© 2011 Thorlabs
88 Thorlabs Beam 4.0
increases with M
2
. Therefore, the translation range needs to be longer for bad beam
quality (K<<1, M
2
>>1).
See Focal and stage length calculation for details.
Diagram B shows the minimal required stage length for M
2
=1 depending on the
expected waist diameter:
Diagram B
Select your operating wavelength at the x-axis of the diagram B and go up to the
curve representing your expected waist diameter. Then read out the minimal
required translation range at the vertical axis. Multiply this result with the highest
expected M
2
value of your laser source and round it up to the next available
translation stage length (150 or 300 mm). Please note this length is a minimum
requirement for M
2
detection.
As a disadvantage, for each application the short stage carrying the Beam Profiler
needs to be well positioned according to the beam waist position. Therefore, the
longer stage length of 300 mm is advisable for universal setups which are ready to
use for various laser types, beam diameters, wavelengths, M
2
values and focal
lengths. Also, the entire diverging process on both sides of the beam waist can be
analyzed without the need to relocate a shorter stage to the new focus position.
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