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Proceedings Paper

Beam characterization: application to the laser damage threshold
Author(s): Jean Hue; Jean Dijon; Pierre Garrec; Guillaume Ravel; Ludovic Poupinet; Philippe Lyan
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Paper Abstract

The laser damage threshold determination is linked to many factors as the damage criteria, the test conditions, etc. Among them, the spatial beam characterization as well as the power or the energy in the beam plays a key role. Indeed, an appropriate value has to be assigned to each tested site. This number is important to certify a component or to compare the components. This paper is focused on determining the beam parameters for 2 kinds of laser damage. The first part addresses the peak fluence measurement on YAG laser damage test facilities. The proposed method is applied to stable laser. Stable lasers mean the spatial profile is similar during the experiments. Before the laser damage tests, the spatial beam is visualized with a CCD camera. Them, the spatial beam profile is cautiously processed to extract the relation between the peak fluence and the energy, which is easy to measure in real time. This method is illustrated at 1064 nm. Finally, this procedure is validated on silicon wafer. Indeed, at 1064 nm, the theoretical laser damage threshold of silicon wafer is well known. Furthermore, it is independent of the pulse length in the nanosecond regime. The second part will be shortly devoted to a more specific problem: the CW damage threshold of CO2 mirrors. It has been previously shown that the 'short' term threshold of these cooled components is well described by a critical temperature. Due to the test geometry, the temperature rise is proportional to the beam power divided by a value homogeneous to the beam radius. In this article, it is sown the knife-edged method allows to literally extract the beam size parameter which appears in the theoretical formula of the critical temperature. The beam just needs to have a symmetry of revolution.

Paper Details

Date Published: 7 April 1999
PDF: 12 pages
Proc. SPIE 3578, Laser-Induced Damage in Optical Materials: 1998, (7 April 1999); doi: 10.1117/12.344398
Show Author Affiliations
Jean Hue, CEA-LETI (France)
Jean Dijon, CEA-LETI (France)
Pierre Garrec, CEA-LETI (France)
Guillaume Ravel, CEA-LETI (France)
Ludovic Poupinet, CEA-LETI (France)
Philippe Lyan, CEA-LETI (France)

Published in SPIE Proceedings Vol. 3578:
Laser-Induced Damage in Optical Materials: 1998
Gregory J. Exarhos; Arthur H. Guenther; Mark R. Kozlowski; Keith L. Lewis; M. J. Soileau, Editor(s)

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