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Experimental Study Of 351 Nm And 527 Nm Laser Initiated Surface Damage On Fused Silica Surfaces Due To Typical Contaminants
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Book Synopsis Experimental Study of 351-nm and 527-nm Laser-initiated Surface Damage on Fused Silica Surfaces Due to Typical Contaminants by : M. A. Johnson
Download or read book Experimental Study of 351-nm and 527-nm Laser-initiated Surface Damage on Fused Silica Surfaces Due to Typical Contaminants written by M. A. Johnson and published by . This book was released on 2004 with total page 10 pages. Available in PDF, EPUB and Kindle. Book excerpt: Optics damage under high-intensity illumination may be the direct result of laser light interaction with a contaminant on the surface. Contaminants of interest are small particles of the materials of construction of large laser systems and include aluminum, various absorbing glasses, and fused silica. In addition, once a damage site occurs and begins to grow, the ejecta from the growing damage site create contamination on nearby optic surfaces and may initiate damage on these surfaces via a process we call ''fratricide.'' We report on a number of experiments that we have performed on fused silica optics that were deliberately contaminated with materials of interest. The experiments were done using 527-nm light as well as 351-nm light. We have found that many of the contaminant particles are removed by the interaction with the laser and the likelihood of removal and/or damage is a function of both fluence and contaminant size. We have developed an empirical model for damage initiation in the presence of contaminants.
Book Synopsis Laser Induced Damage in Optical Materials by :
Download or read book Laser Induced Damage in Optical Materials written by and published by . This book was released on 2007 with total page 760 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Growth of Laser Initiated Damage in Fused Silica at 527 Nm by : J. N. McElroy
Download or read book Growth of Laser Initiated Damage in Fused Silica at 527 Nm written by J. N. McElroy and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The effective lifetime of optics is limited by both laser-induced damage and the subsequent growth of laser initiated damage sites. We have measured the growth rate of laser-induced damage in fused silica in both air and vacuum at 527 nm. For damage on the exit surface, the data shows exponential growth in the lateral size of the damage site with shot number. The exponential growth coefficient depends linearly on the laser fluence. The behavior at the fluence threshold for growth is contrasted to that observed at 351 nm. The growth rate was not significantly affected by either the wavelength of the initiating fluence or the presence of 10 torr of air as compared to vacuum. When the damage is located on the input surface, it has both a higher threshold for growth and does not grow exponentially.
Book Synopsis Laser-induced Damage Initiated on the Surface of Particle Contamination Fused Silica at 1064nm by :
Download or read book Laser-induced Damage Initiated on the Surface of Particle Contamination Fused Silica at 1064nm written by and published by . This book was released on 1998 with total page 51 pages. Available in PDF, EPUB and Kindle. Book excerpt: An experimental study was undertaken to quantify the effects of contamination particles on the damage threshold of laser-illuminated fused silica optics and set cleanliness requirements for optics on the beam line of the National Ignition Facility at Lawrence Livermore National Laboratory. Circular contamination particles were sputter-deposited onto fused silica windows which were then illuminated repetitively using a 1064nm laser. A variety of contaminants were tested including metals, oxides, and organics. Tests were conducted with particles on the input and output surfaces of the window, and the morphological features of the damage were very reproducible. A plasma often ignited at the contamination particle; its intensity was dependent upon the mass of the contaminant. Input surface damage was characteristically more severe than output surface damage. The size of the damaged area scaled with the size of the particle. On a few occasions, catastrophic damage (cracking or ablation of the substrate) initiated on the output surface due to contamination particles on either the input or output surface. From damage growth plots, predictions can be made about the severity of damage expected from contamination particles of known size and material.
Book Synopsis Laser-induced Damage of Fused Silica at 355 and 1065 Nm Initiated at Aluminum Contamination Particles on the Surface by :
Download or read book Laser-induced Damage of Fused Silica at 355 and 1065 Nm Initiated at Aluminum Contamination Particles on the Surface written by and published by . This book was released on 2001 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: 1-[mu]m thick circular dots, 10-250[mu]m dia, were deposited onto 1.14 cm thick fused silica windows by sputtering Al through a mask. Al shavings were also deposited on the windows to investigate effects of particle-substrate adhesion. The silica windows were then illuminated repetitively using a 3-ns, 355 nm and an 8.6-ns, 1064 nm laser. The tests were conducted at near normal incidence with particles on input and output surfaces of the windows. During the first shot, a plasma ignited at the metal particle and damage initiated on the fused silica surface. The morphology of the damage at the metal dots were reproducible but different for input and output surface contamination. For input surface contamination, minor damage occurred where the particle was located; such damage ceased to grow with the removal of contaminant material. More serious damage (pits and cracks) was initiated on the output surface (especially at 355 nm) and grew to catastrophic proportions after few shots. Output surface contaminants were usually ejected on the initial shot, leaving a wave pattern on the surface. No further damage occurred with subsequent shots unless a shot (usually the first shot) cracked the surface; such behavior was mostly observed at 355 nm and occasionally for large shavings at 1064 nm. The size of the damaged area scaled with the size of the particle (except when catastrophic damage occurred). Onset of catastrophic damage on output surface occurred only when particles exceeded a critical size. Damage behavior of the sputtered dots was found to be qualitatively similar to that of the shavings. The artificial contamination technique accelerated the study by allowing better control of the test conditions.
Book Synopsis Growth of Laser Initiated Damage in Fused Silica at 351 Nm by :
Download or read book Growth of Laser Initiated Damage in Fused Silica at 351 Nm written by and published by . This book was released on 2001 with total page 9 pages. Available in PDF, EPUB and Kindle. Book excerpt: The lifetime of optics in high-fluence UV laser applications is typically limited by the initiation of damage and its subsequent growth. We have measured the growth rate of laser-induced damage on fused silica surfaces in both air and vacuum. The data shows exponential growth in the lateral size of the damage site with shot number above a threshold fluence. The concurrent growth in depth follows a linear dependence with shot number. The size of the initial damage influences the threshold for growth; the morphology of the initial site depends strongly on the initiating fluence. We have found only a weak dependence on pulse length for growth rate. Most of the work has been on bare substrates but the presence of a sol-gel AR coating has no significant effect.
Book Synopsis Thin Film Contamination Effects on Laser-induced Damage of Fused Silica Surfaces at 355 Nm by :
Download or read book Thin Film Contamination Effects on Laser-induced Damage of Fused Silica Surfaces at 355 Nm written by and published by . This book was released on 1998 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Fused silica windows were artificially contaminated to estimate the resistance of target chamber debris shields against laser damage during NIF operation. Uniform contamination thin films (1 to 5 nm thick) were prepared by sputtering various materials (Au, Al, Cu, and B4C). The loss of transmission of the samples was first measured. They were then tested at 355 nm in air with an 8-ns Nd:YAG laser. The damage morphologies were characterized by Nomarski optical microscopy and SEM. Both theory and experiments showed that metal contamination for films as thin as 1 nm leads to a substantial loss of transmission. The laser damage resistance dropped very uniformly across the entire surface (e.g. 6 J/cm2 for 5 nm of Cu). The damage morphology characterization showed that contrary to clean silica, metal coated samples did not produce pits on the surface. B4C coated silica, on the other hand, led to a higher density of such damage pits. A model for light absorption in the thin film was coupled with a simple heat deposition and diffusion model to perform preliminary theoretical estimates of damage thresholds. The estimates of the loss due to light absorption and reflection pointed out significant .differences between metals (e.g. Al and Au). The damage threshold predictions were in qualitative agreement with experimental measurements.
Book Synopsis Study of the Effects of Polishing, Etching, Cleaving, and Water Leaching on the UV Laser Damage of Fused Silica by :
Download or read book Study of the Effects of Polishing, Etching, Cleaving, and Water Leaching on the UV Laser Damage of Fused Silica written by and published by . This book was released on 1997 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt: A damage morphology study was performed with a 355 nm Nd:YAG laser on synthetic UV-grade fused silica to determine the effects of post- polish chemical etching on laser-induced damage, compare damage morphologies of cleaved and polished surfaces, and understand the effects of the hydrolyzed surface layer and waste-crack interactions. The samples were polished, then chemically etched in buffered HF solution to remove 45,90,135, and 180 nm of surface material. Another set of samples was cleaved and soaked in boiling distilled water for 1 second and 1 hour. All the samples were irradiated at damaging fluencies and characterized by Normarski optical microscopy and scanning electron microscopy. Damage was initiated as micro-pits on both input and output surfaces of the polished fused silica sample. At higher fluencies, the micro-pits generated cracks on the surface. Laser damage of the polished surface showed significant trace contamination levels within a 50 nm surface layer. Micro-pit formation also appeared after irradiating cleaved fused silica surfaces at damaging fluences. Linear damage tracks corresponding cleaving tracks were often observed on cleaved surfaces. Soaking cleaved samples in water produced wide laser damage tracks.
Book Synopsis Results of Applying a Non-evaporative Mitigation Technique to Laser-initiated Surface Damage on Fused-silica by :
Download or read book Results of Applying a Non-evaporative Mitigation Technique to Laser-initiated Surface Damage on Fused-silica written by and published by . This book was released on 2010 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt: We present results from a study to determine an acceptable CO2 laser-based non-evaporative mitigation protocol for use on surface damage sites in fused-silica optics. A promising protocol is identified and evaluated on a set of surface damage sites created under ICF-type laser conditions. Mitigation protocol acceptability criteria for damage re-initiation and growth, downstream intensification, and residual stress are discussed. In previous work, we found that a power ramp at the end of the protocol effectively minimizes the residual stress (25 MPa) left in the substrate. However, the biggest difficulty in determining an acceptable protocol was balancing between low re-initiation and problematic downstream intensification. Typical growing surface damage sites mitigated with a candidate CO2 laser-based mitigation protocol all survived 351 nm, 5 ns damage testing to fluences12.5 J/cm2. The downstream intensification arising from the mitigated sites is evaluated, and all but one of the sites has 100% passing downstream damage expectation values. We demonstrate, for the first time, a successful non-evaporative 10.6?m CO2 laser mitigation protocol applicable to fused-silica optics used on fusion-class lasers like the National Ignition Facility (NIF).
Book Synopsis The Effect of Pulse Duration on the Growth Rate of Laser-induced Damage Sites at 351 Nm on Fused Silica Surfaces by :
Download or read book The Effect of Pulse Duration on the Growth Rate of Laser-induced Damage Sites at 351 Nm on Fused Silica Surfaces written by and published by . This book was released on 2009 with total page 10 pages. Available in PDF, EPUB and Kindle. Book excerpt: Past work in the area of laser-induced damage growth has shown growth rates to be primarily dependent on the laser fluence and wavelength. More recent studies suggest that growth rate, similar to the damage initiation process, is affected by a number of additional parameters including pulse duration, pulse shape, site size, and internal structure. In this study, we focus on the effect of pulse duration on the growth rate of laser damage sites located on the exit surface of fused silica optics. Our results demonstrate, for the first time, a significant dependence of growth rate at 351 nm on pulse duration from 1 ns to 15 ns as [tau]{sup 0.3} for sites in the 50-100 [mu]m size range.
Download or read book Amṯāl Sulaimān written by and published by . This book was released on 1834 with total page 96 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Methods for Mitigating Growth of Laser-Initiated Surface Damage on Fused Silcia Optics at 351nm by :
Download or read book Methods for Mitigating Growth of Laser-Initiated Surface Damage on Fused Silcia Optics at 351nm written by and published by . This book was released on 2001 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We report a summary of the surface damage, growth mitigation effort at 351nm for polished fused silica optics. The objective was to experimentally validate selected methods that could be applied to pre-initiated or retrieved-from-service optics, to stop further damage growth. A specific goal was to obtain sufficient data and information on successful methods for fused silica optics to select a single approach for processing large aperture, fused-silica optics used in high-peak-power laser applications. This paper includes the test results and the evaluation thereof, for several mitigation methods for fused silica surfaces. The mitigation methods tested in this study are wet chemical etching, cold plasma etching, CW-CO2 laser processing, and micro-flame torch processing. We found that CW-CO2 laser processing produces the most significant and consistent results to halt laser-induced surface damage growth on fused silica. We recorded successful mitigation of the growth of laser-induced surface damage sites as large as 0.5mm diameter, for 1000 shots at 351nm and fluences in the range of 8 to 13J/cm2, (almost equal to)11ns pulse length. We obtained sufficient data for elimination of damage growth using CO2 laser processing on sub-aperture representative optics, to proceed with application to large aperture ((almost equal to)40 x 40cm2) fused silica.
Book Synopsis Laser Damage Performance of Fused Silica Optical Componets Measured on the Beamlet Laser at 35nm by :
Download or read book Laser Damage Performance of Fused Silica Optical Componets Measured on the Beamlet Laser at 35nm written by and published by . This book was released on 1998 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A statistics-based model is being developed to predict the laser-damage-limited lifetime of UV optical components on the NIF laser. In order to provide data for the model, laser damage experiments were performed on the Beamlet laser system at LLNL (aperture: 34 cm x 34 cm). Three prototype NIF focus lenses were exposed to 351 nm pulses (1.5 ns or 3 ns) during four experimental campaigns, each consisting of 23 to 38 pulses at NIF relevant fluences. Each lens was sol-gel AR coated and all laser exposures were performed in a vacuum environment. Through inspections of the lens before, during and after the campaigns, pulse-to-pulse damage growth rates were measured for damage initiating both on the surfaces and at bulk inclusions. Radial growth rates measured for rear surface damage was typically 10x higher than that measured in the bulk or at the front surface. No significant correlation of growth rate to precursor type was indicated. For 5 J/cm2, 3 ns pulses the typical radial growth rate was nominally 20 μm/pulse. Average growth rates measured on three lenses made by two manufacturers were in good agreement. While the growth rate clearly increased with fluence, the data obtained was insufficient to quantify the dependence. The growth rates reported here were 20x-50x higher than values predicted from off-line studies of bare surfaces in air.
Book Synopsis Laser-induced Damage Initiated on the Surface of Particle Contaminated Fused Silica Optics at 1064nm by : Kenneth Jerome Francis Michlitsch
Download or read book Laser-induced Damage Initiated on the Surface of Particle Contaminated Fused Silica Optics at 1064nm written by Kenneth Jerome Francis Michlitsch and published by . This book was released on 1997 with total page 92 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Growth of Laser Damage in Fused Silica by :
Download or read book Growth of Laser Damage in Fused Silica written by and published by . This book was released on 2007 with total page 11 pages. Available in PDF, EPUB and Kindle. Book excerpt: Growth of laser initiated damage plays a major role in determining optics lifetime in high power laser systems. Previous measurements have established that the lateral diameter grows exponentially. Knowledge of the growth of the site in the propagation direction is also important, especially so when considering techniques designed to mitigate damage growth, where it is required to reach all the subsurface damage. In this work, we present data on both the diameter and the depth of a growing exit surface damage sites in fused silica. Measured growth rates with both 351 nm illumination and with combined 351 nm and 1054 nm illumination are discussed.
Book Synopsis Catastrophic Failure of Contaminated Fused Silica Optics at 355 Nm by :
Download or read book Catastrophic Failure of Contaminated Fused Silica Optics at 355 Nm written by and published by . This book was released on 1996 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt: For years, contamination has been known to degrade the performance of optics and to sometimes initiate laser-induced damage to initiate. This study has W to quantify these effects for fused silica windows used at 355 mm Contamination particles (Al, Cu, TiO2 and ZrO2) were artificially deposited onto the surface and damage tests were conducted with a 3 ns NdYAG laser. The damage morphology was characterized by Nomarski optical microscopy. The results showed that the damage morphology for input and output surface contamination is different. For input surface contamination, both input and output surfaces can damage. In particular, the particle can induce pitting or drilling of the surface where the beam exits. Such damage usually grows catastrophically. Output surface contamination is usually ablated away on the shot but can also induce catastrophic damage. Plasmas are observed during illumination and seem to play an important role in the damage mechanism. The relationship between fluence and contamination size for which catastrophic damage occurred was plotted for different contamination materials. The results show that particles even as small as 10 [mu]m can substantially decrease the damage threshold of the window and that metallic particles on the input surface have a more negative effect than oxide particles.
Book Synopsis HF-based Etching Processes for Improving Laser Damage Resistance of Fused Silica Optical Surfaces by :
Download or read book HF-based Etching Processes for Improving Laser Damage Resistance of Fused Silica Optical Surfaces written by and published by . This book was released on 2010 with total page 32 pages. Available in PDF, EPUB and Kindle. Book excerpt: The effect of various HF-based etching processes on the laser damage resistance of scratched fused silica surfaces has been investigated. Conventionally polished and subsequently scratched fused silica plates were treated by submerging in various HF-based etchants (HF or NH4F:HF at various ratios and concentrations) under different process conditions (e.g., agitation frequencies, etch times, rinse conditions, and environmental cleanliness). Subsequently, the laser damage resistance (at 351 or 355 nm) of the treated surface was measured. The laser damage resistance was found to be strongly process dependent and scaled inversely with scratch width. The etching process was optimized to remove or prevent the presence of identified precursors (chemical impurities, fracture surfaces, and silica-based redeposit) known to lead to laser damage initiation. The redeposit precursor was reduced (and hence the damage threshold was increased) by: (1) increasing the SiF62− solubility through reduction in the NH4F concentration and impurity cation impurities, and (2) improving the mass transport of reaction product (SiF62−) (using high frequency ultrasonic agitation and excessive spray rinsing) away from the etched surface. A 2D finite element crack-etching and rinsing mass transport model (incorporating diffusion and advection) was used to predict reaction product concentration. The predictions are consistent with the experimentally observed process trends. The laser damage thresholds also increased with etched amount (up to ≈30 [mu]m), which has been attributed to: (1) etching through lateral cracks where there is poor acid penetration, and (2) increasing the crack opening resulting in increased mass transport rates. With the optimized etch process, laser damage resistance increased dramatically; the average threshold fluence for damage initiation for 30 [mu]m wide scratches increased from 7 to 41 J/cm2, and the statistical probability of damage initiation at 12 J/cm2 of an ensemble of scratches decreased from ≈100 mm−1 of scratch length to ≈0.001 mm−1.
