R-on-1 automatic mapping: a new tool for laser damage testing

Hue, Jean; Garrec, Pierre; Dijon, Jean; Lyan, Philippe

doi:10.1117/12.240352

Cited by 25 publications

(13 citation statements)

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“…The small beam testing allowed for testing the laser damage threshold of a single crack at a time by ramping up the fluence until damage was observed [18]. A Q-switched Nd:YAG laser (Coherent Infinity) was used to provide 355 nm laser light (3ns pulse, temporal and spatial profile Gaussian, beam waist 1/e 2 diameter 80 m).…”

Section: Laser Damage Testingmentioning

confidence: 99%

HF‐Based Etching Processes for Improving Laser Damage Resistance of Fused Silica Optical Surfaces

Suratwala

Miller

Bude

et al. 2010

Journal of the American Ceramic Society

218

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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 μm), 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 μm 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.

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Section: Laser Damage Testingmentioning

confidence: 99%

HF‐Based Etching Processes for Improving Laser Damage Resistance of Fused Silica Optical Surfaces

Suratwala

Miller

Bude

et al. 2010

Journal of the American Ceramic Society

218

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“…[19] For optics with randomly distributed damage precursors, damage testing is typically performed using a centimeter-sized beam and reported as damage density as a function of laser fluence (). The test results using small beams, on the other hand, may depend strongly on the beam size.…”

Section: Methodsmentioning

confidence: 99%

Thermal annealing of laser damage precursors on fused silica surfaces

et al. 2012

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Previous studies have identified two significant precursors of laser damage on fused silica surfaces at fluenes below ~35J/cm 2 , photoactive impurities in the polishing layer and surface fractures. In the present work, isothermal heating is studied as a means of remediating the highly absorptive, defect structure associated with surface fractures. A series of Vickers indentations were applied to silica surfaces at loads between 0.5N and 10N creating fracture networks between ~10m and ~50m in diameter. The indentations were characterized prior to and following thermal annealing under various time and temperature conditions using confocal timeresolved photo-luminescence (CTP) imaging, and R/1 optical damage testing with 3ns, 355nm laser pulses. Significant improvements in the damage thresholds, together with corresponding reductions in CTP intensity, were observed at temperatures well below the glass transition temperature (T g ). For example, the damage threshold on 05.N indentations which typically initiates at fluences <8 J/cm 2, could be improved >35 J/cm 2 through the use of a ~750 °C thermal treatment. Larger fracture networks required longer or higher temperature treatment to achieve similar results. At an annealing temperature >1100°C, optical microscopy indicates morphological changes in some of the fracture structure of indentations, although remnants of the original fracture and significant deformation was still observed after thermal annealing. This study demonstrates the potential of using isothermal annealing as a means of improving the laser damage resistance of fused silica optical components. Similarly, it provides a means of further understanding the physics associated with optical damage and related mitigation processes.

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“…The progress made in electronic devices and software is also a great help to build such automatic systems with more capabilities and with a friendly use. It allows to have more data in a less time with a better degree ofconfidence 6,7 With automatic facilities, the study ofnew field can be investigated. For instance, there is a request to be able to certify optics up to almost 0.25 m2 for laser programs as Megajoule, National Ignition Facility4'8, .…”

Section: Introductionmentioning

confidence: 99%

Automatic YAG damage test benches: additional possibilities

Hue¹,

Dijon²,

Ravel³

et al. 1999

SPIE Proceedings

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The automatic damage test benches allow to obtain more data in less time but also to imagine new laser damage tests. Thereby, new questions can be asked and more answers can be provided. In this paper, the 3 YAG automatic damage test facilities build up at the laboratory will be shown. There are based on well-known principles : an half wave plate to adjust the wished peak fluence and a scattered light measurement in real time to detect the damage appearances. Many tests are developed around these benches as the usual hon-i, N-on-i, R-on-1, S-on-i tests and raster scans previously proposed by other laboratories. On all our test benches, these standard tests are driven by the same software designed at the laboratory : "Wintfl". But new tests and characterizations are also added. Indeed, on these thcilities the aging ofthe optics at various repetition rate under constant fluence (like S-on-i with or without a limit number of shots) are carried out. An automatic defect count has been also implemented. This tool is able to evaluate the number of defects after cleaning or after coating but also between laser irradiation. New tests are also imagined. The so-called HR-on-i test (High Ramp), which is a R-on4 (Ramp) test without beginning at zero has been achieved. It allows to compare 1-on-I and R-on-1 distributions performed with exactly the same damage criterion. Other parameters can be investigated as the speed of the motor ramp during the R-on-1 test, the pulse repetition frequency during the S-on-i test,... In this article, after a short presentation of our test bench facilities, the convenient possibilities of automatic YAG test benches are illustrated with experimental results.

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R-on-1 automatic mapping: a new tool for laser damage testing

Cited by 25 publications

References 0 publications

HF‐Based Etching Processes for Improving Laser Damage Resistance of Fused Silica Optical Surfaces

HF‐Based Etching Processes for Improving Laser Damage Resistance of Fused Silica Optical Surfaces

Thermal annealing of laser damage precursors on fused silica surfaces

Automatic YAG damage test benches: additional possibilities

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