Experiments to Control Atom Number and Phase-Space Density in ...

shifts. First a frequency shift of 103 MHz is caused by the AOM used to pick-off the
spectroscopy beam. In addition the laser is locked to the |F = 2〉 → |F ′ = 2/3〉
transition, which is detuned by 133 MHz from the |F = 2〉 → |F ′ = 3〉 transition. The
pump beam is shifted by 88 MHz relative to the frequency of the probe beam by double-
passing the 44 MHz AOM. This implies that the pump and the probe beam interact with
atoms having a velocity such that their Dopplershift corresponds to 44 MHz. Therefore
the overall error signal is shifted by 44 MHz relative to the error-signal that would result
if the beam interacted with atoms with zero velocity.
Most of the light passes through the 103 MHz AOM and is deflected at a polarizing
beamsplitter cube. The beam then double passes an 80 MHz AOM with a 40 MHz
bandwidth. The first-order diffraction beam double-passes a quarter waveplate and thus
passes straight through the polarizing beam splitter cube on the second incidence. This
beam is then distributed to the three slave lasers, where it serves as the seed required for
injection locking (see section 4.3.1.3). Because of the AOM double pass, the injection
beam, and thus the frequency of the slave lasers, can be tuned between 80 and 160 MHz
to the red of the |F = 2〉 → |F ′ = 3〉 transition. 80 MHz AOMs, used as shutters for
the beam, shift the frequency of the slave lasers, so that the final detunings are between
0 and 80 MHz to the red of the |F = 2〉 → |F ′ = 3〉 transition. The zeroth order beam
from the 80 MHz AOM is coupled into a Fabry-Perot cavity. This way it is easy to
ensure single-mode operation of the MOT master laser.
4.3.1.2 Repump Laser
The design of the repump laser is identical to the design of the MOT master laser.
The power required in the repump laser is significantly lower than the power required in
the MOT laser and it is therefore not necessary to further increase the laser power.The
distribution of the output power is shown in figure 4.11.
After the optical isolator a small amount of power is split off using a polarizing
beam splitter cube. This beam is used in the repump spectroscopy lock, which varies
slightly from the MOT master spectroscopy setup, see figure 4.12. The spectroscopy
beam is split into a strong pump beam and two co-propagating weak probe beams using
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