THORLABS BC207UV, Руководство по эксплуатации

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BC207 Series
Chapter 6: Operation Instructions
Rev: 8.1, 10-Jan-2022
Page 120
© 2022 Thorlabs
the actual beam width. This leads to an increased M².
q
M² is smaller than 1.0
M² values < 1.0 are non-physical but may be due to
· A Calculation Area that is too small (Clip Level too high - see M2 Settings )
· The accuracy of the measured result. A error of 5% should be considered.
· The wavelength setting was not made properly. Set the wavelength to the correct value;
M² results will be corrected without running a new measurement.
q
The beam profile looks distorted (particularly, at the end positions of the stage).
Even if a laser is expected to produce a Gaussian beam with M² = 1.0, the beam still can be in-
fluenced by every optical element between laser and Beam Profiler. For instance, a focusing
lens could be mounted with a tilt or could produce a height distortion which results in optical ab-
errations and reduced beam quality.
Filters and mirrors may impact on the beam profile as well in the case that surfaces are con-
taminated. Clean surfaces according to manufacturer's instructions.
q
Error message
"The M2 Measurement has been aborted: Insufficient beam diameter variation over the selec-
ted scan range."
The software could not locate sufficient measurement points within the doubled Rayleigh
Length.
· Extend the Measurement Range .
· Select a focusing lens with a shorter focal length.
· Rule of the thumb: the beam diameter variation within the scan range should not run be-
low a ratio of 1:2.5 at least at one side of the beam waist - see the example below.
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