chapter 3
Installation & setup
This chapter describes the installation of a Dazzler: connections and settings for two typical
experiments. Details will be found in the following chapters.
3.1 Connections
Before starting please verify:
• the input beam diameter (<2.5mm FWHM),
• the input beam polarization: linear, orthogonal to the diffraction plane (see Figure 3.3),
• the input beam energy/power: < 30µJ/pulse for sub-ps pulses, < 100MW/cm
2
for ns
pulses. For other pulse durations please contact Fastlite.
• the trigger signal: 0-4V TTL signal on 50Ω load. Minimum delay before the optical pulse
depends on crystal (≃40-60µs).
The proper synchronization between the acoustic wave and the optical wave is obtained when
the optical pulse goes through the crystal when the acoustic wave is filling the crystal. The
Dazzler TRIGGER has to be fed a logic signal issued from the laser. The rising edge of this
trigger signal occurs Trigger to Laser microseconds before the optic pulse going through the
crystal. This time interval is approximately equal to the acoustic propagation time into the
crystal
1
. The triggering configuration varies with the experimental setup (10Hz, kHz lasers,
100kHz). For operational details see chapter 4.
3.1.1 Connecting the unit and starting the software
1. connect the RF output to the crystal unit,
2. connect the USB A-B cable with ferrites to the host computer,
3. connect the grounding cable to the optical table (section 7.3),
4. install the crystal unit in the beam line. The crystal unit is not symmetric. The input
face is the one close to the ”D” of the ”Dazzler” label. The output face is the one close
to the ”R” of the ”Dazzler” label (Figure 3.3),
5. turn on the power switch on the rear panel of the RF generator. The waveform memory
is zeroed at power on: there is no RF output.
1
The acoustic propagation time depends on the crystal cut and its length. For 25mm long crystals, this time
is 23.6 µs for WB cut, and 32.6 µs for HR cut. This time is called TXtal .
15
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