DAZZLER
TM
system manual Part I : installation & operation 2.2
2.2 Key parameters
In this section, the reader will find the most important parameters describing the acousto-optic
interaction.
2.2.1 Diffraction efficiency
The general formula giving the output optical intensity
1
I
out
(ω) in the plane wave and
monochromatic approximation is [4]:
I
out
(ω) = I
in
(ω)η(ω) (2.12)
with:
η(ω) =
π
2
4
P
P
0
sinc
2
s
π
2
4
P
P
0
+
∆k L
2
2
(2.13)
where:
• I
in
(ω) is the input optical intensity,
• P the actual acoustical power density,
• ∆k =
~
k
diff,e
−
~
k
in,o
−
~
k
ac
.~u
ac
is the phase matching mismatch along the acoustic prop-
agation direction,
• L is the crystal length along the acoustic propagation direction,
• P
0
is a characteristic acoustic power given for the Dazzler
TM
HR models:
P
0
= 3.7 · 10
6
·
λ
L
2
in W/mm
2
(2.14)
– For L = 25 mm, λ = 800 nm, P
0
= 3.8 mW/mm
2
– For L = 45 mm, λ = 1 µm, P
0
= 1.8 mW/mm
2
When P = P
0
and ∆k = 0, the transfer coefficient to the diffracted wave is 100%:
I
out
(ω) = I
in
(ω)
.
For sufficiently low values of P compared to P
0
, the AOPDF response is linear with P and:
I
out
(ω) = I
in
(ω)
π
2
4
P
P
0
sinc
2
∆k L
2
(2.15)
1
Unit is W/cm
2
.
V3.00 - 8
th
April 2019 (ContentsTable) (FiguresTable) 10/94
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