M5L24h.txt

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So what you're going to discuss now
are the theme is Fano profiles.
And they want to discuss two-photon absorption features.

So we have discussed the case where
the one-photon detuning, we want to go now
to a large one-photon detuning delta 2.
And the new feature now is that this really
separate the window of electromagnetic
induced transparency from the port absorption features.

So let me just draw a diagram of the states.
As usual, we have our two states in the lambda transitions, g
and f.
We have this continuum of the excited state.
But now-- and this is what often is
done in the experiment-- you're not
using raman lasers, which are in resonance with the excited
state.
You're using raman lasers.
Here is the strong coupling lasers, which are far detuned.
So here we have detuning, which for laser 2 called gamma 2.
The raman frequency's omega 2.
Here we have-- this is the weak pole [? laser ?] omega 1.
And the detuning value, let's call it gamma 1.
So in order to keep the situation simple,
we use a weak pole [? laser. ?] Omega 1 is small.
And our raman detuning delta is the difference
between the two similar photons detuning, capital delta 2 tool
minus capital delta 1.
For these situations, there are nice analytic expressions.
And together with the class notes,
I will post a wonderfully clear paper
by Lounis and Cohen-Tannoudji, where the two authors discuss
this situation.

But let's just sort of figure out what are
the features in this system.
Let's just kind of go through different situations.
One is if the raman detuning is 0,
we should always get the phenomenon
of electromagnetically-induced transparency.
If you don't have any coupling, then we simply
have a two-level system.
And if we tune omega 1 into resonance,
we get simple single photon absorption.

So if we look at the system of the three levels
and we are asking what are now the relevant processes,
one limit is of course the trivial limit
that we have single photon absorption.