THORLABS BC207UV, Operating Manual

Page: 165 / 181

BC207 Series
Chapter 9: Application Note
Rev: 8.1, 10-Jan-2022
Page 158
© 2022 Thorlabs
9.7 Bessel Fit
On of the most important properties of a Bessel beam is that it is non-diffractive. This means,
apart from Gaussian beams, their shape does not change during propagation, and they do not
have a focus in terms of a location with highest intensity along the propagation direction. Its dis-
tribution can be described by a Bessel function of the first kind.
Ideal Bessel beams do not exist, but a good approximation - a Bessel-Gauss beam - can be
achieved by focusing a Gaussian beam using an axicon lens, a narrow annular aperture, or a
axisymmetric diffraction grating. The output of some step index fibers can also have a profile
close to a Bessel beam.
The Bessel fit approximates a given beam profile to a Bessel function distribution.