MesaPhotonics VideoFROG FROGscan, User Manual

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Chapter 3. Program Panels
Page 26 FROGSCAN USER’S MANUAL 09/07/2018 Vs 003
3.4.1 Automated Crystal Tilt Function
In instruments with Autotilt function, the crystal tilt settings are entered in the Data Acquisition Panel. The
crystal tilt is controlled using a direct drive, five pole stepper motor designed specifically for
microstepping. Two pins and an opto-interrupter are used to home the crystal when the software is first
started, or when the Change Crystal button is clicked.
The angle of the crystal tilt can be changed in the Left Control Panel (Figure 12) by either clicking on the
spinner controls or by entering numbers into the display. The values are saved when the software is
exited and the crystal is tilted using the saved settings when the program is restarted.
Crystal Tilt ̶ Displays the external crystal tilt from vertical in degrees.
Fast ̶ Tilts the crystal by 1 degree for each click on the spinner.
Slow ̶ Tilts the crystal by 0.1 – 0.2 degrees.
Stationary ̶ The crystal sits at only one position.
Xtal Scanning – When a crystal is too thick to phase match all of the wavelengths present in the pulse at
a single angle, it acts like a wavelength filter that limits the bandwidth of the measured pulse. When a
thinner crystal is not available or would reduce the signal to an undetectable level, the crystal can be tilted
while the data is being acquired between scans. VideoFROGscan takes an image for each crystal tilt
angle, and sums all of these images together to form the FROG trace used in the retrieval.
After the angular positions are recorded in the Left Control Panel, the crystal tilt scan is activated when
the Xtal Scanning button in the left Panel is clicked. A popup window opens in the Data Acquisition Panel
in which the Tilt Points are entered (Figure 13).
Crystal Tilt Control
Xtal tilts per Frame – Crystal tilts required to complete a scan so all of the different frequencies in the
pulse are phase matched.
Xtal Angles – Records the angle of the crystal.
Once the number of tilts is set, the actual crystal tilts can be saved in the XFROG Pulse Server and File
Location selected (see above).
Figure 12. Crystal Tilt functions in the Left Control Panel.
Figure 13. Popup window that appears after Xtal Scanning was
clicked.