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

Chapter 5
Stimulated Raman transitions
A Raman transition is a two-photon process that couples two different energy levels
and transfers population from one state into the other. This is done by absorbing one
photon from a monochromatic light source (usually a laser) and reemitting a photon
with a different frequency. Stimulated Raman transition means that the emission is
also driven by an external monochromatic field (second laser beam). For an efficient
population transfer, the beams should be detuned by the frequency corresponding to
the energy difference of the two coupled states.
In section 5.1 we will give a brief overview of stimulated Raman transitions,
before we present the fundamental limits in section 5.2. The following sections will
present a theoretical description of stimulated Raman processes, first for a simple
three-level system in section 5.3, then generalizing to multi-level systems in section 5.4.
Lastly, we will describe the effects due to an external magnetic field.
5.1 General description of spatially resolved stimulated Ra-
man transitions
The ground state 2 S1/2 in Sodium splits into two hyperfine levels with F=1 and F=2.
The difference frequency between those two states is 1.772GHz. The laser we use to
cool and trap the atoms in a MOT, is tuned to the |3 2 S1/2, F = 2〉 → |3 2 P3/2, F = 3〉
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