FASTLITE DAZZLER - Launching a Waveform; Examples of Experimental Setup

DAZZLER
TM
system manual Part I : installation & operation 2.2
2.2.2 Spectral resolution
We now assume a perfect phase-matching for a set of frequencies and directions. If the in-
put optical frequency is varied while all the other parameters are kept constant (directions,
polarizations, acoustic frequency) then ∆k L 6= 0 and the diffraction efficiency drops (sinc
2
function).
For P < P 0
δλ
1/2
=
0.8 · λ
2
δn · L
≈ 8.9 ·
λ
2
L
(2.16)
δn being the index difference between ordinary and extraordinary waves on the propagation
axis in the crystal. For HR Dazzler
TM
systems,
• For L = 25 mm, λ = 800 nm, δλ
1/2
= 0.23 nm
• For L = 45 mm, λ = 1 µm, δλ
1/2
= 0.20 nm
2.2.3 Number of independent programming points
If ∆λ is the bandwidth of input optical signal in wavelengths, the number of independent
programming points of the AOPDF is:
N =
∆λ
δλ
1/2
= 1.25 · δn · L ·
∆λ
λ
2
≈
L
8.9
·
∆λ
λ
2
(2.17)
• For L = 25 mm, ∆λ = 100 nm@800 nm, N = 439
• For L = 25 mm, ∆λ = 300 nm@800 nm, N = 1318
• For L = 45 mm, ∆λ = 20 nm@1 µm, N = 101
2.2.4 Input beam angular aperture (divergence)
With a WB crystal cut, the divergence of the input beam must be inferior to:
δθ
1/2
= n
0
· (δθ
0
)
1/2
= 2.47 · (
δλ
λ
)
1/2
= 22 ·
λ
L
(2.18)
• For L = 25 mm, λ = 800 nm, δθ
1/2
= 0.04
◦
• For L = 45 mm, λ = 1 µm, δθ
1/2
= 0.028
◦
The input beam divergence degrades the resolution.
2.2.5 Acoustic power density to drive n points
The acoustic power density needed to drive the N independent spectral points of subsec-
tion 2.2.3 for a total diffraction of these points is:
P
N
= N · P
0
= 4.15 · 10
5
·
∆λ
L
in W/mm
2
(2.19)
• For L = 25 mm and ∆λ = 100 nm, P
N
= 1.66 W/mm
2
• For L = 45 mm and ∆λ = 20 nm, P
N
= 0.18 W/mm
2
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