ISOMET RFA2 1 Series, Instruction Manual, Page: 13 / 15

13
ISOMET
Basic AO Modulator Parameters
Driver
RF
Intensity
Modulation
Input Laser Beam
1st Order Deflected Beam
0th Order
θ
θ
BRAGG
SEP
The input Bragg angle, relative to a normal to the optical surface and in the plane of deflection is:
θ
BRAGG
=
λ.
fc
2.v
The separation angle between the Zeroth order and the First order is:
θ
SEP
=
λ.
fc
v
Optical rise time for a Gaussian input beam is approximately:
tr
=
0.65.d
v
where: λ = wavelength
fc = centre frequency
v = acoustic velocity of interaction material = 5.5mm/usec (Ge)
= 5.7mm/usec (Quartz)
= 5.96mm/usec (Fused Silica)
d = 1/e
2
beam diameter
Figure 7. Modulation System