5
ISOMET
3.4
Adjustment of the RF output power is best done with amplifier connected to the acousto-optic
modulator.
3.5
The optimum RF power level required for the modulator to produce maximum first
order intensity will be different at various laser wavelengths. Applying RF power in
excess of this optimum level will cause a decrease in first order intensity (a false
indication of insufficient RF power ) and makes accurate Bragg alignment difficult. It
is therefore recommended that initial alignment be performed at a low RF power level.
3.6
Set the input power level to give approximately 4W per output.
3.7
Apply DC power to the amplifier.
3.8
Apply a constant RF input to the input SMA connector of the RFA0110-2 (ref: 3.7)
Input the laser beam toward the centre of either aperture of the AO device. Ensure the polarization is
vertical with respect to the base and the beam height does not exceed the active aperture height of
the AOM/AOD.
Start with the laser beam normal to the input optical face of the AOD and very slowly rotate the AOD
(see page 12 for configurations.)
3.9
Observe the diffracted first-order output from the acousto-optic modulator and the undeflected
zeroth order beam. Adjust the Bragg angle (rotate the modulator) to maximise first order
beam intensity.
3.10
After Bragg angle has been optimized, slowly increase the RF input power until maximum first
order intensity is obtained. This should occur at < 6W per output for the D1340-aQ110-5 at
355nm.
