FASTLITE DAZZLER User Manual

chapter 2
Physics
The Dazzler system is an Acousto-Optic Programmable Dispersive Filter (AOPDF). This chap-
ter briefly describes the physical principles of the device. All the figures illustrate the standard
AOPDFs configuration based on a Paratellurite crystal (TeO2).
2.1 AOPDF principle
In an AOPDF, the pulse shaping mechanism arises from a copropagative interaction between
a polychromatic acoustic wave and a polychromatic optical wave in a birefringent crystal with
acousto-optic properties. When the right physical conditions are met (the so-called phase-
matching conditions), the input optical and acoustic beams interact and give rise to a new
optical beam, which is referred to as the diffracted beam. Section 2.1.1 describes the phase-
matching conditions whereas section 2.1.2 details one special feature of the acousto-optic in-
teraction in an AOPDF: the collinearity in terms of Poynting vectors. Section 2.1.3 gives more
details on the pulse-shaping mechanism.
2.1.1 Phase-matching conditions
As for all three-wave mixing processes, the phase-matching condition for monochromatic plane
waves is defined by two conditions:
• wave-vector conservation (momentum conservation)
• frequency conservation (quantum energy conservation)
Mathematically, these conditions can be expressed as:
(
~
k
diff
(ω
opt,diff
) =
~
k
in
(ω
opt,in
) +
~
k
ac
(ω
ac
)
ω
opt,diff
= ω
opt,in
+ ω
ac
(2.1)
where (
~
k
diff
, ω
opt,diff
), (
~
k
in
, ω
opt,in
) and (
~
k
ac
, ω
ac
) stand for the wave-vectors and angular frequen-
cies of the optical diffracted beam, optical input beam and acoustic beam respectively.
For the standard AOPDFs, based on TeO
2
, the input optical beam is usually ordinary polarized,
the diffracted beam is extraordinary polarized and the acoustic beam is a shear wave.
Since the velocity of sound in crystals is much lower than the velocity of light, the acoustic
frequency is completely negligible with respect to that of light (ω
ac
 ω
opt
) so that the phase-
matching condition reads finally:
6

FASTLITE DAZZLER Specifications

General

Brand	FASTLITE
Model	DAZZLER
Category	Measuring Instruments
Language	English