Copyright by Kirsten Viering 2006 - Raizen Lab - The University of ...

Figure 6.2: Dependance of the final state probability of pulse duration τ.
In a future experimental setup, the detuning between the two Raman beams will
be created by an Acousto-Optic Frequency Shifter (Brimrose TEF-1700-350-589) with
an optical threshold of 100W/mm 2 and a diffraction efficiency of 14.8% at a wavelength
of 532nm. The time development of the final state probability depends critically on the
intensities of the two Raman beams. So it is important to note that the following calcu-
lations are based on beams with 7.6 mW with a beam waist of 50µm. The large beam
waist guarantees that the intensity in the Raman resonance region is approximately
constant. A plot of the time dependance is shown in fig. 6.2. After a pulse duration of
337.3µs the population transfer reaches 98.8%.
With a pulse of length 337.3µs, less than 20kHz detuning from the Raman
resonance frequency will reduce the population transfer significantly, as can be seen in
fig. 6.3. This results in a spectral resolution of less than 250nm if we take the magnetic
field gradient to be 150G/cm. Nevertheless, the spatial resolution is severely limited
due to the initial velocity of the atoms and their acceleration during the Raman pulse.
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