Sub-pixel detection of laser-induced damage and its growth on fused silica optics using registration residuals

• Published in: Optics express 2021-10, Vol.29 (22), p.35820-35836
• Main Authors: Hallo, Guillaume, Lacombe, Chloé, Parreault, Romain, Roquin, Nadja, Donval, Thierry, Lamaignère, Laurent, Néauport, Jérôme, Hild, François
• Format: Article
• Language: English
• Subjects: Mechanics; Mechanics of materials; Optics; Physics
• ISSN: 1094-4087; 1094-4087
• DOI: 10.1364/OE.433862

Fused silica optics are key components to manipulate high energy Inertial Confinement Fusion (ICF) laser beams but their optical properties can be degraded by laser-induced damage. The detection of laser damage sites is of major importance. The challenge is to monitor damage initiation and growth at sub-pixel scale with highly sensitive measurements. The damage diameter is a widely used indicator to quantify damage growth but its accuracy is strongly dependent on the available image resolution. More recently, it was shown that registration residual maps ( i.e. , gray level differences between two registered images) could also be used to monitor laser-induced damage. In this paper, the performance of both indicators are compared to detect laser damage initiation and growth at high and low image resolutions thanks to a highly instrumented laser setup. The results prove that registration residual maps are more efficient to detect sub-pixel laser damage growth than diameter measurements at a given image resolution. The registration residual maps are therefore a powerful indicator for monitoring laser-induced damage initiation and growth at sub-pixel scale either for laser damage metrology setups, for high energy laser facilities, or other situations where damage is suspected to occur. The accuracy of (laser-induced) damage laws may also be improved thanks to this tool.