Evaluation of UV absorption coefficient in laser-modified fused silica

Negres, Raluca A.; Burke, Michael W.; Sutton, Steven B.; DeMange, P.; Feit, Michael D.; Demos, Stavros G.

doi:10.1063/1.2472775

Cited by 23 publications

(11 citation statements)

References 17 publications

(14 reference statements)

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“…22,23 Unlike those located in surfaces, wherein silicon remains regularly coordinated, a 2-membered ring in the irradiated bulk usually contains a Si 5 defect. This unique observation indicates that the formation of such 2-membered rings is caused by laser-induced Si 5 (not the native ones), which divided the network rings into smaller ones, resulting in small Si-O-Si bond angles and thus decreased Si-Si pair distances. However, some experiments suggested that the Si-O-Si bond angles will increase after 355-nm irradiation.…”

Section: -3mentioning

confidence: 91%

“…18 bonded to 3 Si atoms) appear and exhibit a comparable growth rate to Si 5 for the first 400 excitations. In previous studies, Si 5 are believed to be native defects in fused silica, and TBO are hypothesized as intermediate products of silicon oxidation during the formation of the amorphous network. 19 For the case of UV-laser radiation, Si 5 and TBO correspond preliminarily to an oxygen-excess and oxygen-deficiency environment, respectively, which may generate Frenkel-type defects as reported elsewhere.…”

Section: -3mentioning

confidence: 99%

“…3,4 It is believed that low fluence laser can induce irreversible structural changes without destroying material integrity. 5 In this work, molecular dynamics (MD) simulations were performed to present evidence that silica structure in both short and medium ranges is directly modified by UV-induced defects.…”

confidence: 99%

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UV-induced modification of fused silica: Insights from ReaxFF-based molecular dynamics simulations

Tian

et al. 2016

AIP Advances

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Atomic structural modification and defect processes of fused silica resulting from UV-laser irradiation are studied by a combination of molecular dynamics (MD) simulations and the Reactive Force Field (ReaxFF). Bond state transitions by laser excitation are modeled as the result of localized recoils during energy deposition. Computations of pair distribution functions and bond angle distributions of the irradiated structure reveal that fused silica undergoes significant changes in terms of Si-O, Si-Si pair distances and Si-O-Si bond angles, which are attributed to the formation of silicon and oxygen coordination defects. It is found that nonbridging oxygen is responsible for the decreased Si-O bond length, while laser-induced five-coordinated silicon leads to small Si-O-Si bond angles in 2-membered rings.

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Section: -3mentioning

confidence: 91%

Section: -3mentioning

confidence: 99%

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UV-induced modification of fused silica: Insights from ReaxFF-based molecular dynamics simulations

Tian

et al. 2016

AIP Advances

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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 ns laser irradiation [1][2][3][4][5][6]. 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][10]. Although various models regarding the processes involved during a surface damage event have been proposed based on post-mortem examination of the crater characteristics for various laser parameters, there are only limited experimental studies that capture the dynamic processes during a damage event [11][12][13].…”

Section: Introductionmentioning

confidence: 99%

Imaging the early material response associated with exit surface damage in fused silica

2010

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The processes involved at the onset of damage initiation on the surface of fused silica have been a topic of extensive discussion and thought for more than four decades. Limited experimental results have helped develop models covering specific aspects of the process. In this work we present the results of an experimental study aiming at imaging the material response from the onset of the observation of material modification during exposure to the laser pulse through the time point at which material ejection begins. The system involves damage initiation using a 355 nm pulse, 7.8 ns FWHM in duration and imaging of the affected material volume with spatial resolution on the order of 1 µm using as strobe light a 150 ps laser pulse that is appropriately timed with respect to the pump pulse. The observations reveal that the onset of material modification is associated with regions of increased absorption, i.e., formation of an electronic excitation, leading to a reduction in the probe transmission to only a few percent within a time interval of about 1 ns. This area is subsequently rapidly expanding with a speed of about 1.2 µm/ns and is accompanied by the formation and propagation of radial cracks. These cracks appear to initiate about 2 ns after the start of the expansion of the modified region. The damage sites continue to grow for about 25 ns but the mechanism of expansion after the termination of the laser pulse is via formation and propagation of lateral cracks. During this time, the affected area of the surface appears to expand forming a bulge of about 40 µm in height. The first clear observation of material cluster ejection is noted at about 50 ns delay.

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“…In addition, laser systems designed to achieve laser-driven inertial confinement fusion operate near the LIB threshold of their component optics. LIB, which has shown to lead to modification of the electronic and structural properties of the host material [1][2][3][4][5][6][7], can eventually lead to the formation of a damage site. Post-mortem characterization of laser-induced damage is widely used and employs various imaging tools, for example scanning and transmission electron microscopies [5], white light scattering and photoluminescence microscopies [1,2], and optical coherence tomography [1] to name a few.…”

Section: Introductionmentioning

confidence: 99%

Time-resolved imaging of material response following laser-induced breakdown in the bulk and surface of fused silica

et al. 2010

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Optical components within high energy laser systems are susceptible to laser-induced material modification when the breakdown threshold is exceeded or damage is initiated by pre-existing impurities or defects. These modifications are the result of exposure to extreme conditions involving the generation of high temperatures and pressures and occur on a volumetric scale of the order of a few cubic microns. The response of the material following localized energy deposition, including the timeline of events and the individual processes involved during this timeline, is still largely unknown.In this work, we investigate the events taking place during the entire timeline in both bulk and surface damage in fused silica using a set of time-resolved microscopy systems. These microscope systems offer up to 1 micron spatial resolution when imaging static or dynamic effects, allowing for imaging of the entire process with adequate temporal and spatial resolution. These systems incorporate various pump-probe geometries designed to optimize the sensitivity for detecting individual aspects of the process such as the propagation of shock waves, near-surface material motion, the speed of ejecta, and material transformations. The experimental results indicate that the material response can be separated into distinct phases, some terminating within a few tens of nanoseconds but some extending up to about 100 microseconds. Overall the results demonstrate that the final characteristics of the modified region depend on the material response to the energy deposition and not on the laser parameters.

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Evaluation of UV absorption coefficient in laser-modified fused silica

Cited by 23 publications

References 17 publications

UV-induced modification of fused silica: Insights from ReaxFF-based molecular dynamics simulations

UV-induced modification of fused silica: Insights from ReaxFF-based molecular dynamics simulations

Imaging the early material response associated with exit surface damage in fused silica

Time-resolved imaging of material response following laser-induced breakdown in the bulk and surface of fused silica

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