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

error signal
λ λ λ
to saturation
absorption
spectrometer
Figure 4.11: Distribution fo the repump laser. Figure courtesy of Gabriel Price.
a glass plate. The pump beam counter-propagates the probe beams but overlaps with
only one of them. The difference between the two probe beams is detected using a
differential photodetector to remove the Doppler-broadened background signal.
Figure 4.12: Repump laser saturated absorption spectroscopy setup. Figure courtesy of
Gabriel Price.
The frequency of the laser is modulated directly by dithering the piezo stack on
the diode laser cavity at 20 kHz. The disadvantage of this design is the introduction of
a small amount of frequency noise on the laser. However, during normal operation of
the experiment this effect is negligible.
Figure 4.13 shows the error signal for the repump laser. The laser is again locked
to the most prominent line, in this case this is the |F = 1〉 → |F ′ = 1/2〉 crossover
transition. This locks the laser 78.5 MHz to the red of the |F = 1〉 → |F ′ = 2〉
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λ
to