Detection and measurement of subsurface damage ground optical surfaces are major concern in the assessment high thresholds fused silica optics for power laser applications.We herein detail a new principle SSD based on utilization HF acid etching.We also review compare different (SSD) characterization techniques applied to fine samples.We demonstrate good concordance between measurements.

We report an experimental investigation of fluorescence confocal microscopy as a tool to measure subsurface damage on grinded fused silica optics.Confocal was performed with excitation at the wavelength 405 nm fixed abrasive diamond samples.We detail measured spectrums and compare them those oil based coolants grinding slurries.We evidence that coolant used in induces marks damages eases its observation.Such residual traces might also be involved laser process.

A self-consistent approach is proposed to determine the temperature dependent thermal conductivity k(T) of fused silica, for a range temperatures up material evaporation using CO2 laser irradiation. Calculation silica two-dimensional axi-symmetric code was linked step by as power increased with experimental measurements infrared thermography. We show that previously reported does not reproduce temporal profile well our adaptive fit which shows evolves slope discontinuities at annealing and...

CO2 laser heating of silica glass is used in many scientific and industrial applications. Particularly, localized has demonstrated its ability to mitigate surface damage on optics for high power To develop such applications, the control temperature, heat affected area, resulting mechanical stresses are critical. Therefore, it necessary understand transformation, material ejection, thermo-mechanical induced by subsequent cooling. In this paper, we detail development comprehensive numerical...

Laser damage mitigation' is a process developed to prevent the growth of nanosecond laser-initiated sites under successive irradiation. It consists re-fusing area with CO2 laser. In this paper we investigate stress field created around mitigated which could have an influence on efficiency process. A numerical model laser interaction fused silica developed. takes into account energy absorption, heat transfer, thermally induced and birefringence. Residual near in samples characterized specific...

We investigate the capacity of magnetorheological finishing (MRF) process to remove surface and subsurface defects fused silica optics. Polished samples with engineered were manufactured characterized. Uniform material removals performed a QED Q22-XE machine using different MRF parameters in order these defects. provide evidence that whatever are, is able Moreover, we show induces pollution glass interface similar conventional polishing processes.

We investigate the interest of deep wet etching with HF/HNO3 or KOH solutions as a final step after polishing to improve fused silica optics laser damage resistance at wavelength 351 nm. This comparison is carried out on scratches engineered high threshold polished optics. evidence that both and are efficient passivate thus their up level surface. The effect these etchings surface roughness aspect also studied. show solution exhibit better overall quality in tested conditions. Given safety...

In situ spatial and temporal temperature measurements of a fused silica surface heated by 10.6 μm CO2 laser were performed using an infrared camera. These derived from heat flux emission the silica. High measurements—in range 400–2500 K—were at semi-transparent media with high resolution. Particular attention was given to experimental conception calibration device. Moreover, both conventional interferential microscopes used characterize surfaces after irradiation. By associating these...

In this work, CO2 laser pulses with a wavelength of 10.6 μm, beam diameter about 400 and an intensity the order 190 kW/cm2 are used to produce microablations on fused silica samples pulse fluences ranging from ablation threshold up 38 J/cm2. We obtain pits average depths few nanometers tens micrometers study their morphology evolution as function width pulse-repetition frequency. Our experimental results improve 2D axisymmetric finite-element model that analyzes heat transfer process in...

We investigate the efficiency of local CO₂laser processing scratches on silica optics in order to enhance nanosecond UV-laser damage resistance. The surface deformations induced by process have been measured for different parameters and then pulse duration beam diameter chosen accordingly limit those below 1 µm. From study laser resistance as a function material modifications we identify range optimal radiation allowing complete elimination associated with high threshold damage. Calculation...

We report on the development of a mitigation process to prevent growth UV nanosecond laser-initiated damage sites under successive irradiations fused silica components. The developed is based fast microablation as it has been proposed by Bass et al. [Bass al., Proc. SPIE 7842, 784220 (2010)]. This accomplished displacement CO2 laser spot with galvanometer beam scanner form crater typical conical shape mitigate large (millimetric) and deep (few hundred microns) sites. present experimental...

In this work, the polishing‐induced contamination layer at fused silica optics surface was studied with various interface analysis techniques: Secondary Ion Mass Spectroscopy ( SIMS ), Electron Probe Microanalysis EPMA X‐Ray Photoelectron XPS and Inductively Coupled Plasma—Optical Emission ICP ‐ OES ). Samples were prepared using an MRF polishing machine cerium‐based slurry. The cerium iron penetration concentration measured in out of defects. Cerium is embedded a 60 nm concentrated 1200...

Loose abrasive lapping is widely used to prepare optical glass before its final polishing. We carried out a comparison of 20 different slurries from four vendors. Slurry particle sizes and morphologies were measured. Fused silica samples lapped with these on single side polishing machine characterized in terms surface roughness depth subsurface damage (SSD). Effects load, rotation speed, slurry concentration during roughness, material removal rate, SSD investigated.

CO(2) laser is an interesting tool to repair defects on silica optics. We studied UV nanosecond laser-induced damage in fused after heating. The localization of sites and the threshold are closely related stress area induced by By applying a suitable second heating, we managed eliminate debris issued from redeposited modify area. As consequence, significant increase resistance has been observed. This process offers possibility improve repairing sufficiently extend lifetime components.

Significant improvement in the polishing process of fused silica optical components has increased their lifetimes at 351 nm. Nevertheless, for large laser facilities like LaserMegaJoule (LMJ), zero defect are not yet available. Therefore, a damage mitigation technique been developed to prevent growth laser-initiated sites. Because difficulty produce mitigated sites with sufficiently depth, initial morphology mitigate is critical issue. The aim this work determine parameters (pulse duration,...

Scratches at the surface of fused silica optics can be detrimental for performance optical systems. A carbon dioxide (CO 2 ) laser is an interesting tool to remove those scratches because it melt efficiently in a rapid and localized way, without generating debris. In this article, we propose new process fabrication, which uses CO between polishing finishing steps. This linear with no iterative operations scratch removal. applied on optic representative megajoule facility production. Indeed,...

We investigate the effect of different heat treatments on laser-induced damage probabilities fused silica samples. Isothermal annealing in a furnace is applied, with temperatures range 700–1100 °C and 12 h time, to super-polished The surface flatness laser at 3 ns, 351 nm are measured before after procedures. have found significant improvement initial 1050 for h. A similar study has been conducted CO2 laser-processed sites Before annealing, we studied morphology sites, evolution residual...

A technique that provides quantitative and spatially resolved retardance measurement is studied for application to laser-induced modification in transparent materials. The method based on the of optical path differences between two wavefronts carrying different polarizations, measured by a wavefront sensor placed image plane microscope. We have applied investigation stress distribution induced CO2 laser processing fused silica samples. By comparing experiments results thermomechanical...

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Fused silica optics often exhibit surface scratches after polishing that radically reduce their damage resistance at the wavelength of 351 nm in nanosecond regime. Consequently, chemical treatments are used to increase threshold and ensure a safe operation these large fusion-scale laser facilities. Here, we investigate reasons for such an improvement. We study effect HF-based wet etching on scratch morphology propose simple analytic model reflect widening during etching. also use finite...

During the development of laser megajoule (LMJ), a high power facility dedicated to DT fusion, CEA has made important efforts understand and improve induced damage threshold fused silica optics at wavelength 351 nm. For several years, with various industrials academics partners, we have focused on optimizing grinding, lapping polishing processes increase materials performance. In this paper, describe our in fields: subsurface characterization, process simulation, diamond grinding machine...

In the context of high power laser systems, damage resistance fused silica surfaces at 351 nm in nanosecond regime is a major concern. Under successive irradiations, an initiated can grow which make component unsuitable. The localized CO₂ processing has demonstrated its ability to mitigate (stopping) growth. order large sites (millimetric), method based on fast microablation been proposed by Bass et al. [Bass al., Proc. SPIE 7842, 784220 (2010)]. This accomplished scanning spot...