9
ISOMET
Schematic for an AO modulator with 750c series driver
752c
RF
Intensity
Modulation
(x2 inputs)
Input Laser Beam
1st Order Deflected Beam
0th Order
BRAGG
SEP
The input Bragg angle, relative to a normal to the optical surface and in the plane of deflection is :
BRAGG
=
fc
2.v
The separation angle between the zeroth order and the first order outputs is :
SEP
=
fc
v
Optical rise time for a Gaussian input beam is approximated by :
tr =
0.65.d
v
where :
= wavelength
fc = centre frequency
= see test data sheet
v = acoustic velocity of AO interaction material = 4.21mm/usec (TeO
2
)
= 3.63mm/usec (PbMoO
4
)
= 5.7mm/usec (Quartz)
= 5.96mm/usec (Fused Silica)
d = 1/e
2
beam diameter
Figure 5: Modulation System
