M. Matthews, I. Bass, G. Guss, C. Widmayer, F. Ravizza
Mitigation of 351nm laser-induced damage sites on fused silica exit surfaces by selective CO2 treatment has been shown to effectively arrest the exponential growth responsible for limiting the lifetime of optics in high-fluence laser systems. However, the perturbation to the optical surface profile following the mitigation process introduces phase contrast to the beam, causing some amount of downstream intensification with the potential to damage downstream optics. Control of the laser treatment process and measurement of the associated phase modulation is essential to preventing downstream 'fratricide' in damage-mitigated optical systems. In this work we present measurements of the surface morphology, intensification patterns and damage associated with various CO2 mitigation treatments on fused silica surfaces. Specifically, two components of intensification pattern, one on-axis and another off-axis can lead to damage of downstream optics and are related to rims around the ablation pit left from the mitigation process. It is shown that control of the rim structure around the edge of typical mitigation sites is crucial in preventing damage to downstream optics.
{"title":"Downstream intensification effects associated with CO2 laser mitigation of fused silica","authors":"M. Matthews, I. Bass, G. Guss, C. Widmayer, F. Ravizza","doi":"10.1117/12.752948","DOIUrl":"https://doi.org/10.1117/12.752948","url":null,"abstract":"Mitigation of 351nm laser-induced damage sites on fused silica exit surfaces by selective CO2 treatment has been shown to effectively arrest the exponential growth responsible for limiting the lifetime of optics in high-fluence laser systems. However, the perturbation to the optical surface profile following the mitigation process introduces phase contrast to the beam, causing some amount of downstream intensification with the potential to damage downstream optics. Control of the laser treatment process and measurement of the associated phase modulation is essential to preventing downstream 'fratricide' in damage-mitigated optical systems. In this work we present measurements of the surface morphology, intensification patterns and damage associated with various CO2 mitigation treatments on fused silica surfaces. Specifically, two components of intensification pattern, one on-axis and another off-axis can lead to damage of downstream optics and are related to rims around the ablation pit left from the mitigation process. It is shown that control of the rim structure around the edge of typical mitigation sites is crucial in preventing damage to downstream optics.","PeriodicalId":204978,"journal":{"name":"SPIE Laser Damage","volume":"416 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133584715","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. Feit, P. Demange, R. Negres, A. Rubenchik, S. Demos
Currently, most of our thinking about the defects responsible for initiating laser damage considers them as featureless absorbers. However, an increasing body of evidence, particularly involving multi-wavelength irradiation, suggests electronic structure of damage initiators is important in determining both initiation and conditioning behaviors in KDP. The effective absorption coefficient of energy under multi-wavelength irradiation cannot be accounted for by a structureless absorber, but is consistent with an initiator with a multi-level structure. We outline the evidence and assess the ability of such a simple multi-level model to explain these and other experimentally observed behaviors.
{"title":"Does complex absorption behavior leading to conditioning and damage in KDP/DKDP reflect the electronic structure of initiators?","authors":"M. Feit, P. Demange, R. Negres, A. Rubenchik, S. Demos","doi":"10.1117/12.748444","DOIUrl":"https://doi.org/10.1117/12.748444","url":null,"abstract":"Currently, most of our thinking about the defects responsible for initiating laser damage considers them as featureless absorbers. However, an increasing body of evidence, particularly involving multi-wavelength irradiation, suggests electronic structure of damage initiators is important in determining both initiation and conditioning behaviors in KDP. The effective absorption coefficient of energy under multi-wavelength irradiation cannot be accounted for by a structureless absorber, but is consistent with an initiator with a multi-level structure. We outline the evidence and assess the ability of such a simple multi-level model to explain these and other experimentally observed behaviors.","PeriodicalId":204978,"journal":{"name":"SPIE Laser Damage","volume":"200 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122532635","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}
Laser-induced breakdown in the bulk of transparent dielectric materials is associated with the generation of extreme localized conditions of temperatures and pressures. In this work, we perform pump and probe damage testing experiments to investigate the evolution of transient absorption by the host material arising from modifications following confined laser energy deposition in fused silica and DKDP materials. Specifically, we measure the size of the damage sites observed in the region of spatial overlap between the pump and probe pulses versus probe time delay and energy. Results of this proof-of-principle experimental work confirm that material modifications under extreme conditions created during a damage event include transient optical absorption. In addition, we found that the relaxation times of the induced absorption are very distinct for DKDP and SiO2 even under identical excitation conditions, on the order of 100 ns and 100 μs, respectively.
{"title":"Pump and probe damage testing for investigation of transient material modifications associated with laser damage in optical materials","authors":"R. Negres, M. Feit, P. Demange, J. Bude, S. Demos","doi":"10.1117/12.750091","DOIUrl":"https://doi.org/10.1117/12.750091","url":null,"abstract":"Laser-induced breakdown in the bulk of transparent dielectric materials is associated with the generation of extreme localized conditions of temperatures and pressures. In this work, we perform pump and probe damage testing experiments to investigate the evolution of transient absorption by the host material arising from modifications following confined laser energy deposition in fused silica and DKDP materials. Specifically, we measure the size of the damage sites observed in the region of spatial overlap between the pump and probe pulses versus probe time delay and energy. Results of this proof-of-principle experimental work confirm that material modifications under extreme conditions created during a damage event include transient optical absorption. In addition, we found that the relaxation times of the induced absorption are very distinct for DKDP and SiO2 even under identical excitation conditions, on the order of 100 ns and 100 μs, respectively.","PeriodicalId":204978,"journal":{"name":"SPIE Laser Damage","volume":"71 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126251426","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. Hildenbrand, F. Wagner, H. Akhouayri, J. Natoli, M. Commandré
Laser damage measurements in nonlinear optical crystals, in particular in biaxial crystals, may be influenced by several effects proper to these materials or greatly enhanced in these materials. Before discussion of these effects, we address the topic of error bar determination for probability measurements. Error bars for the damage probabilities are important because nonlinear crystals are often small and expensive, thus only few sites are used for a single damage probability measurement. We present the mathematical basics and a flow diagram for the numerical calculation of error bars for probability measurements that correspond to a chosen confidence level. Effects that possibly modify the maximum intensity in a biaxial nonlinear crystal are: focusing aberration, walk-off and self-focusing. Depending on focusing conditions, propagation direction, polarization of the light and the position of the focus point in the crystal, strong aberrations may change the beam profile and drastically decrease the maximum intensity in the crystal. A correction factor for this effect is proposed, but quantitative corrections are not possible without taking into account the experimental beam profile after the focusing lens. The characteristics of walk-off and self-focusing have quickly been reviewed for the sake of completeness of this article. Finally, parasitic second harmonic generation may influence the laser damage behavior of crystals. The important point for laser damage measurements is that the amount of externally observed SHG after the crystal does not correspond to the maximum amount of second harmonic light inside the crystal.
{"title":"Laser damage metrology in biaxial nonlinear crystals using different test beams","authors":"A. Hildenbrand, F. Wagner, H. Akhouayri, J. Natoli, M. Commandré","doi":"10.1117/12.752918","DOIUrl":"https://doi.org/10.1117/12.752918","url":null,"abstract":"Laser damage measurements in nonlinear optical crystals, in particular in biaxial crystals, may be influenced by several effects proper to these materials or greatly enhanced in these materials. Before discussion of these effects, we address the topic of error bar determination for probability measurements. Error bars for the damage probabilities are important because nonlinear crystals are often small and expensive, thus only few sites are used for a single damage probability measurement. We present the mathematical basics and a flow diagram for the numerical calculation of error bars for probability measurements that correspond to a chosen confidence level. Effects that possibly modify the maximum intensity in a biaxial nonlinear crystal are: focusing aberration, walk-off and self-focusing. Depending on focusing conditions, propagation direction, polarization of the light and the position of the focus point in the crystal, strong aberrations may change the beam profile and drastically decrease the maximum intensity in the crystal. A correction factor for this effect is proposed, but quantitative corrections are not possible without taking into account the experimental beam profile after the focusing lens. The characteristics of walk-off and self-focusing have quickly been reviewed for the sake of completeness of this article. Finally, parasitic second harmonic generation may influence the laser damage behavior of crystals. The important point for laser damage measurements is that the amount of externally observed SHG after the crystal does not correspond to the maximum amount of second harmonic light inside the crystal.","PeriodicalId":204978,"journal":{"name":"SPIE Laser Damage","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123710258","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}
Surface and coating technology plays an important role for extending lifetime of fluoride optics for ArF excimer laser applications. Optically finished CaF2 optics is characterized as top surface and subsurface by means of non-distractive quasi-Brewster angle technique. The subsurface is revealed by removing the top surface via distractive methods. Color centers on plasma ion and laser irradiated CaF2 optics are discussed. The results suggest that fluorine depletion is associated with laser damage, dense smooth coatings enable one to extend the lifetime of CaF2 optics.
{"title":"Extended lifetime of fluoride optics","authors":"Jue Wang, C. Clar, H. Schreiber","doi":"10.1117/12.753045","DOIUrl":"https://doi.org/10.1117/12.753045","url":null,"abstract":"Surface and coating technology plays an important role for extending lifetime of fluoride optics for ArF excimer laser applications. Optically finished CaF2 optics is characterized as top surface and subsurface by means of non-distractive quasi-Brewster angle technique. The subsurface is revealed by removing the top surface via distractive methods. Color centers on plasma ion and laser irradiated CaF2 optics are discussed. The results suggest that fluorine depletion is associated with laser damage, dense smooth coatings enable one to extend the lifetime of CaF2 optics.","PeriodicalId":204978,"journal":{"name":"SPIE Laser Damage","volume":"13 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122882761","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. Qi, Kui Yi, Hua Yu, Yun Cui, Da-wei Li, Zhixing Gao, J. Shao, Z. Fan
In order to study the effect of material properties on the laser induced damage of dielectric coatings at a wavelength of 248 nm, multilayer coatings were deposited by electron beam reactive evaporation technique onto fused silica substrates with the materials of hafnium oxide, aluminum oxide and silicon dioxide. Laser-induced damage thresholds (LIDTs), morphologies and profiles of damage sites of multilayer thin films were measured to investigate the damage mechanism. Besides, with our programmed software, the temperature rise in the multilayers was calculated to better understand the relationship between damage morphology, electric field peak location and depth of damage sites. The results indicate that the absorption of defect and the electric field distribution of thin film greatly contribute to LIDTs of thin films, and the control of defect, especially defect with strong absorption, is still the only way to improve the laser radiation resistivity of coatings in the UV spectral region.
{"title":"Laser-induced damage of multilayer high-reflectance coatings for 248 nm","authors":"H. Qi, Kui Yi, Hua Yu, Yun Cui, Da-wei Li, Zhixing Gao, J. Shao, Z. Fan","doi":"10.1117/12.752803","DOIUrl":"https://doi.org/10.1117/12.752803","url":null,"abstract":"In order to study the effect of material properties on the laser induced damage of dielectric coatings at a wavelength of 248 nm, multilayer coatings were deposited by electron beam reactive evaporation technique onto fused silica substrates with the materials of hafnium oxide, aluminum oxide and silicon dioxide. Laser-induced damage thresholds (LIDTs), morphologies and profiles of damage sites of multilayer thin films were measured to investigate the damage mechanism. Besides, with our programmed software, the temperature rise in the multilayers was calculated to better understand the relationship between damage morphology, electric field peak location and depth of damage sites. The results indicate that the absorption of defect and the electric field distribution of thin film greatly contribute to LIDTs of thin films, and the control of defect, especially defect with strong absorption, is still the only way to improve the laser radiation resistivity of coatings in the UV spectral region.","PeriodicalId":204978,"journal":{"name":"SPIE Laser Damage","volume":"60 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116261773","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}
In the field of optical communication, either fusion splicing of optical fibers or physical contact between optical-fibers using a fiber connector has been utilized as the typical method of optical fiber connection. Optical fiber connectors have been widely employed in optical transmission systems according to their features of easy and quick connection without special apparatus to connect fibers. The power of laser diodes for light sources became more intense and the multiplexing of wavelength (WDM) of a light source was enhanced with increasing traffic data. As a result, intense light transmits through the optical fiber. The high power transmission characteristics of the optical fiber connector are important factors to realize dense wavelength division multiplexing systems (DWDM). In this paper, we present an experimental investigation about the degradation of the transmission properties through the optical fiber connector by introducing the contamination between the end faces of a connector. The metal foils to simulate the contamination at the end of the core were inserted between the optical fibers to cover the core of an optical fiber partially. As metal foils, Nickel, SUS304, and Phosphor Bronze which were typically used as the components of the ferrule and sleeve were selected. The Nd: YAG laser with the wavelength of 1064 nm was used as a high power light source at various output powers. The transmission loss was set by adjusting the insertion of a metal foil into the core region of the fiber and the temperature rising of the connector induced by the absorption of incident light was measured at a sleeve portion. The damage at the end face of the physical contact region was observed using an optical microscope. The temperatures increase of the core of the fiber was estimated for the fiber connector with a zirconia ferrule through the thermal simulation using the MSC Visual Nastran. The damage of the fiber end face was recognized depending on the species of the metal foil and the covering ratio for the core in the case of a high power light transmission, typically, with the average power of 1W. It was estimated that the damage threshold of the fiber end becomes low for the ferrule with lower melting point. The correlation between the damage threshold and various parameters was discussed.
{"title":"Damage characteristics at optical fiber connector for high power light transmission","authors":"S. Matsuda, T. Shibuya, M. Wakaki","doi":"10.1117/12.752817","DOIUrl":"https://doi.org/10.1117/12.752817","url":null,"abstract":"In the field of optical communication, either fusion splicing of optical fibers or physical contact between optical-fibers using a fiber connector has been utilized as the typical method of optical fiber connection. Optical fiber connectors have been widely employed in optical transmission systems according to their features of easy and quick connection without special apparatus to connect fibers. The power of laser diodes for light sources became more intense and the multiplexing of wavelength (WDM) of a light source was enhanced with increasing traffic data. As a result, intense light transmits through the optical fiber. The high power transmission characteristics of the optical fiber connector are important factors to realize dense wavelength division multiplexing systems (DWDM). In this paper, we present an experimental investigation about the degradation of the transmission properties through the optical fiber connector by introducing the contamination between the end faces of a connector. The metal foils to simulate the contamination at the end of the core were inserted between the optical fibers to cover the core of an optical fiber partially. As metal foils, Nickel, SUS304, and Phosphor Bronze which were typically used as the components of the ferrule and sleeve were selected. The Nd: YAG laser with the wavelength of 1064 nm was used as a high power light source at various output powers. The transmission loss was set by adjusting the insertion of a metal foil into the core region of the fiber and the temperature rising of the connector induced by the absorption of incident light was measured at a sleeve portion. The damage at the end face of the physical contact region was observed using an optical microscope. The temperatures increase of the core of the fiber was estimated for the fiber connector with a zirconia ferrule through the thermal simulation using the MSC Visual Nastran. The damage of the fiber end face was recognized depending on the species of the metal foil and the covering ratio for the core in the case of a high power light transmission, typically, with the average power of 1W. It was estimated that the damage threshold of the fiber end becomes low for the ferrule with lower melting point. The correlation between the damage threshold and various parameters was discussed.","PeriodicalId":204978,"journal":{"name":"SPIE Laser Damage","volume":"58 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132201402","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}
K. Mann, A. Bayer, T. Miege, U. Leinhos, B. Schäfer
For an assessment of the optical quality of DUV optics, a high-sensitivity wavefront analyzer system based on the Hartmann-Shack principle is employed. The device accomplishes precise on-line monitoring of wavefront deformations of a collimated test beam transmitted through the laser-irradiated site of a sample. Due to the achieved sub-nm resolution, it can be used as an alternative to calorimetric and interferometric measurements for 'at wavelength' testing of optics, e.g. for on-line registration of thermal lensing effects or compaction in fused silica. By recording wavefront distortions of fused silica samples of different thickness and at different fluences the contribution of bulk and surface to the total absorption as well as one- and two-photon effects can be separated.
{"title":"A novel photo-thermal setup for evaluation of absorptance losses and thermal wavefront deformations in DUV optics","authors":"K. Mann, A. Bayer, T. Miege, U. Leinhos, B. Schäfer","doi":"10.1117/12.776945","DOIUrl":"https://doi.org/10.1117/12.776945","url":null,"abstract":"For an assessment of the optical quality of DUV optics, a high-sensitivity wavefront analyzer system based on the Hartmann-Shack principle is employed. The device accomplishes precise on-line monitoring of wavefront deformations of a collimated test beam transmitted through the laser-irradiated site of a sample. Due to the achieved sub-nm resolution, it can be used as an alternative to calorimetric and interferometric measurements for 'at wavelength' testing of optics, e.g. for on-line registration of thermal lensing effects or compaction in fused silica. By recording wavefront distortions of fused silica samples of different thickness and at different fluences the contribution of bulk and surface to the total absorption as well as one- and two-photon effects can be separated.","PeriodicalId":204978,"journal":{"name":"SPIE Laser Damage","volume":"43 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125366323","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 utilization of oxide mixtures as layer material for coating design has been transferred to the ion beam sputtering technology and was applied to high-reflecting as well as anti-reflecting components at the wavelength of 193nm. Exclusively, the oxides SiO2 and Al2O3 are candidates for appropriate thin film designs below 200nm. Experimental data received from laser-calorimetric measurements, spectroscopic investigations and laser-induced damage tests are presented for several specimens. With respect to state-of-the-art thin film deposition in the DUV spectral range, conventional quarterwave designs have also been characterized and will be compared to the sputtered mixed oxide coatings.
{"title":"Performance enhancement of ion beam sputtered oxide coatings for 193 nm","authors":"H. Blaschke, M. Lappschies, D. Ristau","doi":"10.1117/12.752908","DOIUrl":"https://doi.org/10.1117/12.752908","url":null,"abstract":"The utilization of oxide mixtures as layer material for coating design has been transferred to the ion beam sputtering technology and was applied to high-reflecting as well as anti-reflecting components at the wavelength of 193nm. Exclusively, the oxides SiO2 and Al2O3 are candidates for appropriate thin film designs below 200nm. Experimental data received from laser-calorimetric measurements, spectroscopic investigations and laser-induced damage tests are presented for several specimens. With respect to state-of-the-art thin film deposition in the DUV spectral range, conventional quarterwave designs have also been characterized and will be compared to the sputtered mixed oxide coatings.","PeriodicalId":204978,"journal":{"name":"SPIE Laser Damage","volume":"53 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122398857","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 artificially grown calcium fluoride is used as materials of the optics such as the lenses of the illumination optical system and the projection optical system of the lithography equipment that use the sources of light such as excimer lasers. Such calcium fluoride is required high transmittance. However, there are very small scatterers and absorbers inside the crystal and they cause degradation of transmittance. In this study, we examined these defects and clarified the process how they occur. Haze is characteristic optical defect in the artificially grown calcium fluoride. It is thought that haze is an aggregation of very small scatterers and this scatterer is void or calcium oxide crystal. When we irradiate the light into a crystal with much haze, the path of the light looks white. However, we were not able to clarify neither the structure nor components of haze. First, we examined how the scatterers were distributed by an infrared tomography method. The result pointed out that the scatterers were located along sub-grain boundary and dislocation network. We prepared a surface sample for TEM (Transmission Electron Microscopy) with FIB (Focused Ion Beam) from the point where it seemed that the scatterers were located in the dislocation network, and observed it with TEM and analyzed grain boundary region and the grain inside with EDS (Energy Dispersive X-ray Spectroscopy). From the EDS spectrum of the grain boundary region, a very small amount of oxygen was detected, but no oxygen was detected from the grain inside. This suggests that oxygen is located in the grain boundary. From these results, it is suggested that scatterers of haze are made of oxygen voids or calcium oxides crystals.
{"title":"Study of haze in artificially grown single crystal CaF2","authors":"M. Azumi","doi":"10.1117/12.760768","DOIUrl":"https://doi.org/10.1117/12.760768","url":null,"abstract":"The artificially grown calcium fluoride is used as materials of the optics such as the lenses of the illumination optical system and the projection optical system of the lithography equipment that use the sources of light such as excimer lasers. Such calcium fluoride is required high transmittance. However, there are very small scatterers and absorbers inside the crystal and they cause degradation of transmittance. In this study, we examined these defects and clarified the process how they occur. Haze is characteristic optical defect in the artificially grown calcium fluoride. It is thought that haze is an aggregation of very small scatterers and this scatterer is void or calcium oxide crystal. When we irradiate the light into a crystal with much haze, the path of the light looks white. However, we were not able to clarify neither the structure nor components of haze. First, we examined how the scatterers were distributed by an infrared tomography method. The result pointed out that the scatterers were located along sub-grain boundary and dislocation network. We prepared a surface sample for TEM (Transmission Electron Microscopy) with FIB (Focused Ion Beam) from the point where it seemed that the scatterers were located in the dislocation network, and observed it with TEM and analyzed grain boundary region and the grain inside with EDS (Energy Dispersive X-ray Spectroscopy). From the EDS spectrum of the grain boundary region, a very small amount of oxygen was detected, but no oxygen was detected from the grain inside. This suggests that oxygen is located in the grain boundary. From these results, it is suggested that scatterers of haze are made of oxygen voids or calcium oxides crystals.","PeriodicalId":204978,"journal":{"name":"SPIE Laser Damage","volume":"41 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125938086","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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