We discuss studies of laser damage inside various transparent materials (glasses, polymers, sapphire, diamond) caused by femtosecond lasers at 515, 800, and 1030 nm, with nJ to mJ pulse energies, single-shot to 2 MHz repetition rates, single and 10 ns burst-mode pulses, chirped pulses, and linear, circular, and radial beam polarizations. Experiments have created high-aspect damage features and voids using aberration-controlled focusing, axicon-formed Bessel beams with <1 μm diameter central lobes extending hundreds of microns through the materials, and tightly focused lines (~1 μm × <100 μm). Mechanisms include self-focusing, filamentation, and material expansion/compaction and expulsion.
{"title":"High-aspect ratio damage and modification in transparent materials by tailored focusing of femtosecond lasers","authors":"B. Canfield, A. Terekhov, L. Costa, L. Davis","doi":"10.1117/12.2536450","DOIUrl":"https://doi.org/10.1117/12.2536450","url":null,"abstract":"We discuss studies of laser damage inside various transparent materials (glasses, polymers, sapphire, diamond) caused by femtosecond lasers at 515, 800, and 1030 nm, with nJ to mJ pulse energies, single-shot to 2 MHz repetition rates, single and 10 ns burst-mode pulses, chirped pulses, and linear, circular, and radial beam polarizations. Experiments have created high-aspect damage features and voids using aberration-controlled focusing, axicon-formed Bessel beams with <1 μm diameter central lobes extending hundreds of microns through the materials, and tightly focused lines (~1 μm × <100 μm). Mechanisms include self-focusing, filamentation, and material expansion/compaction and expulsion.","PeriodicalId":202227,"journal":{"name":"Laser Damage","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127035895","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
E. Field, B. Galloway, D. Kletecka, P. Rambo, I. Smith
Dichroic coatings have been developed for high transmission at 527 nm and high reflection at 1054 nm for laser operations in the nanosecond pulse regime. The coatings consist of HfO2 and SiO2 layers deposited with e-beam evaporation, and laser-induced damage thresholds as high as 12.5 J/cm2 were measured at 532 nm with 3.5 ns pulses (22.5 degrees angle of incidence, in S-polarization). However, laser damage measurements at the single wavelength of 532 nm do not adequately characterize the laser damage resistance of these coatings, since they were designed to operate at dual wavelengths simultaneously. This became apparent after one of the coatings damaged prematurely at a lower fluence in the beam train, which inspired further investigations. To gain a more complete understanding of the laser damage resistance, results of a dual-wavelength laser damage test performed at both 532 nm and 1064 nm are presented.
{"title":"Dual-wavelength laser-induced damage threshold of a HfO2/SiO2 dichroic coating developed for high transmission at 527 nm and high reflection at 1054 nm","authors":"E. Field, B. Galloway, D. Kletecka, P. Rambo, I. Smith","doi":"10.1117/12.2536417","DOIUrl":"https://doi.org/10.1117/12.2536417","url":null,"abstract":"Dichroic coatings have been developed for high transmission at 527 nm and high reflection at 1054 nm for laser operations in the nanosecond pulse regime. The coatings consist of HfO2 and SiO2 layers deposited with e-beam evaporation, and laser-induced damage thresholds as high as 12.5 J/cm2 were measured at 532 nm with 3.5 ns pulses (22.5 degrees angle of incidence, in S-polarization). However, laser damage measurements at the single wavelength of 532 nm do not adequately characterize the laser damage resistance of these coatings, since they were designed to operate at dual wavelengths simultaneously. This became apparent after one of the coatings damaged prematurely at a lower fluence in the beam train, which inspired further investigations. To gain a more complete understanding of the laser damage resistance, results of a dual-wavelength laser damage test performed at both 532 nm and 1064 nm are presented.","PeriodicalId":202227,"journal":{"name":"Laser Damage","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134069597","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The laser-induced damage performance of fused silica optics when exposed to 351-nm ns pulses is a limiting factor in the design and operation of most high-energy laser systems. As such, significant effort has been expended in developing laser damage testing protocols and procedures to inform laser system design and operating limits. These tests typically rely on multiple laser exposures for statistical validation. For larger aperture systems testing an area equal to that of the optical components in the system is functionally impossible requiring interrogation of sub-scale witness samples with elevated fluences. In this work, we show that, under the certain circumstances, the laser exposure used to test one location on a sample will generate additional laser-induced damage precursors in regions beyond that exposed to laser light and hence degrade the damage performance observed on subsequent exposures. In addition, we will outline the conditions under which this phenomenon occurs, as well as methods for mitigating or eliminating the effect.
{"title":"Creation of high-fluence precursors by 351-nm laser exposure on SiO2 substrates","authors":"D. Cross, C. Carr","doi":"10.1117/12.2536507","DOIUrl":"https://doi.org/10.1117/12.2536507","url":null,"abstract":"The laser-induced damage performance of fused silica optics when exposed to 351-nm ns pulses is a limiting factor in the design and operation of most high-energy laser systems. As such, significant effort has been expended in developing laser damage testing protocols and procedures to inform laser system design and operating limits. These tests typically rely on multiple laser exposures for statistical validation. For larger aperture systems testing an area equal to that of the optical components in the system is functionally impossible requiring interrogation of sub-scale witness samples with elevated fluences. In this work, we show that, under the certain circumstances, the laser exposure used to test one location on a sample will generate additional laser-induced damage precursors in regions beyond that exposed to laser light and hence degrade the damage performance observed on subsequent exposures. In addition, we will outline the conditions under which this phenomenon occurs, as well as methods for mitigating or eliminating the effect.","PeriodicalId":202227,"journal":{"name":"Laser Damage","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115728030","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
J. Vanda, M. Mureșan, P. Čech, Martin Mydlář, A. Lucianetti, J. Brajer, T. Mocek, V. Škoda, S. Uxa
Optical glasses, in particular fused silica and BK7, are the most common and used substrates for components manufacturing in laser technology and optics in general. Dielectric coating technologies for those materials are well known and established; both high-reflective and anti-reflective coatings prepared on such substrates demonstrated laser induced damage threshold (LIDT) exceeding tens J·cm-2 in nanosecond regime. However, LIDT became a major issue in further exploitation of crystalline materials as yttrium aluminum garnet (YAG) crystals, which often serves as a host in laser media and would be used in other components as well. One of the current challenge is the ability to transfer thin film coating technology used on glass to YAG in order to reach the same performance as in the case of fused silica or BK7 counterparts. HR dielectric coatings prepared on fused silica, BK7 and YAG substrates by reactive or ion-assisted e-beam deposition technique were tested on LIDT by s-on-1 method according to the ISO standard recommendations. Results from tests are presented and discussed in following paper.
{"title":"Comparison of multipulse nanosecond LIDT of HR coated YAG and glass substrates at 1030 nm","authors":"J. Vanda, M. Mureșan, P. Čech, Martin Mydlář, A. Lucianetti, J. Brajer, T. Mocek, V. Škoda, S. Uxa","doi":"10.1117/12.2536433","DOIUrl":"https://doi.org/10.1117/12.2536433","url":null,"abstract":"Optical glasses, in particular fused silica and BK7, are the most common and used substrates for components manufacturing in laser technology and optics in general. Dielectric coating technologies for those materials are well known and established; both high-reflective and anti-reflective coatings prepared on such substrates demonstrated laser induced damage threshold (LIDT) exceeding tens J·cm-2 in nanosecond regime. However, LIDT became a major issue in further exploitation of crystalline materials as yttrium aluminum garnet (YAG) crystals, which often serves as a host in laser media and would be used in other components as well. One of the current challenge is the ability to transfer thin film coating technology used on glass to YAG in order to reach the same performance as in the case of fused silica or BK7 counterparts. HR dielectric coatings prepared on fused silica, BK7 and YAG substrates by reactive or ion-assisted e-beam deposition technique were tested on LIDT by s-on-1 method according to the ISO standard recommendations. Results from tests are presented and discussed in following paper.","PeriodicalId":202227,"journal":{"name":"Laser Damage","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128790637","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
T. Kumazaki, Daisuke Tei, M. Hattori, Yousuke Fujimaki, J. Fujimoto, H. Mizoguchi
In the semiconductor industry, optical projection lithography is employed for the production of microchips. In this process ultraviolet radiation has been used to exposure of photoresists on silicon wafers. Light sources with shorter wavelength are needed to shrink the chip size due to the diffraction limit. Pulsed excimer lasers have been used since the middle of 1990s instead of mercury lamps. At first KrF lasers (248-nm) were adopted, then ArF lasers (193-nm) have been applied to satisfy tighter leading edge device requirements. Now almost 5,000 excimer lasers for lithography tools are being operated at the world-wide semiconductor fab with stable, its availability up to 99.8%. The latest ArF excimer laser can pulse 15mJ to 20mJ energy with 6-kHz repetition rate, its typical module lifetime which can be replaced is several dozen Billion pulses. The module lifetime are expected to expand to reduce the downtime to replace. Also for precise micromachining applications, ArF hybrid laser consists of all-solid-state DUV light source as a seed laser and excimer laser as amplifier is been developed. The pulse width of this laser is typically sub-nanosecond and its high peak power is another concern for laser optics. Generally, the lifespan of optical elements has been growing to reach 100 Bpls, and its evaluation takes a very long time, typically several years. Comprehensive durability evaluation becomes more efficient by creating accelerated element tests [1]. As an alternative, accelerated lifetime testing with high fluence are helpful approach to screen and select the optics to satisfy the lifetime requirement. We have been developing the accelerated test system to determinate the laser-induced damage threshold of optical surfaces. In this paper, the test system and some results of field-approved optics with 20ns pulse duration will be explained.
{"title":"Laser-induced damage threshold by high pulse repetition rate ArF excimer laser radiation","authors":"T. Kumazaki, Daisuke Tei, M. Hattori, Yousuke Fujimaki, J. Fujimoto, H. Mizoguchi","doi":"10.1117/12.2536268","DOIUrl":"https://doi.org/10.1117/12.2536268","url":null,"abstract":"In the semiconductor industry, optical projection lithography is employed for the production of microchips. In this process ultraviolet radiation has been used to exposure of photoresists on silicon wafers. Light sources with shorter wavelength are needed to shrink the chip size due to the diffraction limit. Pulsed excimer lasers have been used since the middle of 1990s instead of mercury lamps. At first KrF lasers (248-nm) were adopted, then ArF lasers (193-nm) have been applied to satisfy tighter leading edge device requirements. Now almost 5,000 excimer lasers for lithography tools are being operated at the world-wide semiconductor fab with stable, its availability up to 99.8%. The latest ArF excimer laser can pulse 15mJ to 20mJ energy with 6-kHz repetition rate, its typical module lifetime which can be replaced is several dozen Billion pulses. The module lifetime are expected to expand to reduce the downtime to replace. Also for precise micromachining applications, ArF hybrid laser consists of all-solid-state DUV light source as a seed laser and excimer laser as amplifier is been developed. The pulse width of this laser is typically sub-nanosecond and its high peak power is another concern for laser optics. Generally, the lifespan of optical elements has been growing to reach 100 Bpls, and its evaluation takes a very long time, typically several years. Comprehensive durability evaluation becomes more efficient by creating accelerated element tests [1]. As an alternative, accelerated lifetime testing with high fluence are helpful approach to screen and select the optics to satisfy the lifetime requirement. We have been developing the accelerated test system to determinate the laser-induced damage threshold of optical surfaces. In this paper, the test system and some results of field-approved optics with 20ns pulse duration will be explained.","PeriodicalId":202227,"journal":{"name":"Laser Damage","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114526283","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Weili Zhang, Zhenkun Yu, Ruijuan Zhu, Xiaofeng Liu, Kui Yi, Meiping Zhu, J. Shao
Vacuum ultraviolet (VUV) reflective coatings play an important role in many high-tech fields including cosmic physics, space research, life science and synchrotron radiation. In this research, the emphasis are focused on the aging effect of 135.6nm high reflective coatings. The coatings were deposited by resistive heating method based on Lanthanum fluoride (LaF3) and Aluminum fluoride (AlF3). Optical property, surface morphology and roughness, and composition were characterized in different period after deposited. Due to the porous structure and the worse stability of lanthanum fluoride, the content of C and O element increased in LaF3 thin films during aging process. On one hand, the content of C and O are the hydrocarbon contamination from environment and packing boxes. On the other hand, due to the oxidation of film materials, the fluorides will turn into oxyfluoride, which will increase O content. As a result, there will be an increase of absorption and a decrease of reflectance of the 135.6nm high reflective coating. The surface roughness decreased which led to the reduction of scattering and the rise of reflectivity. There will be LaF3-AlF3 mixed layers between interfaces because of interface diffusion, which will further reduce the film performance.
{"title":"Stability of dielectric multilayer coatings for the Vacuum ultraviolet","authors":"Weili Zhang, Zhenkun Yu, Ruijuan Zhu, Xiaofeng Liu, Kui Yi, Meiping Zhu, J. Shao","doi":"10.1117/12.2536346","DOIUrl":"https://doi.org/10.1117/12.2536346","url":null,"abstract":"Vacuum ultraviolet (VUV) reflective coatings play an important role in many high-tech fields including cosmic physics, space research, life science and synchrotron radiation. In this research, the emphasis are focused on the aging effect of 135.6nm high reflective coatings. The coatings were deposited by resistive heating method based on Lanthanum fluoride (LaF3) and Aluminum fluoride (AlF3). Optical property, surface morphology and roughness, and composition were characterized in different period after deposited. Due to the porous structure and the worse stability of lanthanum fluoride, the content of C and O element increased in LaF3 thin films during aging process. On one hand, the content of C and O are the hydrocarbon contamination from environment and packing boxes. On the other hand, due to the oxidation of film materials, the fluorides will turn into oxyfluoride, which will increase O content. As a result, there will be an increase of absorption and a decrease of reflectance of the 135.6nm high reflective coating. The surface roughness decreased which led to the reduction of scattering and the rise of reflectivity. There will be LaF3-AlF3 mixed layers between interfaces because of interface diffusion, which will further reduce the film performance.","PeriodicalId":202227,"journal":{"name":"Laser Damage","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127908289","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The continuous wave laser-induced damage thresholds of Schott chalcogenide glasses, IRG-24, IRG-25, and IRG-26, are measured for a 5s exposure of 1.07 μm light focused to a spot size with 1/e2 diameter of 830 μm, following the International Organization for Standardization standards.
{"title":"Continuous wave laser-induced damage threshold of Schott IRG-24, IRG-25, and IRG-26 at 1.07 microns","authors":"J. McElhenny, N. Bambha","doi":"10.1117/12.2532062","DOIUrl":"https://doi.org/10.1117/12.2532062","url":null,"abstract":"The continuous wave laser-induced damage thresholds of Schott chalcogenide glasses, IRG-24, IRG-25, and IRG-26, are measured for a 5s exposure of 1.07 μm light focused to a spot size with 1/e2 diameter of 830 μm, following the International Organization for Standardization standards.","PeriodicalId":202227,"journal":{"name":"Laser Damage","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130885623","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
F. Wagner, G. Gebrayel El Reaidy, D. Faye, J. Natoli
"Laser-induced contamination" is a major difficulty for high power photonics instruments in vacuum and in sealed environments. Material outgassing causes molecular contamination on the optical components where the laser irradiation causes photo-fixation and/or polymerization leading to carbonaceous deposits at the location of the laser beam. We studied the morphology of these deposits as function of several parameters of physical and chemical nature. The influence of these parameters on the crater rim height of the "donut"-type deposits are presented and lateral growth of the deposits beyond the laser beam size is observed. The observation of lateral growth beyond the laser beam size indicates an influence of thermal energy input to the deposition process. We hypothesize that this thermal energy is provided by heat conduction from the center of the crater.
{"title":"UV-laser-induced contamination: a parametric study of deposit morphology","authors":"F. Wagner, G. Gebrayel El Reaidy, D. Faye, J. Natoli","doi":"10.1117/12.2538961","DOIUrl":"https://doi.org/10.1117/12.2538961","url":null,"abstract":"\"Laser-induced contamination\" is a major difficulty for high power photonics instruments in vacuum and in sealed environments. Material outgassing causes molecular contamination on the optical components where the laser irradiation causes photo-fixation and/or polymerization leading to carbonaceous deposits at the location of the laser beam. We studied the morphology of these deposits as function of several parameters of physical and chemical nature. The influence of these parameters on the crater rim height of the \"donut\"-type deposits are presented and lateral growth of the deposits beyond the laser beam size is observed. The observation of lateral growth beyond the laser beam size indicates an influence of thermal energy input to the deposition process. We hypothesize that this thermal energy is provided by heat conduction from the center of the crater.","PeriodicalId":202227,"journal":{"name":"Laser Damage","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115111231","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Several sets of fused silica and BK7 windows were anti-reflection (AR) coated for 1030 nm wavelength using ion assisted e-beam deposition under various conditions (substrate temperature, ion-beam energy). Samples were tested for laser-induced damage threshold (LIDT) at 1030 nm, 10 ns with 10 Hz repetition rate in 1000-on-1 mode according to ISO 21254 standard. Measured damage thresholds at normal (0 deg) incidence were compared and discussed.
{"title":"A study of ns-LIDT of ion-beam assisted coatings of optical windows","authors":"S. Uxa, J. Vanda, M. Mureșan, V. Škoda","doi":"10.1117/12.2536435","DOIUrl":"https://doi.org/10.1117/12.2536435","url":null,"abstract":"Several sets of fused silica and BK7 windows were anti-reflection (AR) coated for 1030 nm wavelength using ion assisted e-beam deposition under various conditions (substrate temperature, ion-beam energy). Samples were tested for laser-induced damage threshold (LIDT) at 1030 nm, 10 ns with 10 Hz repetition rate in 1000-on-1 mode according to ISO 21254 standard. Measured damage thresholds at normal (0 deg) incidence were compared and discussed.","PeriodicalId":202227,"journal":{"name":"Laser Damage","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114533998","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
N. Talisa, M. Tripepi, Brandon Harris, A. Alshafey, J. Krebs, A. Davenport, E. Randel, C. Menoni, E. Chowdhury
The pulse duration dependence of single-shot laser-induced damage and ablation of HfO2/SiO2-based double- and quadlayer thin films is studied using time-resolved surface microscopy (TRSM) and ex situ imaging down to the few-cycle pulse (FCP) regime. Both samples exhibit a raised, "blister" morphology for a range of fluences between the damage and ablation thresholds. The fluence range associated with blister formation is much larger for FCPs than for 110 fs pulses, and TRSM images at early time-delays show that the density of the laser-generated plasma is much higher for 110 fs pulses for a lower fluence relative to the damage threshold. Also, for high enough fluences the excited electron density exhibits a fast decay down to a significantly high value, which remains even after the onset of mechanical damage of the layers. The pulse duration dependence suggests that as fluence is increased, the increase in absorbed energy is more gradual for FCPs, which points towards inherent differences in the way high intensity FCPs are absorbed in dielectrics relative to longer femtosecond laser pulses.
{"title":"Single-shot femtosecond laser-induced damage and ablation of HfO2/SiO2-based optical thin films: a comparison between few-cycle pulses and 110 fs pulses","authors":"N. Talisa, M. Tripepi, Brandon Harris, A. Alshafey, J. Krebs, A. Davenport, E. Randel, C. Menoni, E. Chowdhury","doi":"10.1117/12.2536423","DOIUrl":"https://doi.org/10.1117/12.2536423","url":null,"abstract":"The pulse duration dependence of single-shot laser-induced damage and ablation of HfO2/SiO2-based double- and quadlayer thin films is studied using time-resolved surface microscopy (TRSM) and ex situ imaging down to the few-cycle pulse (FCP) regime. Both samples exhibit a raised, \"blister\" morphology for a range of fluences between the damage and ablation thresholds. The fluence range associated with blister formation is much larger for FCPs than for 110 fs pulses, and TRSM images at early time-delays show that the density of the laser-generated plasma is much higher for 110 fs pulses for a lower fluence relative to the damage threshold. Also, for high enough fluences the excited electron density exhibits a fast decay down to a significantly high value, which remains even after the onset of mechanical damage of the layers. The pulse duration dependence suggests that as fluence is increased, the increase in absorbed energy is more gradual for FCPs, which points towards inherent differences in the way high intensity FCPs are absorbed in dielectrics relative to longer femtosecond laser pulses.","PeriodicalId":202227,"journal":{"name":"Laser Damage","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131348023","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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