Chapter 1. Basic Information
Fig. 1-1. Transmission Illumination Mode
The primary laser beam is focused by the objective on the probe aperture. The sample
surface stays as close to the probe as to be in the near field of the aperture.
Radiation emitted by the aperture and scattered by the sample is collected with the optical
system and directed to the PMT detector. The PMT output serves for formation of the
sample optical bitmap.
The instrument can perform the following scanning modes:
− scanning-by-sample;
− scanning-by-laser.
In the scanning-by-sample mode, the sample is moved in the XY plane with the tubular
XYZ-scanner. It is important for SNOM techniques that the probe aperture stays on the
axis of radiation delivery and detection.
In the scanning-by-laser mode, the sample and the probe are fixed. Scanning is provided
by the mirror scanner of the radiation delivery and recording system.
Scanning-by-laser is used for fine adjustment of the instrument that implies alignment of
directions of the primary beam and of the detector. Analytical measurements use the
mode of scanning-by-sample.
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