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Laurent Lamaignère - One of the best experts on this subject based on the ideXlab platform.
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investigation of mechanisms leading to laser Damage Morphology
Laser-Induced Damage in Optical Materials 2016, 2016Co-Authors: Laurent Lamaignère, Maxime Chambonneau, P. Grua, Jean-yves Natoli, R Diaz, Roger Courchinoux, Jean-luc RullierAbstract:The original Damage ring pattern at the exit surface of fused silica induced by highly modulated nanosecond infrared laser pulses demonstrates the time dependence of Damage Morphology. Such a Damage structure is used to study the dynamics of the plasma issued from open cracks. This pattern originates from electron avalanche in this plasma, which simultaneously leads to an ionization front displacement in air and a silica ablation process. Experiments have shown that the propagation speed of the detonation wave reaches about 20 km/s and scales as the cube root of the laser intensity, in good agreement with theoretical hydrodynamics modeling. During this presentation, we present the different phases and the associated mechanisms leading to this peculiar Morphology: • During an incubation phase, a precursor defect provides energy deposit that drives the near surface material into a plasma state. • Next the silica plasma provides free electrons in the surrounding air, under laser irradiation an electron avalanche is initiated and generates a breakdown wave. • Then this breakdown wave leads to an expansion of the air plasma. This latter is able to heat strongly the silica surface as well as generate free electrons in its conduction band. Hence, the silica becomes activated along the breakdown wave. • When the silica has become absorbent, an ablation mechanism of silica occurs, simultaneously with the air plasma expansion, resulting in the formation of the ring patterns in the case of these modulated laser pulses. These mechanisms are supported by experiments realized in vacuum environment. A model describing the expansion of the heated area by thermal conduction due to plasma free electrons is then presented. Next, the paper deals with the two Damage formation phases that are distinguished. The first phase corresponds to the incubation of the laser flux by a subsurface defect until the Damage occurrence: an incubation fluence corresponds to this phase. The second is related to the Damage expansion that only refers to the energy deposit feeding the activation mechanism up to the end of the pulse: an expansion fluence corresponds to this phase. A striking feature is that the Damage diameters are proportional to the fluence of expansion at a given shot fluence. Indirectly, the fluences of incubation by the precursors are then determined.
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Influence of vacuum on nanosecond laser-induced surface Damage Morphology in fused silica at 1064 nm
Applied Surface Science, 2016Co-Authors: R Diaz, Maxime Chambonneau, P. Grua, Jean-yves Natoli, Jean-luc Rullier, Laurent LamaignèreAbstract:Abstract The influence of vacuum on nanosecond laser-induced Damage at the exit surface of fused silica components is investigated at 1064 nm. In the present study, as previously observed in air, ring patterns surrounding laser-induced Damage sites are systematically observed on a plane surface when initiated by multiple longitudinal modes laser pulses. Compared to air, the printed pattern is clearly more concentrated. The obtained correlation between the Damage Morphology and the temporal structure of the pulses suggests a laser-driven ablation mechanism resulting in a thorough imprint of energy deposit. The ablation process is assumed to be subsequent to an activation of the surface by hot electrons related to the diffusive expansion of a plasma formed from silica. This interpretation is strongly reinforced with additional experiments performed on an optical grating in vacuum on which Damage sites do not show any ring pattern. Qualitatively, in vacuum, the intensity-dependent ring appearance speed V ∝ I1/2 is shown to be different than in air where V ∝ I1/3. This demonstrates that the mechanisms of formation of ring patterns are different in vacuum than in air. Moreover, the mechanism responsible of the propagation of the activation front in vacuum is shown to be outdone when experiments are performed in air.
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multi wavelength study of nanosecond laser induced bulk Damage Morphology in kdp crystals
Applied Physics A, 2015Co-Authors: Stephane Reyne, Jean-yves Natoli, G Duchateau, Laurent Hallo, Laurent LamaignèreAbstract:This study reports on experimental results on the Morphology of laser-induced Damage in the bulk of potassium dihydrogen phosphate (or KDP) crystals by nanosecond pulses. The resulting Morphology of bulk laser Damage is structured in four different zones whose characteristics depend on laser parameters such as wavelength, laser polarization, and fluence. To have a better understanding of bulk formation and structure of KDP laser Damage, accessing the mechanical properties of KDP is a promising way which departs from a thermal approach which is mainly used in various models well documented in the literature. In that way, we have revisited various mechanical models of fracturation frequently used to evaluate the toughness of optical materials. Our experiments are compared to these models where the toughness is the criterion, which has been chosen to validate the modeling part of this study. We conclude that experiments are in agreement with the common values obtained by indentations tests proposed in the literature, allowing us further developments with one of these models to describe the Damage formation in KDP crystals. Also, it appears that laser Damage events split into two separated groups depending on the wavelength, with on one side 351-nm Damage sites and on the other side 1064- and 532-nm Damage sites. That suggests the existence of different physical mechanisms responsible for bulk Damage initiation in KDP crystals with respect to the wavelength.
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Laser-induced Damage Morphology in fused silica at 1064 nm in the nanosecond regime
Laser-Induced Damage in Optical Materials: 2014, 2014Co-Authors: Maxime Chambonneau, Romain Diaz, Guillaume Duchateau, P. Grua, Jean-yves Natoli, Jean-luc Rullier, Laurent LamaignèreAbstract:ABSTRACT The Morphology of laser-induced Damage sites at the exit surface of fused silica is tightly correlated to the mode composition of the nanosecond laser pulses at 1064 nm. In the single longitudinal mode (SLM) configuration, a molten and fractured central zone is surrounded by a funnel-shaped surface modification. Ring patterns surround the Damage sites when these are initiated by multiple longitudinal modes (MLM) laser pulses. In this last mode configuration, the pulses temporal profiles as well as the Damage ring patterns differ from pulse to pulse. The appearance chronology of the rings is found to be closely related to the temporal shape of the laser pulses. This supports that the Damage Morphology originates from the coupling of a laser-supported detonation wave propagating in air with an ablation mechanism in silica. In our experiments, the propagation speed of the detonation wave reaches about 20 km/s and scales as the cube root of the laser intensity, in good agreement with theory. Keywords: silica, laser, Damage, Morphology, 1064 nm, plasma, ring-pattern, multiple longitudinal modes
Enam Chowdhury - One of the best experts on this subject based on the ideXlab platform.
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few cycle pulse laser induced Damage threshold determination of ultra broadband optics
Optics Express, 2016Co-Authors: Kyle Kafka, Noah Talisa, G Tempea, Drake R Austin, Catalin C Neacsu, Enam ChowdhuryAbstract:A systematic study of few-cycle pulse laser induced Damage threshold (LIDT) determination was performed for commercially-available ultra-broadband optics, (i.e. chirped mirrors, silver mirrors, beamsplitters, etc.) in vacuum and in air, for single and multi-pulse regime (S-on-1). Multi-pulse Damage Morphology at fluences below the single-pulse LIDT was studied in order to investigate the mechanisms leading to the onset of Damage. Stark morphological contrast was observed between multi-pulse Damage sites formed in air versus those in vacuum. One effect of vacuum testing compared to air included suppression of laser-induced periodic surface structures (LIPSS) formation, possibly influenced by a reduced presence of Damage debris. Another effect of vacuum was occasional lowering of LIDT, which appears to be due to the stress-strain performance of the coating design during laser irradiation and under the external stress of vacuum ambience. A fused silica substrate is also examined, and a non-LIPSS nanostructuring is observed on the surface. Possible mechanisms are discussed.
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few cycle pulse laser induced Damage of thin films in air and vacuum ambience
Laser-Induced Damage in Optical Materials 2016, 2016Co-Authors: Kyle Kafka, Noah Talisa, G Tempea, Drake R Austin, Catalin C Neacsu, Enam ChowdhuryAbstract:Laser-induced Damage mechanisms were investigated for an ultra-broadband chirped mirror, as part of a systematic study of few-cycle pulse laser-induced Damage threshold (LIDT) of widely-used ultra-broadband optics, in vacuum and in air, for single and multi-pulse regimes (S-on-1). Microscopic analysis of Damage Morphology suggests that three different Damage mechanisms occur across the fluence range 0.15-0.4J/cm2, while no ablation was yet observed. The three regimes resulted in shallow swelling (< 10 nm tall), tall blistering (~ 150 nm tall), and annular blistering (Damage suppressed at highest intensity, forming a ring shape). Descriptions of the potential mechanisms are discussed.
Jianda Shao - One of the best experts on this subject based on the ideXlab platform.
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influence of deposition temperature and precursor pulse time on properties of sio2 hfo2 monolayers deposited by peald
Tenth International Conference on Thin Film Physics and Applications (TFPA 2019), 2019Co-Authors: Chaoyi Yin, Yuanan Zhao, Meiping Zhu, Chen Song, Tingting Zeng, Yanzhi Wang, Jianda ShaoAbstract:Plasma-enhanced atomic layer deposition (PEALD) has been widely used in microelectronics due to its precise coating thickness control and high uniformity. Coating qualities are strongly affected by deposition parameters and can be tailored accordingly. In this work, SiO2 and HfO2 monolayers were deposited by PEALD on fused silica and BK7 substrates for different measurement. The influence of deposition temperature and precursor pulse time on both coatings were studied. Coating thickness was obtained by ellipsometer and coating roughness was extracted by atomic force microscope. Laser-induced Damage threshold (LIDT) and Damage Morphology were also studied. By optimizing the process parameters, coatings with desired properties can be deposited.
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influence of sio2 overcoat layer and electric field distribution on laser Damage threshold and Damage Morphology of transport mirror coatings
Optics Communications, 2014Co-Authors: Meiping Zhu, Xiaofeng Liu, Jianda ShaoAbstract:Abstract Four mirror coatings were designed for transporting 1064 nm light, and prepared under the same process parameters. The laser induced Damage threshold (LIDT), electric field distribution, as well as the Damage Morphology of the prepared transport mirror coating was investigated. The results indicate that the SiO2 overcoat layer and electric field distribution have a great impact on the LIDT and Damage Morphology of the transport mirror coating. A thicker SiO2 overcoat layer can suppress the delamination Damage Morphology, and significantly increase the LIDT. For the designs with similar SiO2 overcoat layer thickness, the nano-absorbing defects can survive at higher laser fluence in the design with lower electric field intensity. In addition, the HfO2 over SiO2 interface has a better interfacial strength and less “invisible” nano-absorbing defects than the SiO2 over HfO2 interface, suggesting that improving the SiO2 over HfO2 interfacial quality will be an effective way to enhance the laser Damage performance of the transport mirror coating.
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3d Morphology of laser induced bulk Damage at 355 and 1064nm in kdp crystal with different orientations
Laser Damage Symposium XLII: Annual Symposium on Optical Materials for High Power Lasers, 2010Co-Authors: Yuanan Zhao, Jianda Shao, Zhengxiu FanAbstract:In this study, wet etch process was applied to expose the bulk Damage sites in the Z-cut and X-cut KDP crystals to the surface, which gave us the direct access to the modified material for scanning electron microscopy (SEM) and optical microscopy. It's found that the Morphology of Damage site initiated with 1064nm laser was consisted of three distinct regions: a core, some oriented cracks spreading from the core, and a region of modified material surrounding the core. The 3D pattern of the crack was constructed from three distinct 2D projections, which were perpendicular to each other. The 355nm laser Damage Morphology was also investigated, and the wavelength dependence of laser Damage Morphology was presented. A simple model was proposed to explain the Damage Morphology, and the relation between the 3D crack patterns and crystal structure was discussed.
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studies of laser Damage Morphology reveal subsurface feature in fused silica
Surface and Interface Analysis, 2010Co-Authors: Yuanan Zhao, Jianda Shao, Qiling Xiao, Zhengxiu FanAbstract:We present a detailed study of the Morphology of 355 nm (6 ns) laser-induced Damage in fused silica polished by CeO2 solution. We see two distinct Damage morphologies: the gray haze and the crater. The gray haze, consisting of a high density of pin-points, appears at the fluence higher than ∼10 J/cm2, and the crater forms at ∼≥ 22 J/cm2. The size and depth of the pin-points are much smaller than the crater. The difference in the two morphologies is attributed to the property of the absorber and its surrounding material in the redeposition layer, which is different from those in the subsurface Damage layer. The Damage growth characteristics of the two morphologies are measured, and the size of crater increases under successive shots, but the size of the gray haze remains constant. The growth of the crater is attributed to the existence of crack around the absorber, which is observed by SEM imaging. On the basis of the above analysis, the schematic diagram of subsurface feature is discussed. Copyright © 2010 John Wiley & Sons, Ltd.
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laser induced Damage Morphology of high reflective optical coatings
Applied Surface Science, 2005Co-Authors: Zhiping Tang, Zhengxiu Fan, Jianda ShaoAbstract:Two different kinds of 1064 nm high-reflective (HR) coatings, with and without SiO2 protective layer, were prepared by electron beam evaporation. Three-dimensional Damage Morphology, caused by a Nd:YAG pulsed laser, was investigated for these HR coatings. Development of laser-induced Damage on HR coatings was revealed by both temperature field calculation and discrete meso-element simulation. Theoretical results met experimental very well. (C) 2004 Elsevier B.V. All rights reserved.
Kyle Kafka - One of the best experts on this subject based on the ideXlab platform.
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few cycle pulse laser induced Damage threshold determination of ultra broadband optics
Optics Express, 2016Co-Authors: Kyle Kafka, Noah Talisa, G Tempea, Drake R Austin, Catalin C Neacsu, Enam ChowdhuryAbstract:A systematic study of few-cycle pulse laser induced Damage threshold (LIDT) determination was performed for commercially-available ultra-broadband optics, (i.e. chirped mirrors, silver mirrors, beamsplitters, etc.) in vacuum and in air, for single and multi-pulse regime (S-on-1). Multi-pulse Damage Morphology at fluences below the single-pulse LIDT was studied in order to investigate the mechanisms leading to the onset of Damage. Stark morphological contrast was observed between multi-pulse Damage sites formed in air versus those in vacuum. One effect of vacuum testing compared to air included suppression of laser-induced periodic surface structures (LIPSS) formation, possibly influenced by a reduced presence of Damage debris. Another effect of vacuum was occasional lowering of LIDT, which appears to be due to the stress-strain performance of the coating design during laser irradiation and under the external stress of vacuum ambience. A fused silica substrate is also examined, and a non-LIPSS nanostructuring is observed on the surface. Possible mechanisms are discussed.
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few cycle pulse laser induced Damage of thin films in air and vacuum ambience
Laser-Induced Damage in Optical Materials 2016, 2016Co-Authors: Kyle Kafka, Noah Talisa, G Tempea, Drake R Austin, Catalin C Neacsu, Enam ChowdhuryAbstract:Laser-induced Damage mechanisms were investigated for an ultra-broadband chirped mirror, as part of a systematic study of few-cycle pulse laser-induced Damage threshold (LIDT) of widely-used ultra-broadband optics, in vacuum and in air, for single and multi-pulse regimes (S-on-1). Microscopic analysis of Damage Morphology suggests that three different Damage mechanisms occur across the fluence range 0.15-0.4J/cm2, while no ablation was yet observed. The three regimes resulted in shallow swelling (< 10 nm tall), tall blistering (~ 150 nm tall), and annular blistering (Damage suppressed at highest intensity, forming a ring shape). Descriptions of the potential mechanisms are discussed.
Christopher W. Carr - One of the best experts on this subject based on the ideXlab platform.
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The role of defects in laser-induced modifications of silica coatings and fused silica using picosecond pulses at 1053 nm: I. Damage Morphology.
Optics express, 2017Co-Authors: Nan Shen, Christopher W. Carr, Raluca A. Negres, David Alessi, J. D. Bude, Amy L. Rigatti, Ted A. LaurenceAbstract:Laser-induced Damage with ps pulse widths straddles the transition from intrinsic, multi-photon ionization and avalanche ionization-based ablation with fs pulses to defect-dominated, thermal-based Damage with ns pulses. We investigated the Morphology of Damage for fused silica and silica coatings between 1 ps and 60 ps at 1053 nm. Using calibrated laser-induced Damage experiments, in situ imaging, and high-resolution optical microscopy, atomic force microscopy, and scanning electron microscopy, we show that defects play an important role in laser-induced Damage down to 1 ps. Three types of Damage are observed: ablation craters, ultra-high density pits, and smooth, circular depressions with central pits. For 10 ps and longer, the smooth, circular depressions limit the Damage performance of fused silica and silica coatings. The observed high-density pits and material removal down to 3 ps indicate that variations in surface properties limit the laser-induced Damage onset to a greater extent than expected below 60 ps. Below 3 ps, Damage craters are smoother although there is still evidence as seen by AFM of inhomogeneous laser-induced Damage response very near the Damage onset. These results show that modeling the Damage onset only as a function of pulse width does not capture the convoluted processes leading to laser induced Damage with ps pulses. It is necessary to account for the effects of defects on the processes leading to laser-induced Damage. The effects of isolated defects or inhomogeneities are most pronounced above 3 ps but are still discernible and possibly important down to the shortest pulse width investigated here.
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Growth behavior of laser-induced Damage on fused silica optics under UV, ns laser irradiation
Optics Express, 2010Co-Authors: Raluca A. Negres, David A. Cross, Mary A Norton, Christopher W. CarrAbstract:The growth behavior of laser-induced Damage sites is affected by a large number of laser parameters as well as site Morphology. Here we investigate the effects of pulse duration on the growth rate of Damage sites located on the exit surface of fused silica optics. Results demonstrate a significant dependence of the growth parameters on laser pulse duration at 351 nm from 1 ns to 15 ns, including the observation of a dominant exponential versus linear, multiple-shot growth behavior for long and short pulses, respectively. These salient behaviors are tied to the Damage Morphology and suggest a shift in the fundamental growth mechanisms for pulses in the 1-5 ns range.
