So far, laser calorimetry (LCA) as absorptance measurement procedure according to ISO 11551 has been commonly performed at a variety of selected laser wavelengths. Thus, this procedure has been a valuable tool for optimization processes of dielectric coatings. For an even more comprehensive detection of any absorbing contribution in a dielectric layer stack a free selectable test wavelength gives more detailed insights in optics characterization. According to this approach an OPO system was implemented in a laser calorimetric test bench. By this, a tunable laser source with sufficient laser power is available to conduct calorimetric absorptance measurements. Results of detailed investigations of the contribution of the material constituents of a dielectric optical component are presented in this paper.
{"title":"Spectrally resolved laser calorimetric absorptance measurements","authors":"L. Jensen, I. Balasa, K. Starke, D. Ristau","doi":"10.1117/12.752907","DOIUrl":"https://doi.org/10.1117/12.752907","url":null,"abstract":"So far, laser calorimetry (LCA) as absorptance measurement procedure according to ISO 11551 has been commonly performed at a variety of selected laser wavelengths. Thus, this procedure has been a valuable tool for optimization processes of dielectric coatings. For an even more comprehensive detection of any absorbing contribution in a dielectric layer stack a free selectable test wavelength gives more detailed insights in optics characterization. According to this approach an OPO system was implemented in a laser calorimetric test bench. By this, a tunable laser source with sufficient laser power is available to conduct calorimetric absorptance measurements. Results of detailed investigations of the contribution of the material constituents of a dielectric optical component are presented in this paper.","PeriodicalId":204978,"journal":{"name":"SPIE Laser Damage","volume":"35 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":"132964729","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. Surmin, S. Lambert, F. Guillet, B. Minot, D. Damiani, F. Gervais
In this paper, the nature of the crystalline phases observed at the surface damage sites resulting from laser irradiation is investigated by X-ray diffraction. The results are compared against new data on thermal decomposition of KDP salt. The damage sites consist of polycrystalline KDP and partially dehydrated phases. The comparison with the thermal decomposition study allows to assign a temperature range to the overall temperature reached by the surface during the damaging process. Finally, the difference between surface damage and bulk damage is discussed.
{"title":"Thermal mechanism of laser-induced damages in KDP crystals","authors":"A. Surmin, S. Lambert, F. Guillet, B. Minot, D. Damiani, F. Gervais","doi":"10.1117/12.752824","DOIUrl":"https://doi.org/10.1117/12.752824","url":null,"abstract":"In this paper, the nature of the crystalline phases observed at the surface damage sites resulting from laser irradiation is investigated by X-ray diffraction. The results are compared against new data on thermal decomposition of KDP salt. The damage sites consist of polycrystalline KDP and partially dehydrated phases. The comparison with the thermal decomposition study allows to assign a temperature range to the overall temperature reached by the surface during the damaging process. Finally, the difference between surface damage and bulk damage is discussed.","PeriodicalId":204978,"journal":{"name":"SPIE Laser Damage","volume":"2016 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":"127465396","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}
G. Abromavičius, R. Buzelis, R. Drazdys, A. Melninkaitis, V. Sirutkaitis
Various investigations show that damage threshold of optical coatings by intense ultrashort laser pulses is closely related to the intensity of electric field at layer interfaces. LIDT measurements of high reflectance optical coatings using femtosecond pulses at 800 nm wavelength are presented. ZrO2, HfO2 and Ta2O5 as high refractive index materials for two sets of experiments were chosen. Two different coating designs were investigated: standard quarter-wavelength design with SiO2 overcoat and modified "E-field" non quarter-wavelength design with suppressed electric field. Damage sites were studied using optical and AFM microscopes. Relation between electric field distribution and damage morphology was observed. The results demonstrate, that suppressing electric field at layer interfaces enables to increase LIDT for high reflectance coatings almost twice if compared to standard quarter-wavelength design when using ultrashort laser pulses. However electric field distribution is sensitive to variations in thicknesses of outer layers, so deposition process should be precisely controlled to get improvement in LIDT of coatings.
{"title":"Influence of electric field distribution on laser induced damage threshold and morphology of high reflectance optical coatings","authors":"G. Abromavičius, R. Buzelis, R. Drazdys, A. Melninkaitis, V. Sirutkaitis","doi":"10.1117/12.752902","DOIUrl":"https://doi.org/10.1117/12.752902","url":null,"abstract":"Various investigations show that damage threshold of optical coatings by intense ultrashort laser pulses is closely related to the intensity of electric field at layer interfaces. LIDT measurements of high reflectance optical coatings using femtosecond pulses at 800 nm wavelength are presented. ZrO2, HfO2 and Ta2O5 as high refractive index materials for two sets of experiments were chosen. Two different coating designs were investigated: standard quarter-wavelength design with SiO2 overcoat and modified \"E-field\" non quarter-wavelength design with suppressed electric field. Damage sites were studied using optical and AFM microscopes. Relation between electric field distribution and damage morphology was observed. The results demonstrate, that suppressing electric field at layer interfaces enables to increase LIDT for high reflectance coatings almost twice if compared to standard quarter-wavelength design when using ultrashort laser pulses. However electric field distribution is sensitive to variations in thicknesses of outer layers, so deposition process should be precisely controlled to get improvement in LIDT of coatings.","PeriodicalId":204978,"journal":{"name":"SPIE Laser Damage","volume":"32 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":"129982718","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 resistance of large optical components remains an important limitation for the performances and the maintenance costs in LMJ or NIF projects. For practical reasons LIDT studies are commonly performed with small samples and table top lasers whose characteristics change from one to another. In these conditions, it is necessary to know exactly the influence of the different experimental parameters (wavelength, spot size, ...) on the final data. These considerations are particularly true in heterogeneous materials as KDP crystals. Indeed the use of different laser beam sizes (from μm to hundreds μm) to plot laser damage probability curves had clearly shown that at 355nm in KDP, it is possible to exhibit a limit of irradiated area which permit to distinguish two different LIDT associated with two laser damage precursors densities. This prior result has put in evidence the influence of irradiated beam size in the discrimination of different kinds of defects in KDP. We present in this paper a systematic study of beam size effect in KDP for three different wavelengths: 355nm, 532nm and 1064nm. This study performed in 1:1 and R:1 mode will reveal precursors for each wavelength and their respective evolution under repetitive shots for small and large beams. This multi-parameters study will help us to highlight mechanisms involved in laser-induced damage in KDP crystal.
{"title":"Influence of laser beam size and wavelength in the determination of LIDT and associated laser damage precursor densities in KH2PO4","authors":"J. Natoli, J. Capoulade, H. Piombini, B. Bertussi","doi":"10.1117/12.750142","DOIUrl":"https://doi.org/10.1117/12.750142","url":null,"abstract":"The laser resistance of large optical components remains an important limitation for the performances and the maintenance costs in LMJ or NIF projects. For practical reasons LIDT studies are commonly performed with small samples and table top lasers whose characteristics change from one to another. In these conditions, it is necessary to know exactly the influence of the different experimental parameters (wavelength, spot size, ...) on the final data. These considerations are particularly true in heterogeneous materials as KDP crystals. Indeed the use of different laser beam sizes (from μm to hundreds μm) to plot laser damage probability curves had clearly shown that at 355nm in KDP, it is possible to exhibit a limit of irradiated area which permit to distinguish two different LIDT associated with two laser damage precursors densities. This prior result has put in evidence the influence of irradiated beam size in the discrimination of different kinds of defects in KDP. We present in this paper a systematic study of beam size effect in KDP for three different wavelengths: 355nm, 532nm and 1064nm. This study performed in 1:1 and R:1 mode will reveal precursors for each wavelength and their respective evolution under repetitive shots for small and large beams. This multi-parameters study will help us to highlight mechanisms involved in laser-induced damage in KDP crystal.","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":"114763837","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 James Webb Space Telescope (JWST) is a large space based astronomical telescope that will operate at cryogenic temperatures in an Earth-Sun L2 Orbit. The architecture has the telescope exposed to space, with a large sun shield providing thermal isolation and protection from direct illumination from the sun. The instruments will have the capability to observe over a spectral range from 0.6 μm to 28 μm wavelengths. The following paper will present an overview of the architecture and describe some of the features of the optical design for the JWST environment.
{"title":"James Webb Space Telescope: a large deployable cryogenic telescope in space","authors":"P. Lightsey","doi":"10.1117/12.754010","DOIUrl":"https://doi.org/10.1117/12.754010","url":null,"abstract":"The James Webb Space Telescope (JWST) is a large space based astronomical telescope that will operate at cryogenic temperatures in an Earth-Sun L2 Orbit. The architecture has the telescope exposed to space, with a large sun shield providing thermal isolation and protection from direct illumination from the sun. The instruments will have the capability to observe over a spectral range from 0.6 μm to 28 μm wavelengths. The following paper will present an overview of the architecture and describe some of the features of the optical design for the JWST environment.","PeriodicalId":204978,"journal":{"name":"SPIE Laser Damage","volume":"18 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":"125920926","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. Guillet, B. Bertussi, L. Lamaignère, X. Leborgne, B. Minot
As laser conditioning ever increases the performance of KDP optics with respect to laser induced bulk damage so that it can meet high-power laser specifications, it is expected that surface damage may become the next threat that must be dealt with. This paper presents new data on surface damage initiation and growth at 3w. A surface damage mitigation process based on the ball-dimpling method is presented along with the first results on the behavior of this process with respect to laser irradiation.
{"title":"Preliminary results on mitigation of KDP surface damage using the ball dimpling method","authors":"F. Guillet, B. Bertussi, L. Lamaignère, X. Leborgne, B. Minot","doi":"10.1117/12.752822","DOIUrl":"https://doi.org/10.1117/12.752822","url":null,"abstract":"As laser conditioning ever increases the performance of KDP optics with respect to laser induced bulk damage so that it can meet high-power laser specifications, it is expected that surface damage may become the next threat that must be dealt with. This paper presents new data on surface damage initiation and growth at 3w. A surface damage mitigation process based on the ball-dimpling method is presented along with the first results on the behavior of this process with respect to laser irradiation.","PeriodicalId":204978,"journal":{"name":"SPIE Laser Damage","volume":"36 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":"122155438","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. Lamaignère, S. Reyné, M. Loiseau, J. Poncetta, H. Bercegol
Campaigns of laser damage tests at 1w of Nd-YAG laser (1064 nm), 3w and with a combination of these two wavelengths, were conducted to complete previous existing data on damage growth in fused silica output surface. It is known that UV light is very effective in inducing preexisting damage craters to grow. When both wavelengths are present, the effect of 1w beam on damage growth depends on the delay between the IR and the UV beam. When the 1w reaches the sample before the 3w, it has nearly no consequence on growth rate. On the opposite, when the IR beam is delayed and strikes the sample after the 3w pulse, its energy simply adds to the UV in enhancing damage growth. Damage initiation is much more affected by 3w than 1w pulses. However, the number of surface damage craters also increased by the addition of 1w photons to the UV beam.
{"title":"Effects of wavelengths combination on initiation and growth of laser-induced surface damage in SiO2","authors":"L. Lamaignère, S. Reyné, M. Loiseau, J. Poncetta, H. Bercegol","doi":"10.1117/12.753057","DOIUrl":"https://doi.org/10.1117/12.753057","url":null,"abstract":"Campaigns of laser damage tests at 1w of Nd-YAG laser (1064 nm), 3w and with a combination of these two wavelengths, were conducted to complete previous existing data on damage growth in fused silica output surface. It is known that UV light is very effective in inducing preexisting damage craters to grow. When both wavelengths are present, the effect of 1w beam on damage growth depends on the delay between the IR and the UV beam. When the 1w reaches the sample before the 3w, it has nearly no consequence on growth rate. On the opposite, when the IR beam is delayed and strikes the sample after the 3w pulse, its energy simply adds to the UV in enhancing damage growth. Damage initiation is much more affected by 3w than 1w pulses. However, the number of surface damage craters also increased by the addition of 1w photons to the UV beam.","PeriodicalId":204978,"journal":{"name":"SPIE Laser Damage","volume":"50 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":"130666506","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}
G. Razé, J. Néauport, G. Dupuy, M. Balas, G. Mennerat, E. Lavastre
An optical bench was developed to measure laser induced damage thresholds in 1:1 and S:1 modes on mirror and grating samples. The laser based on Ti. Sapphire technology delivers Gaussian pulse of 500fs with a maximal energy of 3mJ at 1057nm. The experimental setup can deliver on the sample a peak fluence of 9J/cm2 in right section of the beam with a spot size of 200μm (diameter at 1/e2). Laser induced damage thresholds have been measured on several multidielectric samples produced with different processes. We present in this paper the damage testing setup in details and give some of the obtained results.
{"title":"Short pulse laser damage measurements of pulse compression gratings for petawatt laser","authors":"G. Razé, J. Néauport, G. Dupuy, M. Balas, G. Mennerat, E. Lavastre","doi":"10.1117/12.752783","DOIUrl":"https://doi.org/10.1117/12.752783","url":null,"abstract":"An optical bench was developed to measure laser induced damage thresholds in 1:1 and S:1 modes on mirror and grating samples. The laser based on Ti. Sapphire technology delivers Gaussian pulse of 500fs with a maximal energy of 3mJ at 1057nm. The experimental setup can deliver on the sample a peak fluence of 9J/cm2 in right section of the beam with a spot size of 200μm (diameter at 1/e2). Laser induced damage thresholds have been measured on several multidielectric samples produced with different processes. We present in this paper the damage testing setup in details and give some of the obtained results.","PeriodicalId":204978,"journal":{"name":"SPIE Laser Damage","volume":"27 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":"133094852","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}
Numerous experimental and theoretical contributions in the past have stressed the detrimental effect of fractures in the generation of surface laser damage sites in fused silica illuminated at 351 nm. However, two very important steps lack for the moment on the way towards a scientific understanding of the role of fractures. 1. a physical model must be developed to predict damage events starting from real defect sites 2. a reproducible measurement must be obtained and compared with calculations. Here we present the theoretical work realized to reach the first goal. Contrary to previous discussions on fractures, the electromagnetic configuration is calculated in the case of a real material, with electronic surface states, bulk defects, and defects dynamics. Due to electromagnetic field enhancement in the fracture, surface defects absorb a sufficient part of laser energy, able to heat silica above the vaporization temperature. This is the initial event that triggers production of more excited states during the pulse, and steep increase of temperature and pressure fields. Comparisons with available experimental results are positive. Calculated fluences of damage initiation are very near those of measured events on engineered fractures, or on real defects in polished samples.
{"title":"Progress in the understanding of fracture related laser damage of fused silica","authors":"H. Bercegol, P. Grua, D. Hébert, J. Morreeuw","doi":"10.1117/12.752830","DOIUrl":"https://doi.org/10.1117/12.752830","url":null,"abstract":"Numerous experimental and theoretical contributions in the past have stressed the detrimental effect of fractures in the generation of surface laser damage sites in fused silica illuminated at 351 nm. However, two very important steps lack for the moment on the way towards a scientific understanding of the role of fractures. 1. a physical model must be developed to predict damage events starting from real defect sites 2. a reproducible measurement must be obtained and compared with calculations. Here we present the theoretical work realized to reach the first goal. Contrary to previous discussions on fractures, the electromagnetic configuration is calculated in the case of a real material, with electronic surface states, bulk defects, and defects dynamics. Due to electromagnetic field enhancement in the fracture, surface defects absorb a sufficient part of laser energy, able to heat silica above the vaporization temperature. This is the initial event that triggers production of more excited states during the pulse, and steep increase of temperature and pressure fields. Comparisons with available experimental results are positive. Calculated fluences of damage initiation are very near those of measured events on engineered fractures, or on real defects in polished samples.","PeriodicalId":204978,"journal":{"name":"SPIE Laser Damage","volume":"1 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":"128560029","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 this paper we analyze the photo-excitation of electron sub-system of a periodic nano-structure by IR laser radiation. The nano-structure is a 1D super-lattice on surface of dielectric or semiconductor material transparent for the incident radiation. Theoretical description of the photo-excitation is based on the recent modification of the Keldysh theory adapted to the 1D case. We show that two specific regimes of the photo-excitation are possible in the super-lattices: photo-excitation suppression corresponding to decrease of the photo-excitation rate with increasing of laser intensity, and singularity regime corresponding to abrupt increase of the photo-ionization rate. Threshold of the singularity regime is calculated as function of laser wavelength and super-lattice period. The obtained results allow to propose a promising application of the super-lattices as intensity limiters for IR optical systems. In particular, we can calculate the period of the super-lattice to provide limiting of input laser intensity at required level due to multi-photon absorption by electrons of the lattice. Temperature of laser-induced heating resulted from total absorption of an incident laser pulse and diffraction distortions induced by the super-lattice are estimated to confirm possibility of utilizing the super-lattices as the intensity limiters.
{"title":"Photo-ionization of superlattices on dielectric surface by IR radiation","authors":"V. Gruzdev","doi":"10.1117/12.754056","DOIUrl":"https://doi.org/10.1117/12.754056","url":null,"abstract":"In this paper we analyze the photo-excitation of electron sub-system of a periodic nano-structure by IR laser radiation. The nano-structure is a 1D super-lattice on surface of dielectric or semiconductor material transparent for the incident radiation. Theoretical description of the photo-excitation is based on the recent modification of the Keldysh theory adapted to the 1D case. We show that two specific regimes of the photo-excitation are possible in the super-lattices: photo-excitation suppression corresponding to decrease of the photo-excitation rate with increasing of laser intensity, and singularity regime corresponding to abrupt increase of the photo-ionization rate. Threshold of the singularity regime is calculated as function of laser wavelength and super-lattice period. The obtained results allow to propose a promising application of the super-lattices as intensity limiters for IR optical systems. In particular, we can calculate the period of the super-lattice to provide limiting of input laser intensity at required level due to multi-photon absorption by electrons of the lattice. Temperature of laser-induced heating resulted from total absorption of an incident laser pulse and diffraction distortions induced by the super-lattice are estimated to confirm possibility of utilizing the super-lattices as the intensity limiters.","PeriodicalId":204978,"journal":{"name":"SPIE Laser Damage","volume":"5 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":"116101573","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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