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Study Of Co2 Laser Smoothing Of Surface Roughness In Fused Silica
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Book Synopsis Study of CO2 Laser Smoothing of Surface Roughness in Fused Silica by :
Download or read book Study of CO2 Laser Smoothing of Surface Roughness in Fused Silica written by and published by . This book was released on 2009 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt: Small micrometer-sized roughness on optical surfaces, caused by laser damage and/or redeposition of laser ablated material, can cause local electric field intensification which may lead to damage initiation both on the optics and/or downstream. We examined the smoothing of etched periodic surface structures on SiO2 substrate with 10.6 [mu]m CO2 laser using atomic force microscopy. The characteristic surface tension driven mass flow of the glass under different laser parameters were simulated using computational fluid dynamics and correlated with experimental results. We found that during CO2 laser polishing the estimate viscosity of the silica glass appears to be higher than typical literature values measured at a temperature similar to the laser heating conditions. This discrepancy can be explained by the observation that at high temperature, a significant portion of the hydroxyl content in the layer of heated silica glass can diffuse out resulting in a much stiffer glass.
Book Synopsis CO2-laser Polishing of Fused Silica Surfaces for Increased Laser Damage Resistance at 1. 06. Mu. M by :
Download or read book CO2-laser Polishing of Fused Silica Surfaces for Increased Laser Damage Resistance at 1. 06. Mu. M written by and published by . This book was released on 1980 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Bare fused silica surfaces were prepared by subjecting the mechanically polished surface to a rastered cw CO2 laser beam. Analysis shows that this processing causes: (a) removal of a uniform layer of fused silica; and (b) a probable re-fusing or healing of existing subsurface fractures. The fused silica removal rate is found to be a function of the laser intensity and scan rate. These surfaces are seen to have very low scatter and to be very smooth. In addition, they have exhibited entrance surface damage thresholds at 1.06 .mu.m, and 1 nsec, which are substantially above those seen on the mechanically polished surface. When damage does occur, it tends to be at a few isolated points rather than the general uniform damage seen on the mechanicaly polished part. In addition to the damage results, we will discuss an observational technique used for viewing these surfaces which employs dark-field illumination.
Book Synopsis Effect of Surface Roughness on CO2 Laser Absorption by 316L Stainless Steel and Aluminum by : M. Ahmed Obeidi
Download or read book Effect of Surface Roughness on CO2 Laser Absorption by 316L Stainless Steel and Aluminum written by M. Ahmed Obeidi and published by . This book was released on 2018 with total page 11 pages. Available in PDF, EPUB and Kindle. Book excerpt: The roughness of a materials surface is a significant factor affecting the absorption of energy when scanned with laser beam radiation. It is a robust variable affecting the entire laser process cost and the appropriate levels for the laser processing parameters, such as the power applied. It is thus an important factor for many processes, such as laser cutting, welding, roughening, and polishing. As such, an examination of the effect of roughness on laser absorption is desirable to determine how input parameters, such as power, must be adjusted when working with different roughness and the potential power savings of roughening samples, or eliminating polishing or finishing steps, before laser processing. In this study, a comparison of the effect of the surface roughness of flat 316L stainless steel and aluminum samples on the thermal energy absorbed in laser processing was investigated. The aim was to characterize the effect and identify the potential energy savings. Samples were processed as received and either polished or roughened, such that there were five different roughness levels for each material. Individual carbon dioxide laser shots were applied with large unprocessed gaps in order to allow clear investigation of the crater depth dimensions. The width, length, and depth of the craters were measured by both scanning electron microscope and three-dimensional microscope, with larger dimensions indicating a greater absorption of the laser energy. The expected outcome of the study was confirmed, finding a noticeable improvement in the absorbed energy on the rougher surfaces for both materials, with a saving of ~62 % in the laser power applied when the aluminum surface roughness increased from 2.4 ?m to 7.03 ?m.
Book Synopsis CO2-Laser Polishing for Reduction of 351-nm Surface Damage Initiation in Fused Silica by :
Download or read book CO2-Laser Polishing for Reduction of 351-nm Surface Damage Initiation in Fused Silica written by and published by . This book was released on 2001 with total page 9 pages. Available in PDF, EPUB and Kindle. Book excerpt: We have applied a carbon dioxide (CO2) raster scanning laser polishing technique on two types of fused silica flat optics to determine the efficacy of CO2-laser polishing as a method to increase the 351-nm laser damage resistance of optic surfaces. R-on-1 damage test results show that the fluence for any given 355-nm damage probability is 10-15 J/cm2 higher (at 3 ns pulse length, scaled) for the CO2-laser polished samples. Poor quality and good quality surfaces respond to the treatment such that their surface damage resistance is brought to approximately the same level. Surface stress and the resultant effect on wavefront quality remain key technology issues that would need to be addressed for a robust deployment.
Book Synopsis Proceedings of the 3rd Annual International Conference on Material, Machines and Methods for Sustainable Development (MMMS2022) by : Banh Tien Long
Download or read book Proceedings of the 3rd Annual International Conference on Material, Machines and Methods for Sustainable Development (MMMS2022) written by Banh Tien Long and published by Springer Nature. This book was released on with total page 583 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book NBS Special Publication written by and published by . This book was released on 1968 with total page 684 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis 1.06 ?m Laser-Induced Breakdown of CO2-Laser-Polished Fused SiO2 by : PA. Temple
Download or read book 1.06 ?m Laser-Induced Breakdown of CO2-Laser-Polished Fused SiO2 written by PA. Temple and published by . This book was released on 1981 with total page 10 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fused silica surfaces have been treated with continuous wave CO2-laser radiation in an improved raster technique. Laser damage data for 1.06-?m, 9-nsec, small-spot irradiation are presented. It is shown that a reasonably sharp transition from laser damage prone to laser damage resistant surfaces takes place over a small CO2-laser power range. The transition to high damage resistance takes place at a silica surface temperature where material flow begins to take place, as evidenced by the onset of residual strain in the CO2-processed part. These data are taken as evidence that microcrack healing is an important mechanism in increased damage resistance in CO2-polished parts. Also presented are data which show that CO2-treated surfaces have a small-spot damage threshold at least as high as the bulk damage threshold of SiO2. In addition, these treated parts show no obvious change in surface appearance, as seen in total internal reflection microscopy. They also show little change in transmissive figure. It is suggested that uniform preheating be used to eliminate the strain presently seen in CO2-treated parts.
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 1982 with total page 520 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Publications of the National Institute of Standards and Technology ... Catalog by : National Institute of Standards and Technology (U.S.)
Download or read book Publications of the National Institute of Standards and Technology ... Catalog written by National Institute of Standards and Technology (U.S.) and published by . This book was released on 1981 with total page 680 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Publications by : United States. National Bureau of Standards
Download or read book Publications written by United States. National Bureau of Standards and published by . This book was released on 1981 with total page 684 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Mechanisms of CO2 Laser Mitigation of Laser Damage Growth in Fused Silica by :
Download or read book Mechanisms of CO2 Laser Mitigation of Laser Damage Growth in Fused Silica written by and published by . This book was released on 2002 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Theoretical models for heating, evaporation, material flow, and stress and strain generation accompanying CO2 laser damage mitigation and surface treatment of fused silica are developed to aid understanding of scaling with process parameters. We find that lateral nonlinear heat transport is an important cooling mechanism, more significant than evaporative cooling. Scaling laws relating experiments with different set of parameters are presented. Transverse conduction, together with the increased thermal conductivity at high temperatures, allows a gentle evaporation regime at low laser intensity in which the rate can be controlled via laser fluence. For higher laser intensity, recoil momentum imparted by rapid evaporation generates pressure, which can lead to transverse flow of the melted material. Only a very thin layer can flow because viscosity increases rapidly with depth. Evaporation and flow are subject to instabilities that can impact surface quality, especially surface flatness, if large areas are processed. Also material flow can heal cracks and improve material quality. Analysis of stress indicates that maximal tensile stresses of order 0.1 GPa, comparable to the tensile strength, can be generated.
Book Synopsis The Effect of Assist Gas on the Surface Roughness for Carbon Dioxide Laser Cutting Process by : Muhammad Zaid Mohamad Mohtar
Download or read book The Effect of Assist Gas on the Surface Roughness for Carbon Dioxide Laser Cutting Process written by Muhammad Zaid Mohamad Mohtar and published by . This book was released on 2012 with total page 57 pages. Available in PDF, EPUB and Kindle. Book excerpt: This study focuses on the effect of assist gases on the surface roughness for Carbon Dioxide (CO2) laser cutting process. The analysis of the surface roughness has been determined by Surfcom 130A surface roughness tester which it place in laboratory. The material used for this experiment is acrylic sheet with 2.5 mm thickness. In this process the cut quality is very important. The parameters in laser cutting are cutting speed, keft width, laser power, chemistry of gas, nozzle exit parameter, nozzle design, thickness of the specimen and surface quality. In oxygen assist laser cutting, the gas plays two roles, one is to generated additional thermal energy during penetration and second role is to supply the shear force to the gas boundary to eject the molten metal formed during the cutting process. However, for this study, two parameters are selected. There are type of assist gas and gas pressure. Finally, the result show that the no assist gas with the lower pressure bars at certain speed is better quality on surface roughness cutting.
Book Synopsis Laser Induced Damage in Optical Materials, 1982 by :
Download or read book Laser Induced Damage in Optical Materials, 1982 written by and published by . This book was released on 1984 with total page 508 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Residual Stress and Damage-induced Critical Fracture on CO2 Laser Treated Fused Silica by :
Download or read book Residual Stress and Damage-induced Critical Fracture on CO2 Laser Treated Fused Silica written by and published by . This book was released on 2009 with total page 13 pages. Available in PDF, EPUB and Kindle. Book excerpt: Localized damage repair and polishing of silica-based optics using mid- and far-IR CO2 lasers has been shown to be an effective method for increasing optical damage threshold in the UV. However, it is known that CO2 laser heating of silicate surfaces can lead to a level of residual stress capable of causing critical fracture either during or after laser treatment. Sufficient control of the surface temperature as a function of time and position is therefore required to limit this residual stress to an acceptable level to avoid critical fracture. In this work they present the results of 351 nm, 3 ns Gaussian damage growth experiments within regions of varying residual stress caused by prior CO2 laser exposures. Thermally stressed regions were non-destructively characterized using polarimetry and confocal Raman microscopy to measure the stress induced birefringence and fictive temperature respectively. For 1 ≈ 40s square pulse CO2 laser exposures created over 0.5-1.25 kW/cm2 with a 1-3 mm 1/e2 diameter beam (T{sub max} ≈ 1500-3000 K), the critical damage site size leading to fracture increases weakly with peak temperature, but shows a stronger dependence on cooling rate, as predicted by finite element hydrodynamics simulations. Confocal micro-Raman was used to probe structural changes to the glass over different thermal histories and indicated a maximum fictive temperature of 1900K for T{sub max} ≥ 2000 K. The effect of cooling rate on fictive temperature caused by CO2 laser heating are consistent with finite element calculations based on a Tool-Narayanaswamy relaxation model.
Book Synopsis Laser Program Annual Report, 1979 by :
Download or read book Laser Program Annual Report, 1979 written by and published by . This book was released on 1980 with total page 300 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Influence of Secondary Treatment with CO2 Laser Irradiation for Mitigation Site on Fused Silica Surface*Project Supported by the National Natural Science Foundation of China (Grant Nos. 61505170, 61505171, and 51535003), the Joint Fund of the National Natural Science Foundation of China, the Chinese Academy of Engineering Physics (Grant No. U1530109), and the China Postdoctoral Science Foundation (Grant No. 2016M592709). by :
Download or read book Influence of Secondary Treatment with CO2 Laser Irradiation for Mitigation Site on Fused Silica Surface*Project Supported by the National Natural Science Foundation of China (Grant Nos. 61505170, 61505171, and 51535003), the Joint Fund of the National Natural Science Foundation of China, the Chinese Academy of Engineering Physics (Grant No. U1530109), and the China Postdoctoral Science Foundation (Grant No. 2016M592709). written by and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: The ablation debris and raised rim, as well as residual stress and deep crater will be formed during the mitigation of damage site with a CO2 laser irradiation on fused silica surface, which greatly affects the laser damage resistance of optics. In this study, the experimental study combined with numerical simulation is utilized to investigate the effect of the secondary treatment on a mitigated site by CO2 laser irradiation. The results indicate that the ablation debris and the raised rim can be completely eliminated and the depth of crater can be reduced. Notable results show that the residual stress of the mitigation site after treatment will reduce two-thirds of the original stress. Finally, the elimination and the controlling mechanism of secondary treatment on the debris and raised rim, as well as the reasons for changing the profile and stress are analyzed. The results can provide a reference for the optimization treatment of mitigation sites by CO2 laser secondary treatment.
Book Synopsis Thermal Transport in CO2 Laser Irradiated Fused Silica by :
Download or read book Thermal Transport in CO2 Laser Irradiated Fused Silica written by and published by . This book was released on 2009 with total page 17 pages. Available in PDF, EPUB and Kindle. Book excerpt: In situ spatial and temporal temperature measurements of pristine fused silica surfaces heated with a 10.6 [mu]m CO2 laser were obtained using an infrared radiation thermometer based on a Mercury Cadmium Telluride (MCT) camera. Laser spot sizes ranged from 250 [mu]m to 1000 [mu]m diameter with peak axial irradiance levels of 0.13 to 16 kW/cm2. For temperatures below 2800K, the measured steady-state surface temperature is observed to rise linearly with both increasing beam size and incident laser irradiance. The effective thermal conductivity estimated over this range was approximately 2W/mK, in good agreement with classical calculations based on phonon heat capacities. Similarly, time-dependent temperature measurements up to 2000K yielded thermal diffusivity values which were close to reported values of 7 x 10−7 m2/s. Above ≈2800K, the fused silica surface temperature asymptotically approaches 3100K as laser power is further increased, consistent with the onset of evaporative heat losses near the silica boiling point. These results show that in the laser heating regime studied here, the T3 temperature dependent thermal conductivity due to radiation transport can be neglected, but at temperatures above 2800K heat transport due to evaporation must be considered. The thermal transport in fused silica up to 2800K, over a range of conditions, can then be adequately described by a linear diffusive heat equation assuming constant thermal properties.
