the value 3.584 24(74) × 10 −29 C · m.
2.7 Laser Frequency Control
(2.95)
The laser beams used during the experiment can be roughly divided
into two categories: those far from resonance with any transition in 87 Rb and
those close to an atomic transition, specifically the D2 transition. The absolute
frequency of the laser beams which are far from resonance is not crucial (their
role in optical dipole trapping is discussed elsewhere). There is a need however,
to control the frequency of the near resonance laser beams. These beams are
used for laser cooling and to induce a state change in 87 Rb atoms during the
single-photon cooling process. This works only if the frequency of these beams
are tuned correctly. Typically the frequency of these beams must be brought to
within a few natural linewidths of the D2 transition frequency. The frequency
of this transition is ≈ 384 THz while its natural linewidth is only ≈ 6 MHz.
Therefore the frequency of these laser beams must be controlled to the ∼ 1
MHz level, or to 1 part in 10 8 . A laser frequency locking scheme based around
saturation absorption spectroscopy is use for this purpose.
2.7.1 Doppler Broadening
At room temperature, Doppler broadening is usually the dominant con-
tribution to the observed width of lines in atomic spectra. For example, the
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