N. Ray, J. Yoo, Hoang T. Nguyen, Michael A. Johnson, E. Feigenbaum
Recent work utilizing metal etching masks to fabricate substrate-engraved metasurfaces have been handicapped by the available etching depth, restricting the bandwidth of antireflective performance. Advances made to etch mask technology to facilitate deeper etching will be discussed here, and the taller ensuant metasurface features will be presented. The antireflective performance of these high aspect ratio structures (broad acceptance angles and broadband antireflective performance for both polarizations) will be discussed.
{"title":"Glass-engraved metasurfaces: the path to ultra-low reflectance, extreme broadband performance, and high acceptance angle for high power laser applications","authors":"N. Ray, J. Yoo, Hoang T. Nguyen, Michael A. Johnson, E. Feigenbaum","doi":"10.1117/12.2641631","DOIUrl":"https://doi.org/10.1117/12.2641631","url":null,"abstract":"Recent work utilizing metal etching masks to fabricate substrate-engraved metasurfaces have been handicapped by the available etching depth, restricting the bandwidth of antireflective performance. Advances made to etch mask technology to facilitate deeper etching will be discussed here, and the taller ensuant metasurface features will be presented. The antireflective performance of these high aspect ratio structures (broad acceptance angles and broadband antireflective performance for both polarizations) will be discussed.","PeriodicalId":202227,"journal":{"name":"Laser Damage","volume":"50 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132194409","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}
Subwavelength, low-haze, anti-reflective (AR) nano-textured surfaces are an effective replacement for thin-film AR coatings (TFARCs) with the potential to increase reliability and minimize thermo-optic effects in kW-class diamond-based laser systems. Etched directly into optical surfaces, AR nano-textured surfaces can yield high optical damage resistance combined with high transmission, low back reflection, and low absorption values equivalent to the bulk substrate material. In this initial study, Random AR (RAR) nano-structures were etched into monocrystalline chemical vapor deposited (CVD) diamond windows. Photothermal common-path interferometry (PCI) measurements at 1064nm were conducted in order to characterize the level of absorption at the surfaces and through the bulk of diamond substrates. Nano-second pulsed laser induced damage threshold (LiDT) measurements at 1064nm were conducted, and damage sites were analyzed via scanning electron microscopy (SEM) to understand damage mechanisms in both as-polished and RAR nano-textured diamond samples.
{"title":"RAR nano-textured diamond pulsed LIDT","authors":"A. Manni, B. MacLeod, D. S. Hobbs","doi":"10.1117/12.2641596","DOIUrl":"https://doi.org/10.1117/12.2641596","url":null,"abstract":"Subwavelength, low-haze, anti-reflective (AR) nano-textured surfaces are an effective replacement for thin-film AR coatings (TFARCs) with the potential to increase reliability and minimize thermo-optic effects in kW-class diamond-based laser systems. Etched directly into optical surfaces, AR nano-textured surfaces can yield high optical damage resistance combined with high transmission, low back reflection, and low absorption values equivalent to the bulk substrate material. In this initial study, Random AR (RAR) nano-structures were etched into monocrystalline chemical vapor deposited (CVD) diamond windows. Photothermal common-path interferometry (PCI) measurements at 1064nm were conducted in order to characterize the level of absorption at the surfaces and through the bulk of diamond substrates. Nano-second pulsed laser induced damage threshold (LiDT) measurements at 1064nm were conducted, and damage sites were analyzed via scanning electron microscopy (SEM) to understand damage mechanisms in both as-polished and RAR nano-textured diamond samples.","PeriodicalId":202227,"journal":{"name":"Laser Damage","volume":"57 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116107908","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}
M. Steinecke, K. Kiedrowski, M. Jupé, A. Wienke, D. Ristau
We demonstrate a novel concept for an all-optical switch based on the optical Kerr-effect in thin film interference coatings. The switching between transmittance and reflectance relies on highly Kerr-active coating materials in combination with large internal intensity enhancement in thin film interference coatings. The paper investigates the switching performance as well as its relation to the laser induced damage threshold of these novel components. A modulation depth of 30 % was achieved without damage to the component, which very promising for later applications as power limiters or mode locking components.
{"title":"Nonlinear optical switching in thin film coatings in relation to the damage threshold","authors":"M. Steinecke, K. Kiedrowski, M. Jupé, A. Wienke, D. Ristau","doi":"10.1117/12.2642756","DOIUrl":"https://doi.org/10.1117/12.2642756","url":null,"abstract":"We demonstrate a novel concept for an all-optical switch based on the optical Kerr-effect in thin film interference coatings. The switching between transmittance and reflectance relies on highly Kerr-active coating materials in combination with large internal intensity enhancement in thin film interference coatings. The paper investigates the switching performance as well as its relation to the laser induced damage threshold of these novel components. A modulation depth of 30 % was achieved without damage to the component, which very promising for later applications as power limiters or mode locking components.","PeriodicalId":202227,"journal":{"name":"Laser Damage","volume":"2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121539725","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. Willemsen, T. Gross, M. Gauch, H. Ehlers, D. Kramer, P. Velpula, W. Ebert
Latest advances of high intensity laser facilities enable the beam transport of petawatt laser pulses and can provide novel fundamental insights in high energy plasma physics or laser fusion. The very high peak intensities put enormous demands on the required large sized optics. Beam transport mirrors reflect pulses with only several tens of fs and maintain their phase while providing best possible laser induced damage threshold. State of the art, such mirrors are mostly manufactured by thermal evaporation techniques as they provide a large and uniform deposition area. Their porous layer structure causes changing spectral characteristics and wavefront when vacuum-air cycled. Especially large sized mirrors can show crazing and thereby decrease up-time of PW beamlines. In contrast, sputtered layers are very compact and provide non changing characteristics. Stable and reproducible sputter processes enable the deposition of more complex design structures necessary for further optimization of the laser induced damage threshold. However, deposition rate is slow and an uniform large sized area difficult to achieve for sputtered coatings. In our study, we show a self-constructed and built-up ion beam sputtering (IBS) machine capable to deposit large sized substrates up to a diameter of 550 mm. A design study is presented to evaluate best HR810nm mirror to meet demanding spectral requirements and providing maximized laser damage threshold for HAPLS at ELI beamlines. In the end, a field optimized design is applied with a measured LIDT of 0.9 J/cm2 at 42 fs and 1 kHz. This design is used to manufacture beam transport mirrors for HAPLS applying IBS.
{"title":"Comparison of high power sputtered dielectric mirrors for PW laser","authors":"T. Willemsen, T. Gross, M. Gauch, H. Ehlers, D. Kramer, P. Velpula, W. Ebert","doi":"10.1117/12.2642134","DOIUrl":"https://doi.org/10.1117/12.2642134","url":null,"abstract":"Latest advances of high intensity laser facilities enable the beam transport of petawatt laser pulses and can provide novel fundamental insights in high energy plasma physics or laser fusion. The very high peak intensities put enormous demands on the required large sized optics. Beam transport mirrors reflect pulses with only several tens of fs and maintain their phase while providing best possible laser induced damage threshold. State of the art, such mirrors are mostly manufactured by thermal evaporation techniques as they provide a large and uniform deposition area. Their porous layer structure causes changing spectral characteristics and wavefront when vacuum-air cycled. Especially large sized mirrors can show crazing and thereby decrease up-time of PW beamlines. In contrast, sputtered layers are very compact and provide non changing characteristics. Stable and reproducible sputter processes enable the deposition of more complex design structures necessary for further optimization of the laser induced damage threshold. However, deposition rate is slow and an uniform large sized area difficult to achieve for sputtered coatings. In our study, we show a self-constructed and built-up ion beam sputtering (IBS) machine capable to deposit large sized substrates up to a diameter of 550 mm. A design study is presented to evaluate best HR810nm mirror to meet demanding spectral requirements and providing maximized laser damage threshold for HAPLS at ELI beamlines. In the end, a field optimized design is applied with a measured LIDT of 0.9 J/cm2 at 42 fs and 1 kHz. This design is used to manufacture beam transport mirrors for HAPLS applying IBS.","PeriodicalId":202227,"journal":{"name":"Laser Damage","volume":"132 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129220409","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}
M. Stehlik, J. Zideluns, F. Wagner, F. Lemarchand, Camille Petite, A. Moreau, A. Lereu, M. Minissale, J. Lumeau, L. Gallais
Laser-induced contamination (LIC) degrades the performance of optical components and can result in optical losses or even laser-induced damage. LIC deposit formation limits reliable operation of high repetition rate industrial lasers. In this work, we investigate LIC growth on dielectric oxide thin films in air environment irradiated by MHz sub-ps laser at 515 nm. We study the LIC growth dynamic in dependence on thin film deposition method, thin film material and thin film thickness.
{"title":"Sub-ps MHz green laser-induced contamination on dielectric coatings in air","authors":"M. Stehlik, J. Zideluns, F. Wagner, F. Lemarchand, Camille Petite, A. Moreau, A. Lereu, M. Minissale, J. Lumeau, L. Gallais","doi":"10.1117/12.2642516","DOIUrl":"https://doi.org/10.1117/12.2642516","url":null,"abstract":"Laser-induced contamination (LIC) degrades the performance of optical components and can result in optical losses or even laser-induced damage. LIC deposit formation limits reliable operation of high repetition rate industrial lasers. In this work, we investigate LIC growth on dielectric oxide thin films in air environment irradiated by MHz sub-ps laser at 515 nm. We study the LIC growth dynamic in dependence on thin film deposition method, thin film material and thin film thickness.","PeriodicalId":202227,"journal":{"name":"Laser Damage","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122424180","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}
Allison E. M. Browar, E. Feigenbaum, I. Bass, J. Vickers, G. Guss, W. Carr
We present the development of carefully tailored shape - increased size (0.9 mm diameter) input surface mitigation sites that shadow and thus supress damage growth on the exit surface of optics. Results from downstream intensification measurements and laser induced damage experiments are presented. The results show a 6X reduction in expanding wave intensification on the exit surface of an optic, being the dominant damage onset mechanism. The tailored rounded cone design can withstand over 30 J/cm2 sub aperture input surface fluence. A significant decrease in laser induced damage initiation and growth was observed compared to shadow cones with linear profiles at input fluences higher than 10 J/cm2.
{"title":"Development of a novel large damage site mitigation technique","authors":"Allison E. M. Browar, E. Feigenbaum, I. Bass, J. Vickers, G. Guss, W. Carr","doi":"10.1117/12.2642467","DOIUrl":"https://doi.org/10.1117/12.2642467","url":null,"abstract":"We present the development of carefully tailored shape - increased size (0.9 mm diameter) input surface mitigation sites that shadow and thus supress damage growth on the exit surface of optics. Results from downstream intensification measurements and laser induced damage experiments are presented. The results show a 6X reduction in expanding wave intensification on the exit surface of an optic, being the dominant damage onset mechanism. The tailored rounded cone design can withstand over 30 J/cm2 sub aperture input surface fluence. A significant decrease in laser induced damage initiation and growth was observed compared to shadow cones with linear profiles at input fluences higher than 10 J/cm2.","PeriodicalId":202227,"journal":{"name":"Laser Damage","volume":"90 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123550231","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}
I. Bass, E. Feigenbaum, R. Raman, K. Palma, J. Vickers, G. Guss, M. Norton, W. Carr
Exit surface damage on high value fused silica final optics on the NIF is sometimes too large to be mitigated with the currently used technique of removing the damage by CO2 laser machining a cone into the surface. To extend the service life of the optic, a 2 cm diameter shadow is created at the damage using a programmable spatial light modulator at the front end of the laser system. The use of this shadow technique is limited by the obscuration due to the large size of the shadow. An alternative approach is to create the shadow by machining a cone on the input surface opposite the damage. This reduces the shadow a rea, and thus the obscuration by several orders of magnitude. Additional benefits in service life of optics would be realized if the shadow cone size could be increased from current 600 m diameter. There are fabrication challenges encountered when the cone size is increased. To overcome this problem, the shadow performance of a hexagonal array of four 600 m diameter cones has been tested. We report on shadow leakage, bulk damage, and exit surface intensification issues presented by this array and techniques to address those issues.
{"title":"Performance of multiple cone arrays as shadow cone blockers on NIF","authors":"I. Bass, E. Feigenbaum, R. Raman, K. Palma, J. Vickers, G. Guss, M. Norton, W. Carr","doi":"10.1117/12.2642917","DOIUrl":"https://doi.org/10.1117/12.2642917","url":null,"abstract":"Exit surface damage on high value fused silica final optics on the NIF is sometimes too large to be mitigated with the currently used technique of removing the damage by CO2 laser machining a cone into the surface. To extend the service life of the optic, a 2 cm diameter shadow is created at the damage using a programmable spatial light modulator at the front end of the laser system. The use of this shadow technique is limited by the obscuration due to the large size of the shadow. An alternative approach is to create the shadow by machining a cone on the input surface opposite the damage. This reduces the shadow a rea, and thus the obscuration by several orders of magnitude. Additional benefits in service life of optics would be realized if the shadow cone size could be increased from current 600 m diameter. There are fabrication challenges encountered when the cone size is increased. To overcome this problem, the shadow performance of a hexagonal array of four 600 m diameter cones has been tested. We report on shadow leakage, bulk damage, and exit surface intensification issues presented by this array and techniques to address those issues.","PeriodicalId":202227,"journal":{"name":"Laser Damage","volume":"37 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124015227","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}
R. Negres, C. Stolz, S. DeFrances, D. Bernot, J. Randi, Jeffrey G. Thomas
This year’s competition proposed to survey the damage resistance of near-IR high reflectors designed for continuous-wave (CW) laser applications. The requirements for the coatings were a minimum reflection of 99.5% at normal incidence for 1077-nm light. The participants in this effort selected the coating materials, coating design, and deposition method. Samples were damage tested at a single testing facility using a kW fiber laser source capable of delivering up to 10 MW/cm2 peak irradiance on target. A double blind test assured sample and submitter anonymity. The damage performance results, sample rankings, details of the deposition processes, coating materials and substrate cleaning methods are shared. We found that multilayer coatings using tantala or hafnia as high index materials were top performers under CW laser exposure within several coating deposition groups. Namely, dense coatings by ion-beam sputtering (IBS), plasma-enhanced atomic layer deposition (PEALD) and magnetron sputtering (MS) exhibited the lowest absorption & temperature rise upon CW laser irradiation without damage onset up to the maximum power density level available in this study.
{"title":"1077-nm, CW mirror thin film damage competition","authors":"R. Negres, C. Stolz, S. DeFrances, D. Bernot, J. Randi, Jeffrey G. Thomas","doi":"10.1117/12.2641371","DOIUrl":"https://doi.org/10.1117/12.2641371","url":null,"abstract":"This year’s competition proposed to survey the damage resistance of near-IR high reflectors designed for continuous-wave (CW) laser applications. The requirements for the coatings were a minimum reflection of 99.5% at normal incidence for 1077-nm light. The participants in this effort selected the coating materials, coating design, and deposition method. Samples were damage tested at a single testing facility using a kW fiber laser source capable of delivering up to 10 MW/cm2 peak irradiance on target. A double blind test assured sample and submitter anonymity. The damage performance results, sample rankings, details of the deposition processes, coating materials and substrate cleaning methods are shared. We found that multilayer coatings using tantala or hafnia as high index materials were top performers under CW laser exposure within several coating deposition groups. Namely, dense coatings by ion-beam sputtering (IBS), plasma-enhanced atomic layer deposition (PEALD) and magnetron sputtering (MS) exhibited the lowest absorption & temperature rise upon CW laser irradiation without damage onset up to the maximum power density level available in this study.","PeriodicalId":202227,"journal":{"name":"Laser Damage","volume":"19 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132429162","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}
Christopher F. Miller, D. Cross, J. Senecal, R. Clark, C. Amorin, L. Kegelmeyer, C. Carr, Ernest Truscott
Identifying laser induced damage on the surface of optical components for the purpose of tracking its growth over time and repairing it is an important part of the economical operation of the National Ignition Facility (NIF). Optics installed on NIF are monitored in situ for damage growth and can be removed as needed for repair and re-use. An ex-situ automated microscopy system is used to inspect full sized NIF optics allowing for the detection of damage sites <10 μm in diameter. Due to the various morphology of laser damage, several algorithms are used to analyze the microscopy data and identify damage regardless of size, while ignoring features not related to laser damage. This system has significantly increased the lifetime of NIF final optics (≈2.3x) thereby extending beyond the capabilities of the in-situ inspection by itself.
{"title":"An automated damage inspection microscopy system for National Ignition Facility optics","authors":"Christopher F. Miller, D. Cross, J. Senecal, R. Clark, C. Amorin, L. Kegelmeyer, C. Carr, Ernest Truscott","doi":"10.1117/12.2642181","DOIUrl":"https://doi.org/10.1117/12.2642181","url":null,"abstract":"Identifying laser induced damage on the surface of optical components for the purpose of tracking its growth over time and repairing it is an important part of the economical operation of the National Ignition Facility (NIF). Optics installed on NIF are monitored in situ for damage growth and can be removed as needed for repair and re-use. An ex-situ automated microscopy system is used to inspect full sized NIF optics allowing for the detection of damage sites <10 μm in diameter. Due to the various morphology of laser damage, several algorithms are used to analyze the microscopy data and identify damage regardless of size, while ignoring features not related to laser damage. This system has significantly increased the lifetime of NIF final optics (≈2.3x) thereby extending beyond the capabilities of the in-situ inspection by itself.","PeriodicalId":202227,"journal":{"name":"Laser Damage","volume":"238 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132592035","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}
M. Stehlik, G. Govindassamy, J. Zideluns, F. Lemarchand, F. Wagner, J. Lumeau, J. Mackenzie, L. Gallais
Crystalline sesquioxide films (Sc2O3, Y2O3, Lu2O3) produced by pulsed-laser deposition were examined for laser damage resistance with pulses of 500 fs duration, at a wavelength of 1030 nm and at a 10 Hz repetition rate. Comparable tests were performed with amorphous magnetron-sputtered thin films (SiO2, HfO2, Nb2O5). We found the laser-induced damage thresholds of the sesquioxides are close to those of HfO2 in the multi-pulse test regime. The results are the basis for designs of damage resistant re ective components used in ultrashort-pulse lasers.
{"title":"Sub-ps 1030 nm laser-induced damage threshold evaluation of pulsed-laser deposited sesquioxides and magnetron-sputtered metal oxide optical coatings","authors":"M. Stehlik, G. Govindassamy, J. Zideluns, F. Lemarchand, F. Wagner, J. Lumeau, J. Mackenzie, L. Gallais","doi":"10.1117/12.2641792","DOIUrl":"https://doi.org/10.1117/12.2641792","url":null,"abstract":"Crystalline sesquioxide films (Sc2O3, Y2O3, Lu2O3) produced by pulsed-laser deposition were examined for laser damage resistance with pulses of 500 fs duration, at a wavelength of 1030 nm and at a 10 Hz repetition rate. Comparable tests were performed with amorphous magnetron-sputtered thin films (SiO2, HfO2, Nb2O5). We found the laser-induced damage thresholds of the sesquioxides are close to those of HfO2 in the multi-pulse test regime. The results are the basis for designs of damage resistant re ective components used in ultrashort-pulse lasers.","PeriodicalId":202227,"journal":{"name":"Laser Damage","volume":"29 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131703976","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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