Parametric study of laser-induced surface damage density measurements: Toward reproducibility

Abstract

In the range of nanosecond pulse lengths, the mechanisms of surface laser damage to dielectric materials are still unclear. A large amount of experimental and theoretical work has been performed over recent years. In order to test theoretical predictions and compare experimental results, reproducibility is essential whatever the beam parameters and experimental conditions. The rasterscan procedure, previously developed to test large components, is an efficient method that allows measuring extremely low surface damage site density (until 0.01 site/cm2 for large optics). In this paper, we show that by suitable data reduction, error bar calculation, and attention paid to beam analysis, laser-induced surface damage density of fused silica optics can be measured with high accuracy and repeatability in the range of pulse durations from 2 to 16 ns. This procedure provides a straightforward means of comparing the experimental results obtained from several facilities using different lasers.

Damage growth in fused silica optics at 351 nm: refined modeling of large-beam experiments

“…Bold squares are very close to this line, meaning that the growth behavior can be described in average by a unique value at a given fluence. A growth threshold around 5 J/cm 2 is deduced from this experiment; it corresponds to the threshold previously reported by several authors [4][5][6][7][8][9][10][11][12][13][14][15][16]. Shot after shot, damage sites are bigger and bigger, but for a given laser energy deposition, the stresses developed by the pressure pulse remain equal for longer circumferential and radial cracks that are more numerous too.…”

“…Values of the coefficient C are reported in the insert for each size bin. The dashed line is the standard behavior from literature [4][5][6][7][8][9][10][11][12][13][14][15][16] Refined modeling of large-beam experiments 523…”

“…The characteristics of this laser are quite similar to high-power lasers such as LMJ and NIF; let us mention the front-end, the amplification stage, the spatial filters and the frequency converter crystals. Then laser damage measurements taken with this system should be representative of the damage phenomenon on highpower lasers.The metrology is very close to small beam metrology [12]: Energy, temporal and spatial profiles are recorded. For the latest, a charge-coupled device (CCD) camera is positioned at a plane optically equivalent to that of the sample (the main characteristics of the laser and measurement principles are reported in Ref.…”

Sub-picosecond laser induced damage test facility for petawatt reflective optical components characterizations

“…Figure 7(b) evidences nodule ejections, embedded in the HR stacks during the coating with delamination of the top layers: a location of an initiator nodule is shown. Gallais et al [12] studied the strong enhancement of the electric field caused by silica microspheres of one determined size embedded in HR coatings and exhibit the behavior of individual nodular sites under sub-picosecond irradiations in function of the excitation fluence. They observed one typical morphology.…”

L’endommagement des optiques du LMJ : problématique, mécanismes et métrologie

“…Ceux-ci sont basés sur le nombre de dommages révélés lors du test. Cette démarche permet de s'assurer de la répétabilité de la mesure et a été mise en oeuvre pour comparer des résultats obtenus sur différentes installations [7]. Cette procédure est utilisée pour la mesure de densités surfaciques de dommages et aussi pour la détermination des densités volumiques dans le cas d'un endommagement préférentiel dans la matière comme généralement observé pour les cristaux [8].…”