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Beamage-M² User Manual Revision 6 36
6. M² MANUAL METHOD
The Manual M 2 method is the simplest of the M 2 measurement methods and is ideal for stable laser beams.
To manually measure the M
2
factor of your laser, you will need an imaging lens and a system to measure
the distance between the lens and the sensor plane of the camera. Ideally, you should use a graduated
optical rail system to get the most accurate measurement, but a simple ruler or a caliper can be employed.
The optical setup of the Manual M
2
method reimages the laser beam waist and captures different slices of
the laser beam propagation within at least 3 Rayleigh lengths . Here is a simplified setup to measure the M
2
factor. Please make sure to properly attenuate the laser beam before the lens, as the beam power density
will be higher at the waist position, after the lens.
Figure 6-1: Optical setup for the M² measurement
Tips
•
Make sure to place a lens after the beam waist in order to be able to
reimage it.
•
Choose a lens that allows a travel distance that is within your
workable space.
•
You can use laser viewing cards along the z-axis to make sure you
have an appropriate waist and get a rough idea of its position.
•
Align the Beamage and the Z-axis to make sure the laser beam stays
within the sensor perimeter along the entire travel range. Due to
minimal misalignment, the beam might not always be perfectly
centered. Although not ideal, this is not an issue, as long as the beam
stays within the sensor perimeter.