Ruben Stahlbaum, L. Röhe, Martin Kleimeyer, B. Günther
Abstract Within the last 10 years the illuminants for automotive exterior lighting shifted nearly completely to LEDs. Due to being semiconductor devices, LEDs behave differently compared to incandescent lamps and xenon bulbs. The paper derives a generalized thermal and geometric LED model. This gains advantage because the data provided in data sheets is different from manufacturer to manufacturer and even from one manufacturer the data is not standardized. So the data is not prepared to be included easily in any development process. In this context “model” mainly refers to a calculation procedure. The data provided in data sheets often has to be digitized. Outgoing from this digitized data a model, based on a smart data combination and polynomial regression, is built up. This model is described in detail and an application to simulations by means of computational fluid dynamics (CFD) is discussed. In doing so a geometric simplification is suggested. This simplification is done in a manner to keep the thermal characteristic of the original LED. The model may be used in different applications such as simulations and design. It allows predicting the thermal status and light output during a virtual development phase, because it inherently calculates the thermal power and light output. This may lead to a more precise estimation of temperatures in lighting systems as well as a prediction of hot lumens.
{"title":"A generalised thermal LED-model and its applications","authors":"Ruben Stahlbaum, L. Röhe, Martin Kleimeyer, B. Günther","doi":"10.1515/aot-2022-0017","DOIUrl":"https://doi.org/10.1515/aot-2022-0017","url":null,"abstract":"Abstract Within the last 10 years the illuminants for automotive exterior lighting shifted nearly completely to LEDs. Due to being semiconductor devices, LEDs behave differently compared to incandescent lamps and xenon bulbs. The paper derives a generalized thermal and geometric LED model. This gains advantage because the data provided in data sheets is different from manufacturer to manufacturer and even from one manufacturer the data is not standardized. So the data is not prepared to be included easily in any development process. In this context “model” mainly refers to a calculation procedure. The data provided in data sheets often has to be digitized. Outgoing from this digitized data a model, based on a smart data combination and polynomial regression, is built up. This model is described in detail and an application to simulations by means of computational fluid dynamics (CFD) is discussed. In doing so a geometric simplification is suggested. This simplification is done in a manner to keep the thermal characteristic of the original LED. The model may be used in different applications such as simulations and design. It allows predicting the thermal status and light output during a virtual development phase, because it inherently calculates the thermal power and light output. This may lead to a more precise estimation of temperatures in lighting systems as well as a prediction of hot lumens.","PeriodicalId":46010,"journal":{"name":"Advanced Optical Technologies","volume":null,"pages":null},"PeriodicalIF":1.8,"publicationDate":"2022-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46651817","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}
Abstract Catalysts are important components in chemical processes because they lower the activation energy and thus determine the rate, efficiency and selectivity of a chemical reaction. This property plays an important role in many of today’s processes, including the electrochemical splitting of water. Due to the continuous development of catalyst materials, they are becoming more complex, which makes a reliable evaluation of physicochemical properties challenging even for modern analytical measurement techniques and industrial manufacturing. We present a fast, vacuum-free and non-destructive analytical approach using multi-sample spectroscopic ellipsometry to determine relevant material parameters such as film thickness, porosity and composition of mesoporous IrOx–TiOy films. Mesoporous IrOx–TiOy films were deposited on Si wafers by sol–gel synthesis, varying the composition of the mixed oxide films between 0 and 100 wt%Ir. The ellipsometric modeling is based on an anisotropic Bruggeman effective medium approximation (a-BEMA) to determine the film thickness and volume fraction of the material and pores. The volume fraction of the material was again modeled using a Bruggeman EMA to determine the chemical composition of the materials. The ellipsometric fitting results were compared with complementary methods, such as scanning electron microscopy (SEM), electron probe microanalysis (EPMA) as well as environmental ellipsometric porosimetry (EEP).
{"title":"Multilevel effective material approximation for modeling ellipsometric measurements on complex porous thin films","authors":"R. Sachse, V. Hodoroaba, R. Kraehnert, A. Hertwig","doi":"10.1515/aot-2022-0007","DOIUrl":"https://doi.org/10.1515/aot-2022-0007","url":null,"abstract":"Abstract Catalysts are important components in chemical processes because they lower the activation energy and thus determine the rate, efficiency and selectivity of a chemical reaction. This property plays an important role in many of today’s processes, including the electrochemical splitting of water. Due to the continuous development of catalyst materials, they are becoming more complex, which makes a reliable evaluation of physicochemical properties challenging even for modern analytical measurement techniques and industrial manufacturing. We present a fast, vacuum-free and non-destructive analytical approach using multi-sample spectroscopic ellipsometry to determine relevant material parameters such as film thickness, porosity and composition of mesoporous IrOx–TiOy films. Mesoporous IrOx–TiOy films were deposited on Si wafers by sol–gel synthesis, varying the composition of the mixed oxide films between 0 and 100 wt%Ir. The ellipsometric modeling is based on an anisotropic Bruggeman effective medium approximation (a-BEMA) to determine the film thickness and volume fraction of the material and pores. The volume fraction of the material was again modeled using a Bruggeman EMA to determine the chemical composition of the materials. The ellipsometric fitting results were compared with complementary methods, such as scanning electron microscopy (SEM), electron probe microanalysis (EPMA) as well as environmental ellipsometric porosimetry (EEP).","PeriodicalId":46010,"journal":{"name":"Advanced Optical Technologies","volume":null,"pages":null},"PeriodicalIF":1.8,"publicationDate":"2022-06-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48278283","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}
Abstract The polarimetric techniques are used in various biomedical applications for a non-contact and fast diagnosis of tissue that is known as optical biopsy approach. These optical modalities provide relevant information on micro-architecture of biological tissue and its alterations induced by different diseases, thus, helping in staging and precise delineation of the pathology zones. In this review, we summarize the work of different research groups on using polarized light for brain tissue studies. This includes the investigations of polarimetric properties of brain tissue (both scattering and optical anisotropy) for brain connectome reconstruction, the visualization of in-plane brain fiber tracts for brain tumor contrast enhancement during neurosurgery, and the histopathology analysis for disease staging in Alzheimer’s subjects. We discuss also further perspectives for the pre-clinical studies of brain with polarized light.
{"title":"Polarimetric techniques for the structural studies and diagnosis of brain","authors":"Omar Rodríguez-Núñez, T. Novikova","doi":"10.1515/aot-2022-0015","DOIUrl":"https://doi.org/10.1515/aot-2022-0015","url":null,"abstract":"Abstract The polarimetric techniques are used in various biomedical applications for a non-contact and fast diagnosis of tissue that is known as optical biopsy approach. These optical modalities provide relevant information on micro-architecture of biological tissue and its alterations induced by different diseases, thus, helping in staging and precise delineation of the pathology zones. In this review, we summarize the work of different research groups on using polarized light for brain tissue studies. This includes the investigations of polarimetric properties of brain tissue (both scattering and optical anisotropy) for brain connectome reconstruction, the visualization of in-plane brain fiber tracts for brain tumor contrast enhancement during neurosurgery, and the histopathology analysis for disease staging in Alzheimer’s subjects. We discuss also further perspectives for the pre-clinical studies of brain with polarized light.","PeriodicalId":46010,"journal":{"name":"Advanced Optical Technologies","volume":null,"pages":null},"PeriodicalIF":1.8,"publicationDate":"2022-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48663365","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}
S. Zollner, F. Abadizaman, C. Emminger, N. Samarasingha
Abstract The temperature dependence of the optical constants of materials (refractive index, absorption and extinction coefficients, and dielectric function) can be determined with spectroscopic ellipsometry over a broad range of temperatures and photon energies or wavelengths. Such results have practical value, for example for applications of optical materials at cryogenic or elevated temperatures. The temperature dependence of optical gaps and their broadenings also provides insight into the scattering of electrons and holes with other quasiparticles, such as phonons or magnons. This review presents a detailed discussion of the experimental considerations for temperature-dependent ellipsometry and selected results for insulators, semiconductors, and metals in the infrared to ultraviolet spectral regions.
{"title":"Spectroscopic ellipsometry from 10 to 700 K","authors":"S. Zollner, F. Abadizaman, C. Emminger, N. Samarasingha","doi":"10.1515/aot-2022-0016","DOIUrl":"https://doi.org/10.1515/aot-2022-0016","url":null,"abstract":"Abstract The temperature dependence of the optical constants of materials (refractive index, absorption and extinction coefficients, and dielectric function) can be determined with spectroscopic ellipsometry over a broad range of temperatures and photon energies or wavelengths. Such results have practical value, for example for applications of optical materials at cryogenic or elevated temperatures. The temperature dependence of optical gaps and their broadenings also provides insight into the scattering of electrons and holes with other quasiparticles, such as phonons or magnons. This review presents a detailed discussion of the experimental considerations for temperature-dependent ellipsometry and selected results for insulators, semiconductors, and metals in the infrared to ultraviolet spectral regions.","PeriodicalId":46010,"journal":{"name":"Advanced Optical Technologies","volume":null,"pages":null},"PeriodicalIF":1.8,"publicationDate":"2022-06-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41254429","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}
Abstract The Mueller matrix is a mathematical description of how light is altered by an optical element or a sample under study. It describes both intensity (irradiance) and polarization changes, including a reduction of the total polarization. Mueller matrix spectroscopic ellipsometry has gained recent popularity in the optics and semiconductor communities as an effective means to characterize complex sample structures and anisotropic materials. While this method is not new, its recent expansion to new fields has left many users with only a pedestrian understanding of the data they collect. This tutorial provides an overview of Mueller matrix spectroscopic ellipsometry with focus on practical aspects for those new to the technique.
{"title":"Mueller matrix spectroscopic ellipsometry","authors":"J. Hilfiker, N. Hong, Stefan Schoeche","doi":"10.1515/aot-2022-0008","DOIUrl":"https://doi.org/10.1515/aot-2022-0008","url":null,"abstract":"Abstract The Mueller matrix is a mathematical description of how light is altered by an optical element or a sample under study. It describes both intensity (irradiance) and polarization changes, including a reduction of the total polarization. Mueller matrix spectroscopic ellipsometry has gained recent popularity in the optics and semiconductor communities as an effective means to characterize complex sample structures and anisotropic materials. While this method is not new, its recent expansion to new fields has left many users with only a pedestrian understanding of the data they collect. This tutorial provides an overview of Mueller matrix spectroscopic ellipsometry with focus on practical aspects for those new to the technique.","PeriodicalId":46010,"journal":{"name":"Advanced Optical Technologies","volume":null,"pages":null},"PeriodicalIF":1.8,"publicationDate":"2022-06-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42140483","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}
Abstract This view highlights a revolutionary change in IR ellipsometry, namely, the incorporation and application of tunable lasers. The presented instrumental developments beyond classical FTIR-based approaches are coming precisely at the right time for today’s demands for in situ, operando and hyperspectral characterization methods required in bioanalytics, catalysis and surface science.
{"title":"Mid-infrared laser ellipsometry: a new era beyond FTIR","authors":"A. Furchner, K. Hinrichs","doi":"10.1515/aot-2022-0013","DOIUrl":"https://doi.org/10.1515/aot-2022-0013","url":null,"abstract":"Abstract This view highlights a revolutionary change in IR ellipsometry, namely, the incorporation and application of tunable lasers. The presented instrumental developments beyond classical FTIR-based approaches are coming precisely at the right time for today’s demands for in situ, operando and hyperspectral characterization methods required in bioanalytics, catalysis and surface science.","PeriodicalId":46010,"journal":{"name":"Advanced Optical Technologies","volume":null,"pages":null},"PeriodicalIF":1.8,"publicationDate":"2022-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41275127","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}
{"title":"Report: Laser World of Photonics 2022","authors":"A. Thoss","doi":"10.1515/aot-2022-0020","DOIUrl":"https://doi.org/10.1515/aot-2022-0020","url":null,"abstract":"","PeriodicalId":46010,"journal":{"name":"Advanced Optical Technologies","volume":null,"pages":null},"PeriodicalIF":1.8,"publicationDate":"2022-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42305667","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}
Abstract The crystalline lens makes an important contribution to the peripheral refraction of the human eye, which may affect the development and progression of myopia. However, little has been known about the peripheral optical features of the crystalline lens and its impacts on the peripheral ocular refraction. This study aims to investigate the relationship between the structural parameters of the crystalline lens and its peripheral power profile over a wide visual field. The peripheral power profile is defined with respect to the entrance and exit pupil centers along the chief rays. Analysis is performed by three-dimensional ray tracing through the gradient refractive index (GRIN) lens models built from measurement data. It has been found that the vergence of the wavefronts at the entrance and the exit pupil centers of the lens show an approximate linear correlation to each other for each field angle. The exponent parameters of the axial refractive index profile and the axial curvature profile, and the asphericity of the posterior lens surface are found to be the most influential parameters in the peripheral power profiles. The study also shows that there can be significantly different, sometimes unrealistic, power profiles in the homogeneous lens model compared with its corresponding GRIN model with the same external geometry. The theoretical findings on the peripheral lens properties provide a new perspective for both wide-field eye modelling and the design of intraocular lenses to achieve normal peripheral vision.
{"title":"Impacts of the gradient-index crystalline lens structure on its peripheral optical power profile","authors":"Qing Li, F. Fang","doi":"10.1515/aot-2022-0003","DOIUrl":"https://doi.org/10.1515/aot-2022-0003","url":null,"abstract":"Abstract The crystalline lens makes an important contribution to the peripheral refraction of the human eye, which may affect the development and progression of myopia. However, little has been known about the peripheral optical features of the crystalline lens and its impacts on the peripheral ocular refraction. This study aims to investigate the relationship between the structural parameters of the crystalline lens and its peripheral power profile over a wide visual field. The peripheral power profile is defined with respect to the entrance and exit pupil centers along the chief rays. Analysis is performed by three-dimensional ray tracing through the gradient refractive index (GRIN) lens models built from measurement data. It has been found that the vergence of the wavefronts at the entrance and the exit pupil centers of the lens show an approximate linear correlation to each other for each field angle. The exponent parameters of the axial refractive index profile and the axial curvature profile, and the asphericity of the posterior lens surface are found to be the most influential parameters in the peripheral power profiles. The study also shows that there can be significantly different, sometimes unrealistic, power profiles in the homogeneous lens model compared with its corresponding GRIN model with the same external geometry. The theoretical findings on the peripheral lens properties provide a new perspective for both wide-field eye modelling and the design of intraocular lenses to achieve normal peripheral vision.","PeriodicalId":46010,"journal":{"name":"Advanced Optical Technologies","volume":null,"pages":null},"PeriodicalIF":1.8,"publicationDate":"2022-05-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42496919","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}
Abstract The article describes the way to calculate the distances, defined by the U.S. Federal Aviation Administration in the AC 70-1B document, essential for the flight safety in the case of illumination of aircraft pilots by laser radiation. FAA’s calculations and presented examples are simplified for the most common cases of a single circular beam, or circular beams sharing the same power, divergence and aperture. Proposed in this article calculation method was extended to multi-beam radiation sources characterized by different wavelengths, different divergences in two perpendicular planes and different powers. The impact of ellipticity of the beams on the calculated distances was shown. The presented analysis may be a supplement to the AC 70-1B document and may serve as a sample approach for those who need to deal with such laser sources. Laser pointers characterized by powers of up to 50 W as well as these with typical powers of several mW were considered. It was shown that even typical 1 mW laser pointers may still distract the aircraft pilots during landing or take-off which may have adverse consequences.
{"title":"Calculation and analysis of laser hazard distances in navigable airspace for multi-beam visible CW laser radiation","authors":"J. Młyńczak","doi":"10.1515/aot-2022-0004","DOIUrl":"https://doi.org/10.1515/aot-2022-0004","url":null,"abstract":"Abstract The article describes the way to calculate the distances, defined by the U.S. Federal Aviation Administration in the AC 70-1B document, essential for the flight safety in the case of illumination of aircraft pilots by laser radiation. FAA’s calculations and presented examples are simplified for the most common cases of a single circular beam, or circular beams sharing the same power, divergence and aperture. Proposed in this article calculation method was extended to multi-beam radiation sources characterized by different wavelengths, different divergences in two perpendicular planes and different powers. The impact of ellipticity of the beams on the calculated distances was shown. The presented analysis may be a supplement to the AC 70-1B document and may serve as a sample approach for those who need to deal with such laser sources. Laser pointers characterized by powers of up to 50 W as well as these with typical powers of several mW were considered. It was shown that even typical 1 mW laser pointers may still distract the aircraft pilots during landing or take-off which may have adverse consequences.","PeriodicalId":46010,"journal":{"name":"Advanced Optical Technologies","volume":null,"pages":null},"PeriodicalIF":1.8,"publicationDate":"2022-05-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48948369","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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