© 2011 Thorlabs
114 Thorlabs Beam 4.0
M²
Mean M² value (arithmetic average of M² X' and M² Y')
M² X' and M² Y'
M² value for X' or Y' axis, respectively, calculated from hyperbolic fit.
Beam Waist Postion X' (Y')
Z position of the beam waist (smallest beam diameter). This is the calculated beam
waist position in mm derived from the curve fit. This value may differ from the
position where the smallest beam width was measured.
Beam Waist Diameter X' (Y')
Beam diameter in X' and Y' direction in focal point. This is the calculated minimum
beam diameter in µm derived from the curve fit. This value may differ from the
smallest measured beam width.
Rayleigh Length X' (Y')
Rayleigh length is the calculated distance from the beam waist position in mm
derived from the curve fit where the beam diameter is 2 times wider than the waist
diameter. See also chapter M2 Theory .
Divergence Angle
Divergence angle of the focused beam is explained in chapter M2 Theory .
Waist Asymmetry
Waist asymmetry stands for the ellipticity at the waist position. It results from the
waist diameters in both X' and Y' directions. A waist asymmetry of 1.0 indicates a
round beam spot.
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