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

transition. However, the laser frequency is shifted by 80 MHz using an AOM after the
polarizing beam splitter cube, see figure 4.11. Thus the final laser frequency is detuned by
1.5 MHz from resonance, negligible compared to the 6 MHz linewidth of the transition.
The zeroth order signal from the 80 MHz AOM is coupled into a Fabry-Perot cavity, so
that single-mode operation of the repump laser can easily be verified.
Error Signal
a b c d e f
Repump Laser Frequency
Figure 4.13: Error signal of the repump laser. The marked transitions are due to the
following real and crossover transitions: (a) |F = 1〉 → |F ′ = 0〉, (b) |F = 1〉 → |F ′ =
0/1〉, (c) |F = 1〉 → |F ′ = 1〉, (d) |F = 1〉 → |F ′ = 0/2〉, (e) |F = 1〉 → |F ′ = 1/2〉, (f)
|F = 1〉 → |F ′ = 2〉
4.3.1.3 Slave Lasers
Three injection-locked slave lasers amplify the MOT master laser. The heart of
the slave laser is an inexpensive laser diode (Sharp GH0781JA2C) with a free-running
wavelength of 784 nm and 120 mW of power at 140 mA injection current. The diode and
a collimation lens are housed in a collimation tube (Thorlabs LT230P-B). The wavelength
of the laser diode can be tuned close to the resonant transition of rubidium by adjusting
the temperature. Good thermal control is achieved by mounting the collimation tube
inside a bronze block and regulating the temperature with a TEC. Stable current to
the slave lasers is provided by a PID based current controller. Figure 4.14 shows a
photograph of a slave laser with and without the aluminum housing surrounding the
diode laser setup.
58