THORLABS M2MS, Operating Manual

Page: 109 / 167

BP209 Series 7 Operation Instructions
Rev: 8.1, 14-Feb-2022 © 2022 Thorlabs Page 107
Hyperbolic Fit Y'
These values can also be found in the listing of the complete results next to the diagram:
M² X' and M² Y' are the M² value for X' / Y' axis, calculated from the hyperbolic fit of the meas-
ured data points.
Rayleigh Length X' (Y') is the calculated distance [mm] from the beam waist position X' (Y') to
the position, where the beam diameter of the appropriate axis is Ö 2 times larger than the waist
diameter. See also section M2 Theory .
Waist Diameter X' (Y') is the beam diameter in the X' (Y') direction at the focal point. This is
the calculated minimum beam diameter [µm], derived from the curve fit. This value may differ
from the smallest measured beam width.
Waist Asymmetry stands for the ellipticity at the waist position and is calculated by taking the
ratio of the waist diameters in both X' and Y' directions. A waist asymmetry of 1.0 indicates a
round beam spot.
Waist Position X' (Y') Z position of the beam waist (smallest beam diameter). This is the calcu-
lated beam waist position in mm derived from the curve fit. This value may differ from the posi-
tion where the smallest beam width was measured.
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