An accurate, repeatable, and well characterized measurement of laser damage density of optical materials

Abstract

Known for more than 40years, laser damage phenomena have not been measured reproducibly up to now. Laser resistance of optical components is decreased by the presence of material defects, the distribution of which can initiate a distribution of damage sites. A raster scan test procedure has been used for several years in order to determine laser damage density of large aperture UV fused silica optics. This procedure was improved in terms of accuracy and repeatability. We describe the equipment, test procedure, and data analysis to perform this damage test of large aperture optics with small beams. The originality of the refined procedure is that a shot to shot correlation is performed between the damage occurrence and the corresponding fluence by recording beam parameters of hundreds of thousands of shots during the test at 10Hz. We characterize the distribution of damaging defects by the fluence at which they cause damage. Because tests are realized with small Gaussian beams (about 1mm at 1∕e), beam overlap and beam shape are two key parameters which have to be taken into account in order to determine damage density. After complete data analysis and treatment, we reached a repeatable metrology of laser damage performance. The measurement is destructive for the sample. However, the consideration of error bars on defect distributions in a series of parts allows us to compare data with other installations. This will permit to look for reproducibility, a necessary condition in order to test theoretical predictions.

Remarkable enhancement in crystalline perfection, second harmonic generation efficiency, optical transparency, and laser damage threshold in potassium dihydrogen phosphate crystals by L-threonine doping

“…From the inertial confinement fusion application point of view there are many studies regarding laser induced damage or LDT of KDP crystals with significant improvements or modifications both in experimental and methodology aspects toward the improvement of their measurements. [17][18][19][20] In the present investigation influence of L-thronine doping in KDP crystals on growth morphology, SHG, and LDT properties have been investigated. Pure and L-threonine ͑LT͒ doped single crystals of KDP were grown by the conventional slow evaporation solution technique ͑SEST͒.…”

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

“…Un exemple de résultat est reporté sur la figure 1. La procédure est décrite dans la référence [6] où une attention particulière est portée sur la détermination d'intervalles de confiance. En effet, les tests étant destructifs, il n'est pas possible de répéter la mesure sur le même composant, ce qui rend difficile la notion de répétabilité mais également la comparaison des mesures entre différentes installations.…”

Correlation between laser-induced damage densities of fused silica and average incubation fluences at 1064 nm in the nanosecond regime

“…Figure 5(a) shows that the difference between damage densities is small (less than a decade, intervals of confidence 4 do not entirely overlap). Nonetheless this difference is much lower than the previous one reported in Fig.…”

“…In most cases, damage density is obtained by means of 1-on-1 1 procedure that measures high damage densities 2,3 and/or rasterscan procedure that measures low ones. 4,5 These two procedures are complementary and permit us to compare the damage resistance of several optical components. This statistical study is useful when considering the effects of beam and pulse parameters leading to a qualitative comparison without physical interpretation.…”