© 2011 Thorlabs
144 Thorlabs Beam 4.0
These distortions lead to higher divergence and wider beam waist compared to
Gaussian beams when focused using the same lens. As a result the achievable max.
power density is reduced.
Comparison of propagation between fundamental mode TEM
00
(ideal
Gaussian beam) and mode mixture beam
With a given divergence angle (i.e. knowing the focus of the lens) the fundamental
mode alone produces the smallest (theoretical limited) beam waist (green curve). If
beam quality gets worse (red curve) the beam waist becomes wider than before. If
divergence is fixed, beam waist is enlarged by the factor M
2
and the appropriate
power density at z
0
is reduced by a factor (M
2
)
2
.
The Rayleigh length may also be influenced due to the changed beam propagation
curve.
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