C. Amra, C. Deumié, G. Georges, L. Arnaud, M. Zerrad, C. Grèzes-besset, F. Chazallet
A recent optical technique is reviewed to identify the scattering origins (surface roughness or bulk heterogeneities) and eliminate scattering sources in a selective way. Applications concern the field of optical interference coatings, remote sensing and imaging in random media.
{"title":"Selective cancellation of scattered light in optical substrates and coatings","authors":"C. Amra, C. Deumié, G. Georges, L. Arnaud, M. Zerrad, C. Grèzes-besset, F. Chazallet","doi":"10.1117/12.752717","DOIUrl":"https://doi.org/10.1117/12.752717","url":null,"abstract":"A recent optical technique is reviewed to identify the scattering origins (surface roughness or bulk heterogeneities) and eliminate scattering sources in a selective way. Applications concern the field of optical interference coatings, remote sensing and imaging in random media.","PeriodicalId":204978,"journal":{"name":"SPIE Laser Damage","volume":"3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132338704","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}
L. Jensen, M. Jupé, K. Starke, D. Ristau, W. Riede, P. Allenspacher
The ISO 11254 standard for LIDT tests suggests two possible spatial beam profiles for damage testing. Accordingly, an equal set of samples was tested with a Gaussian TEM00 as well as with a top-hat beam profile at different beam diameters. It was found that for the investigated HfO2/SiO2 high reflectors there was no threshold dependence on the beam diameter at 355nm. The damage threshold values measured with the Gaussian and the top-hat beam were in good correlation.
ISO 11254 LIDT测试标准提出了两种可能用于损伤测试的空间梁廓形。因此，在不同光束直径下，用高斯TEM00和顶帽光束轮廓测试了一组相等的样品。研究发现，对于所研究的HfO2/SiO2高反射镜，在355nm处光束直径没有阈值依赖性。用高斯函数和顶帽梁测量的损伤阈值具有良好的相关性。
{"title":"Comparison of Gaussian and top-hat beam profiles in LIDT testing","authors":"L. Jensen, M. Jupé, K. Starke, D. Ristau, W. Riede, P. Allenspacher","doi":"10.1117/12.752873","DOIUrl":"https://doi.org/10.1117/12.752873","url":null,"abstract":"The ISO 11254 standard for LIDT tests suggests two possible spatial beam profiles for damage testing. Accordingly, an equal set of samples was tested with a Gaussian TEM00 as well as with a top-hat beam profile at different beam diameters. It was found that for the investigated HfO2/SiO2 high reflectors there was no threshold dependence on the beam diameter at 355nm. The damage threshold values measured with the Gaussian and the top-hat beam were in good correlation.","PeriodicalId":204978,"journal":{"name":"SPIE Laser Damage","volume":"24 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133116807","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. Andrew, M. Girling, Nicholas Honiatt, D. Scott, P. Wallace
In this paper we review contamination and damage that has occurred since the HELEN laser was converted for use as a chirped pulse amplification (CPA) system. We concentrate on the largest components in the facility that operated in a vacuum environment in the short pulse (500fs) parts of the system. This experience will be valuable for planning commissioning and operations on the successor facility, ORION that is currently being constructed. The optical components located in the vacuum sections will be described. We have an interest in laser-induced damage and contamination from the long pulse only (~1ns), short pulse only (500fs) and combined regimes. For most of the operations the CPA system has operated at a wavelength of 1053nm (1ω). Some experiments have also been conducted with 527nm (2ω) CPA light derived by the use of a KDP doubling crystal. Damage to the infra red pulse compression gratings has occurred infrequently with a minority of high-energy shots. Contamination of multilayer dielectric plane turning mirrors has arisen from target disassembly. Focussing systems using off axis parabolic mirrors have sustained contamination from debris and a dielectric protected silver reflector used for green light suffered laser induced damage. Debris shields placed between the target and the parabolas have been used on selected experiments. The shields were anti-reflection coated with single layer, sol gel silica. These shields became contaminated on the target facing sides and in the case of 2ω operation also from blow off of the damaged mirror coating that caused a two-pass transmission loss in the system. A number of characterisation methods were used to evaluate and quantify the damage and contamination. These include macroscopic photography, microscopy, reflectometry and transmission spectroscopy.
{"title":"Operational experience of contamination and damage of the larger aperture optics in the HELEN laser facility vacuum system at 1053 and 527 nanometres","authors":"J. Andrew, M. Girling, Nicholas Honiatt, D. Scott, P. Wallace","doi":"10.1117/12.746743","DOIUrl":"https://doi.org/10.1117/12.746743","url":null,"abstract":"In this paper we review contamination and damage that has occurred since the HELEN laser was converted for use as a chirped pulse amplification (CPA) system. We concentrate on the largest components in the facility that operated in a vacuum environment in the short pulse (500fs) parts of the system. This experience will be valuable for planning commissioning and operations on the successor facility, ORION that is currently being constructed. The optical components located in the vacuum sections will be described. We have an interest in laser-induced damage and contamination from the long pulse only (~1ns), short pulse only (500fs) and combined regimes. For most of the operations the CPA system has operated at a wavelength of 1053nm (1ω). Some experiments have also been conducted with 527nm (2ω) CPA light derived by the use of a KDP doubling crystal. Damage to the infra red pulse compression gratings has occurred infrequently with a minority of high-energy shots. Contamination of multilayer dielectric plane turning mirrors has arisen from target disassembly. Focussing systems using off axis parabolic mirrors have sustained contamination from debris and a dielectric protected silver reflector used for green light suffered laser induced damage. Debris shields placed between the target and the parabolas have been used on selected experiments. The shields were anti-reflection coated with single layer, sol gel silica. These shields became contaminated on the target facing sides and in the case of 2ω operation also from blow off of the damaged mirror coating that caused a two-pass transmission loss in the system. A number of characterisation methods were used to evaluate and quantify the damage and contamination. These include macroscopic photography, microscopy, reflectometry and transmission spectroscopy.","PeriodicalId":204978,"journal":{"name":"SPIE Laser Damage","volume":"11 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132171770","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}
A critical component for the OMEGA EP short-pulse petawatt laser system is the grating compressor chamber (GCC). This large (12,375 ft3) vacuum chamber contains critical optics where laser-pulse compression is performed at the output of the system on two 40-cm-sq-aperture, IR (1054-nm) laser beams. Critical to this compression, within the GCC, are four sets of tiled multilayer-dielectric- (MLD) diffraction gratings that provide the capability for producing 2.6-kJ output IR energy per beam at 10 ps. The primary requirements for these large-aperture (43-cm × 47-cm) gratings are diffraction efficiencies greater than 95%, peak-to-valley wavefront quality of less than λ/10 waves, and laser-induced-damage thresholds greater than 2.7 J/cm2 at 10-ps measured beam normal. Degradation of the grating laser-damage threshold due to adsorption of contaminants from the manufacturing process must be prevented to maintain system performance. In this paper we discuss an optimized cleaning process to achieve the OMEGA EP requirements. The fabrication of MLD gratings involves processes that utilize a wide variety of both organic materials (photoresist processes) and inorganic materials (metals and metal oxides) that can affect the final cleaning process. A number of these materials have significant optical absorbance; therefore, incomplete cleaning of these residues may result in the MLD gratings experiencing laser damage.
{"title":"Optimizing a cleaning process for multilayer-dielectric- (MLD) diffraction gratings","authors":"B. Ashe, C. Giacofei, G. Myhre, A. Schmid","doi":"10.1117/12.751750","DOIUrl":"https://doi.org/10.1117/12.751750","url":null,"abstract":"A critical component for the OMEGA EP short-pulse petawatt laser system is the grating compressor chamber (GCC). This large (12,375 ft3) vacuum chamber contains critical optics where laser-pulse compression is performed at the output of the system on two 40-cm-sq-aperture, IR (1054-nm) laser beams. Critical to this compression, within the GCC, are four sets of tiled multilayer-dielectric- (MLD) diffraction gratings that provide the capability for producing 2.6-kJ output IR energy per beam at 10 ps. The primary requirements for these large-aperture (43-cm × 47-cm) gratings are diffraction efficiencies greater than 95%, peak-to-valley wavefront quality of less than λ/10 waves, and laser-induced-damage thresholds greater than 2.7 J/cm2 at 10-ps measured beam normal. Degradation of the grating laser-damage threshold due to adsorption of contaminants from the manufacturing process must be prevented to maintain system performance. In this paper we discuss an optimized cleaning process to achieve the OMEGA EP requirements. The fabrication of MLD gratings involves processes that utilize a wide variety of both organic materials (photoresist processes) and inorganic materials (metals and metal oxides) that can affect the final cleaning process. A number of these materials have significant optical absorbance; therefore, incomplete cleaning of these residues may result in the MLD gratings experiencing laser damage.","PeriodicalId":204978,"journal":{"name":"SPIE Laser Damage","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130022289","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}
L. Gallais, J. Capoulade, J. Natoli, M. Commandré, M. Cathelinaud, Cian Koc, M. Lequime
A comparative study is made on the laser damage resistance of monolayers coatings made with different technologies. HfO2 and SiO2 thin films have been deposited on fused silica substrates with Dual Ion Beam Sputtering, Electron Beam Deposition (with and without Ion Assistance) and Reactive Low Voltage Ion Plating technologies. The laser damage thresholds of these coatings have been determined at 1064nm and 355nm using a nanosecond pulsed YAG laser, and a 1-on-1 test procedure.
{"title":"Laser damage of silica and hafnia thin films made with different deposition technologies","authors":"L. Gallais, J. Capoulade, J. Natoli, M. Commandré, M. Cathelinaud, Cian Koc, M. Lequime","doi":"10.1117/12.752952","DOIUrl":"https://doi.org/10.1117/12.752952","url":null,"abstract":"A comparative study is made on the laser damage resistance of monolayers coatings made with different technologies. HfO2 and SiO2 thin films have been deposited on fused silica substrates with Dual Ion Beam Sputtering, Electron Beam Deposition (with and without Ion Assistance) and Reactive Low Voltage Ion Plating technologies. The laser damage thresholds of these coatings have been determined at 1064nm and 355nm using a nanosecond pulsed YAG laser, and a 1-on-1 test procedure.","PeriodicalId":204978,"journal":{"name":"SPIE Laser Damage","volume":"46 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124253785","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}
H. Schröder, S. Becker, Y. Lien, W. Riede, D. Wernham
In this paper, we present the continued joint effort of ESA/ESTEC and DLR laser laboratories of improving the fluorescence monitoring technique towards a quantitative means for analysis of UV laser-induced deposit formation on optical samples in vacuum. In addition, a separate low power UV fluorescence excitation light source was implemented into the system allowing the investigation of laser-induced deposition occurring during irradiation of optics with IR and VIS light beams.
{"title":"Fluorescence monitoring of organic deposits","authors":"H. Schröder, S. Becker, Y. Lien, W. Riede, D. Wernham","doi":"10.1117/12.752866","DOIUrl":"https://doi.org/10.1117/12.752866","url":null,"abstract":"In this paper, we present the continued joint effort of ESA/ESTEC and DLR laser laboratories of improving the fluorescence monitoring technique towards a quantitative means for analysis of UV laser-induced deposit formation on optical samples in vacuum. In addition, a separate low power UV fluorescence excitation light source was implemented into the system allowing the investigation of laser-induced deposition occurring during irradiation of optics with IR and VIS light beams.","PeriodicalId":204978,"journal":{"name":"SPIE Laser Damage","volume":"84 3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121220666","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. Agranat, S. Anisimov, S. Ashitkov, V. Zhakhovskiĭ, N. Inogamov, K. Nishihara, Y. Petrov
In the present work phenomena are considered related to the interaction of ultra-short laser pulses, τL~0.1 ps, with metallic targets. The absorption of laser pulse results in formation of thin layer of hot electrons strongly superheated (Te>>Ti) relative to the ion temperature, Ti. Initial thickness of the layer dheat is small, dheat~δ, where δ~10 nm is the skin layer thickness. Subsequent developments include the following stages: (1) Propagation of electron thermal wave which expands the hot layer dheat; (2) Cooling of electrons due to energy transfer to cold ions; (3) Onset of hydrodynamic motion that constitutes the rarefaction wave with positive pressure; (4) Further expansion of target material leading to the appearance of negative pressure; and (5) Long separation process which begins with nucleation of voids and goes on to the total separation of spallation plate. The thickness of the plate is ~10 nm (we call it nanospallation). Theoretical model involves two-temperature hydrodynamic equations with semiempirical EOS for a metal, electron heat conduction and electron-ion energy exchange. The decay of metastable strongly stretched matter is described by molecular dynamics (MD) simulation with extremely large number of atoms. The experimental setup includes femtosecond chromium-forsterite laser operating in the pump-probe regime. The experiments are performed with gold target. Measured ablation threshold for gold is 1.35 J/cm2 of incident pump light at inclination 45°, p-polarization. Calorimeter measurements give for the absorbed fluence Fabs=0.3Finc, therefore the threshold value of Fabs is 0.4 J/cm2.
{"title":"Nanospallation induced by a femtosecond laser pulse","authors":"M. Agranat, S. Anisimov, S. Ashitkov, V. Zhakhovskiĭ, N. Inogamov, K. Nishihara, Y. Petrov","doi":"10.1117/12.738550","DOIUrl":"https://doi.org/10.1117/12.738550","url":null,"abstract":"In the present work phenomena are considered related to the interaction of ultra-short laser pulses, τL~0.1 ps, with metallic targets. The absorption of laser pulse results in formation of thin layer of hot electrons strongly superheated (Te>>Ti) relative to the ion temperature, Ti. Initial thickness of the layer dheat is small, dheat~δ, where δ~10 nm is the skin layer thickness. Subsequent developments include the following stages: (1) Propagation of electron thermal wave which expands the hot layer dheat; (2) Cooling of electrons due to energy transfer to cold ions; (3) Onset of hydrodynamic motion that constitutes the rarefaction wave with positive pressure; (4) Further expansion of target material leading to the appearance of negative pressure; and (5) Long separation process which begins with nucleation of voids and goes on to the total separation of spallation plate. The thickness of the plate is ~10 nm (we call it nanospallation). Theoretical model involves two-temperature hydrodynamic equations with semiempirical EOS for a metal, electron heat conduction and electron-ion energy exchange. The decay of metastable strongly stretched matter is described by molecular dynamics (MD) simulation with extremely large number of atoms. The experimental setup includes femtosecond chromium-forsterite laser operating in the pump-probe regime. The experiments are performed with gold target. Measured ablation threshold for gold is 1.35 J/cm2 of incident pump light at inclination 45°, p-polarization. Calorimeter measurements give for the absorbed fluence Fabs=0.3Finc, therefore the threshold value of Fabs is 0.4 J/cm2.","PeriodicalId":204978,"journal":{"name":"SPIE Laser Damage","volume":"25 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128289387","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}
D. Nguyen, I. Cravetchi, L. Emmert, W. Rudolph, M. Jupé, M. Lappschies, K. Starke, D. Ristau
The scaling law of subpicosecond laser induced damage (LID) with respect to pulse duration and band gap for TixSi1-xO2 composite films is studied. The band gap in these materials can be changed gradually by varying the composition pa-rameter x. Damage is very deterministic and scaling laws with respect to pulse duration and band gap energy derived previously for pure materials are found to apply to composite films. The scaling can be explained theoretically by using a modified Keldysh theory. The composite materials also show a dependence of the damage threshold as a function of pulse number F(N) (incubation) that is similar to observations in pure dielectric oxides. The measured F(N) is explained with a theoretical model that assumes the formation of an intermediate sample state that increases the absorption of sub-sequent pulses in the train.
{"title":"Experimental and theoretical studies of subpicosecond laser damage in TixSi1-xO2 composite films","authors":"D. Nguyen, I. Cravetchi, L. Emmert, W. Rudolph, M. Jupé, M. Lappschies, K. Starke, D. Ristau","doi":"10.1117/12.753547","DOIUrl":"https://doi.org/10.1117/12.753547","url":null,"abstract":"The scaling law of subpicosecond laser induced damage (LID) with respect to pulse duration and band gap for TixSi1-xO2 composite films is studied. The band gap in these materials can be changed gradually by varying the composition pa-rameter x. Damage is very deterministic and scaling laws with respect to pulse duration and band gap energy derived previously for pure materials are found to apply to composite films. The scaling can be explained theoretically by using a modified Keldysh theory. The composite materials also show a dependence of the damage threshold as a function of pulse number F(N) (incubation) that is similar to observations in pure dielectric oxides. The measured F(N) is explained with a theoretical model that assumes the formation of an intermediate sample state that increases the absorption of sub-sequent pulses in the train.","PeriodicalId":204978,"journal":{"name":"SPIE Laser Damage","volume":"56 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115859370","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}
This work describes a homogeneous single layer model for surface roughness by polarized light. It has been shown that the reflectance change in non-absorbing layer is directly proportional to the refractive index of the ambient and substrate media for s polarization but inversely proportional to the p polarization and it is directly proportional to the square of the thickness of the layer for both the polarization. The thickness of the film has been written in terms of surface roughness to correlate the homogeneous model with the scattering theory. The consequence of the scattered light on the specular reflectance and transmittance for oblique incidence shows that there is reduction in reflectance and transmittance, due to roughness on the surface under the Drude effective-medium approximation.
{"title":"Effect of S and P polarization on single layer homogeneous model","authors":"Udaibir Singh, A. Kapoor","doi":"10.1117/12.752026","DOIUrl":"https://doi.org/10.1117/12.752026","url":null,"abstract":"This work describes a homogeneous single layer model for surface roughness by polarized light. It has been shown that the reflectance change in non-absorbing layer is directly proportional to the refractive index of the ambient and substrate media for s polarization but inversely proportional to the p polarization and it is directly proportional to the square of the thickness of the layer for both the polarization. The thickness of the film has been written in terms of surface roughness to correlate the homogeneous model with the scattering theory. The consequence of the scattered light on the specular reflectance and transmittance for oblique incidence shows that there is reduction in reflectance and transmittance, due to roughness on the surface under the Drude effective-medium approximation.","PeriodicalId":204978,"journal":{"name":"SPIE Laser Damage","volume":"86 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116459612","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}
We examine the effect of lattice temperature on the probability of surface damage initiation for 355nm, 7ns laser pulses for surface temperatures below the melting point to temperatures well above the melting point of fused silica. At sufficiently high surface temperatures, damage thresholds are dramatically reduced. Our results indicate a temperature activated absorption and support the idea of a lattice temperature threshold of surface damage. From these measurements, we estimate the temperature dependent absorption coefficient for intrinsic silica.
{"title":"The effect of lattice temperature on surface damage in fused silica optics","authors":"J. Bude, G. Guss, M. Matthews, M. Spaeth","doi":"10.1117/12.752989","DOIUrl":"https://doi.org/10.1117/12.752989","url":null,"abstract":"We examine the effect of lattice temperature on the probability of surface damage initiation for 355nm, 7ns laser pulses for surface temperatures below the melting point to temperatures well above the melting point of fused silica. At sufficiently high surface temperatures, damage thresholds are dramatically reduced. Our results indicate a temperature activated absorption and support the idea of a lattice temperature threshold of surface damage. From these measurements, we estimate the temperature dependent absorption coefficient for intrinsic silica.","PeriodicalId":204978,"journal":{"name":"SPIE Laser Damage","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130538392","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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