Intense field population changes significantly, Stark shift induced by the laser field
profoundly modifies the energylevel structure leading to new resonances in the
optical susceptibility.
No relaxation!
From the Schrodinger Equation follows:
Lecture 24
Rabi Oscillations and Dressed Atomic States
(
(
( , )
( )
( ) exp
( )
( ) exp
a
a
a
b
b
b
r t
C
t u
r
i
t
C
t u
r
i
t
ψ
ϖ
ϖ
=
⋅

+
⋅

arrowrightnosp
arrowrightnosp
(
(
2
2
2
2
1
1
( )
cos
sin
C
t
t
t
∆
′
′
=
Ω
+
Ω
The same solution can be obtained from the Bloch equations.
The solution first obtained by Rabi
1
2
2
2
a
′
Ω
(
29
2
2
2
1
2
2
( )
sin
b
C
t
t
Ω
′
=
Ω
′
Ω
2
2
2
′
Ω
=
+ ∆
Ω
2
( )
( )
b
bb
C
t
t
ρ
=
2
2
( )
( )
1
a
b
C
t
C
t
=
2
( )
( )
a
aa
C
t
t
ρ
=
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for the exact resonance
Rabi frequency
oscillations
between 0 and 1
0
∆ =
(
2
2
1
2
( )
cos
a
C
t
t
=
Ω
(
2
2
1
2
( )
sin
b
C
t
t
=
Ω
Ω
As the detuning
is increased, the angular frequency at which the population oscillates
increases, since the generalized Rabi frequency is given by
but the oscillation amplitude decreases.
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 Fall '10
 Shalaev
 Rabi, Ω′

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