Growth of laser damage in fused silica: diameter to depth ratio

Norton, Mary A.; Adams, John J.; Carr, C. W.; Donohue, Eugene E.; Feit, Michael D.; Hackel, Richard P.; Hollingsworth, William G.; Jarboe, J.; Matthews, Manyalibo J.; Rubenchik, Alexander M.; Spaeth, M. L.

doi:10.1117/12.748441

Cited by 43 publications

(24 citation statements)

References 5 publications

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“…They show deoxidized, densified silica, and fractures, both lateral cracks, and deep, conical cracks. 36,37,38 We propose that Conical Fractures are the essential feature. This model is currently under development : here are the first results.…”

Section: Damage Growthmentioning

confidence: 99%

Fracture related initiation and growth of surface laser damage in fused silica

Bercegol

Grua

2008

Laser-Induced Damage in Optical Materials: 2008

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This paper deals with the relation between fracture mechanics and 355 nm laser damage at the surface of fused silica. It is organized in 3 parts. First, we discuss about the link between cracks and laser initiation of surface damage. A 1D model was proposed last year to explain how a nanometer wide, clean, uncontaminated crack could trigger a macroscopic damage event. Here, using the model, we try to express a damage criterion able to reproduce experimental features.In a second part, we consider the relationship between laser damage and mechanical damage by indents or impacts. From Auerbach's law, it is straightforward to derive an energy density threshold for Hertzian crack initiation. With the laser fracture interaction model, a laser fluence threshold of cone crack formation can be calculated. When cone cracks are present, a series of shot at moderate fluence will increase their length exponentially. This is a possible explanation for exponential damage growth at the exit surface of fused silica.

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Section: Damage Growthmentioning

confidence: 99%

Fracture related initiation and growth of surface laser damage in fused silica

Bercegol

Grua

2008

Laser-Induced Damage in Optical Materials: 2008

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“…On the side views, subsurface cracks corresponding to this open crack can be seen but also more lateral cracks. These lateral cracks are similar to the ones observed by Norton [13] and Wong [7]. The damage depth (h) is defined as the distance from the optical surface to the bottom of the deepest visible crack.…”

Section: Confocal Laser Scanning Microscopymentioning

confidence: 87%

Characterizations of UV-laser damage on fused silica surfaces

et al. 2008

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Significant improvement in polishing processes of fused silica optical components, has increased optics lifetime at the wavelength of 351 nm. Nonetheless, for large laser operation facilities like the Laser MegaJoule (LMJ), zero defect optics are not yet available. Therefore a damage mitigation technique has been developed to prevent the growth of initiated damage sites: this technique consists in a local melting and evaporation of silica by CO2 laser irradiation on the damage site. Because of the difficulty to produce efficient mitigated sites with large depth, the initial depth of damage to mitigate is a critical issue. An aim of our work was to determine the real extension of the damage site (including fractures) for different laser pulse durations between 3 ns and 16 ns and at different laser fluences. The fractures are nondetectable in conventional microscopy. The depth of the damage can thus be underestimated. Hence confocal microscopy, was used to observe these sub-surface fractures and to measure precisely the depth of damage. Results show that the damage is 2 to 4 times wider than deeper and this ratio is independent of the pulse duration and of the fluence. With this new information, the mitigation process can now be optimized.

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“…Damage initiation sites are typically on the order of 10 μm in diameter, depending on the laser pulse length, but tend to grow exponentially under subsequent laser irradiation [1][2][3][4][5]. Microscopic examination of these sites reveals the formation of a damage crater containing modified material believed to be the result of exposure to high pressures and/or temperatures, as well as cleaved surfaces and cracks [6][7][8][9].…”

Section: Introductionmentioning

confidence: 98%

Imaging system to measure kinetics of material cluster ejection during exit-surface damage initiation and growth in fused silica

2009

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Laser-induced damage on the surface of optical components typically is manifested by the formation of microscopic craters that can ultimately degrade the optics performance characteristics. It is believed that the damage process is the result of the material exposure to high temperatures and pressures within a volume on the order of several cubic microns located just below the surface. The response of the material following initial localized energy deposition by the laser pulse, including the timeline of events and the individual processes involved during this timeline, is still largely unknown. In this work we introduce a time-resolved microscope system designed to enable a detailed investigation of the sequence of dynamic events involved during surface damage. To best capture individual aspects of the damage timeline, this system is employed in multiple imaging configurations (such as multi-view image acquisition at a single time point and multi-image acquisition at different time points of the same event) and offers sensitivity to phenomena at very early delay times. The capabilities of this system are demonstrated with preliminary results from the study of exitsurface damage in fused silica. The time-resolved images provide information on the material response immediately following laser energy deposition, the processes later involved during crater formation or growth, the material ejecta kinetics, and overall material motion and transformation. Such results offer insight into the mechanisms governing damage initiation and growth in the optical components of ICF class laser systems.

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Growth of laser damage in fused silica: diameter to depth ratio

Cited by 43 publications

References 5 publications

Fracture related initiation and growth of surface laser damage in fused silica

Fracture related initiation and growth of surface laser damage in fused silica

Characterizations of UV-laser damage on fused silica surfaces

Imaging system to measure kinetics of material cluster ejection during exit-surface damage initiation and growth in fused silica

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