NTEGRA Spectra Probe NanoLaboratory. SNOM Measuring Head. Instruction Manual
Tuning position of the laser beam
1. In the Auxiliary Operations Area (accessible through the button at the right top of
the Program window), select the
Scheme tab to open the block scheme.
2. Click the secondary mouse button on the button of the scheme window. In
the popped-up list (Fig. 4-15
) , select Save to lock the position of the Z-section of the
scanner.
Fig. 4-15. Selecting the Save item
NOTE. Be aware that leaving the probe in the
Save
state for long time is
risky because the probe can be damaged due to the scanner drift.
3. Turn the turret of exchangeable mirrors to position M0 (totally reflecting mirror). The
laser beam will fall onto the probe and then, after passing the aperture, onto the
sample.
4. Gradually increase the PMT control voltage (PMT1 parameter) until one of the
following events occurs:
- the PMT control voltage achieves the level of 1250 V;
- modulus of the PMT output achieves the level of 1 V.
Monitor the PMT output on the software oscilloscope (Ext2 signal).
The PMT control voltage is adjusted properly if the PMT output changes with turning
the laser beam on and off. The PMT output is expected to be ∼0 V with the exit laser
shutter closed and to be ∼1 V with the shutter open.
5. Perform scanning-by-laser of the probe surface around the aperture. First, scan a
larger area (of size, for instance, 8×8 µm) and then repeat with a smaller area (of size,
for instance, 3×3 µm).
6. Aim the laser beam at the center of the probe aperture by placing the
marker to
the position of the maximal PMT output (Fig. 4-16). Monitor the PMT output on the
software oscilloscope.
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