Diffractive Effects in the Determination of Damage Thresholds Using Focused Top Hat Beams

Report No. ARL-TN-200
Authors: Timothy M. Pritchett
Date/Pages: April 2003; 12 pages
Abstract: An accurate determination of damage thresholds for focal plane elements must correctly account for diffractive effects. This technical note reviews the physics of Fraunhofer diffraction of a top hat beam. It presents a new result, accurate to second order in the subtended solid angle, for the encircled energy. It describes in detail the computation of peak and average fluences in the presence of diffraction, and it includes a compilation of practical formulae for workers measuring damage threshold fluences.
Distribution: Approved for public release
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Last Update / Reviewed: April 1, 2003