Laser-induced damage tests based on a marker-based watershed algorithm with gray control

Abstract

An effective damage test method based on a marker-based watershed algorithm with gray control (MWGC) is proposed to study the properties of damage induced by near-field laser irradiation for large-aperture laser facilities. Damage tests were performed on fused silica samples and information on the size of damage sites was obtained by this new algorithm, which can effectively suppress the issue of over-segmentation of images resulting from non-uniform illumination in darkfield imaging. Experimental analysis and results show that the lateral damage growth on the exit surface is exponential, and the number of damage sites decreases sharply with damage site size in the damage site distribution statistics. The average damage growth coefficients fitted according to the experimental results for Corning-7980 and Heraeus-Suprasil 312 samples at 351 nm are 1.10 ± 0.31 and 0.60 ± 0.09, respectively.

Growth of Laser Damage in Fused Silica and CaF2 Under 263-nm Laser Irradiation

“…A comparison of these two materials is presented in Table 1. The initial thresholds for the two samples are also listed in Table 1 [5]. We observe that the initial damage threshold of CaF 2 of ˜5.1 J/cm 2 as well as the growth threshold of CaF 2 were higher than those of fused silica (˜1.77 J/cm 2 ).…”

“…Materials commonly used in high-power laser systems include fused silica, fluoride, and k9. k9 has a lower transmittance in the ultraviolet band, whereas fused silica and CaF 2 are increasingly used in deep-ultraviolet optical components because of their excellent optical and mechanical properties in the ultraviolet band [4][5][6]. Methods have been proposed for improving the laser damage threshold of optical components [7,8].…”

Status and development of high-power laser facilities at the NLHPLP

“…(5) The compact FOA was designed and constructed using a wedged focal lens and specific stray light management [79, 80] . Due to the limited space of the target area, the focal length of the target lens in the SG-II UP laser facility was chosen to be 2.2 m. This relatively short focal lens is shorter than might otherwise be necessary to achieve a fixed harmonic separation, leading to a higher B-integral value for a given laser intensity.…”