OPHIR BeamSquared, User Manual

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The basic layout of the four-cuts method applied to a beam caustic plot in both the X and Y axes is shown.
When to use the Four-Cuts method 4.1.3.1
The Four-Cuts method may be employed when you have the following prior knowledge of the beam:
 The beam caustic shows little to no astigmatism.
 Or, if astigmatism is present, the X and Y divergence values are somewhat similar so as to keep the 3
data points beyond the Rayleigh range of both caustics.
In all cases, the user must have a general knowledge of approximately where the focused waists are located
and the Rayleigh lengths. A standard M
2
measurement should be performed on the actual, or similar, beam to
obtain this information.
Four-Cuts on Two Axes 4.1.3.2
BeamSquared always treats lasers as if they have two
orthogonal axes. Because of this, the Four-Cuts
method is expanded further and computes results
separately along the X and Y axes.
This figure shows how the two axis samples are
taken. In this example, the beam has little
astigmatism and the divergence is similar in each
axis. The z1, z2, and z3 cuts are placed beyond the
Rayleigh regions and apply the ZRY boundary on the
left and the ZRX boundary on the right.
The z4 and z5 samples represent the computed X and
Y waist locations, respectively. The z6 location is at
the lens focal length.
When z2 and z3 are placed close together without