Pub Date : 1998-11-01DOI: 10.1088/0963-9659/7/6/006
P. Ayras, S. Honkanen, K. M. Grace, K. C. Shrouf, P. Katila, M. Leppihalme, A. Tervonen, Xiaoguang Yang, B. Swanson, N. Peyghambarian
We describe a highly sensitive chemical sensor scheme using a channel waveguide with a selective surface coating based on polarimetric Zeeman interferometry. The sensing is based on measurement of the phase difference between TE and TM modes propagating in the anisotropic waveguide structure under exposure to toluene vapour. A real-time and reversible response at low ppm level is observed. Modelling results of the sensor structure to further increase its sensitivity are presented.
{"title":"THIN-FILM CHEMICAL SENSORS WITH WAVEGUIDE ZEEMAN INTERFEROMETRY","authors":"P. Ayras, S. Honkanen, K. M. Grace, K. C. Shrouf, P. Katila, M. Leppihalme, A. Tervonen, Xiaoguang Yang, B. Swanson, N. Peyghambarian","doi":"10.1088/0963-9659/7/6/006","DOIUrl":"https://doi.org/10.1088/0963-9659/7/6/006","url":null,"abstract":"We describe a highly sensitive chemical sensor scheme using a channel waveguide with a selective surface coating based on polarimetric Zeeman interferometry. The sensing is based on measurement of the phase difference between TE and TM modes propagating in the anisotropic waveguide structure under exposure to toluene vapour. A real-time and reversible response at low ppm level is observed. Modelling results of the sensor structure to further increase its sensitivity are presented.","PeriodicalId":20787,"journal":{"name":"Pure and Applied Optics: Journal of The European Optical Society Part A","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1998-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79494918","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}
Pub Date : 1998-11-01DOI: 10.1088/0963-9659/7/6/017
S. Prigarin, B. A. Kargin, U. Oppel
To model fields of broken clouds, we consider two methods based on Gaussian random fields and one method based on truncated random paraboloids. These models are determined by a few parameters only: the amount of cloud, the mean cloud base diameter and the mean cloud height. A field of broken clouds is a realization of such a random field, it is obtained by stochastic simulation and special spectral methods for Gaussian fields. The direct solar radiation S, the scattered transmission T and the albedo A of such a field of broken clouds are obtained by solving the stationary radiation transfer equation. Numerically we do this by variance reduction Monte Carlo methods. Varying the cloud parameters, the angle of incidence of the solar radiation we get interesting new functional relations between S, T and A for visible and infrared wavelengths.
{"title":"Random fields of broken clouds and their associated direct solar radiation, scattered transmission and albedo","authors":"S. Prigarin, B. A. Kargin, U. Oppel","doi":"10.1088/0963-9659/7/6/017","DOIUrl":"https://doi.org/10.1088/0963-9659/7/6/017","url":null,"abstract":"To model fields of broken clouds, we consider two methods based on Gaussian random fields and one method based on truncated random paraboloids. These models are determined by a few parameters only: the amount of cloud, the mean cloud base diameter and the mean cloud height. A field of broken clouds is a realization of such a random field, it is obtained by stochastic simulation and special spectral methods for Gaussian fields. The direct solar radiation S, the scattered transmission T and the albedo A of such a field of broken clouds are obtained by solving the stationary radiation transfer equation. Numerically we do this by variance reduction Monte Carlo methods. Varying the cloud parameters, the angle of incidence of the solar radiation we get interesting new functional relations between S, T and A for visible and infrared wavelengths.","PeriodicalId":20787,"journal":{"name":"Pure and Applied Optics: Journal of The European Optical Society Part A","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1998-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73487470","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}
Pub Date : 1998-11-01DOI: 10.1088/0963-9659/7/6/008
S. Ceccherini, M. Colocci, M. Gurioli, F. Bogani
The distinction between the coherent and the incoherent component of the radiation emitted from resonantly excited material systems is difficult experimentally, particularly when ultra-short optical pulses are used for excitation. We propose an experimental procedure allowing an easy measurement of the two components. The method is completely general and applicable to any kind of physical system; its feasibility is demonstrated on the resonant emission from excitons in a semiconductor quantum well.
{"title":"Coherent versus incoherent resonant emission: an experimental method for easy discrimination and measurement","authors":"S. Ceccherini, M. Colocci, M. Gurioli, F. Bogani","doi":"10.1088/0963-9659/7/6/008","DOIUrl":"https://doi.org/10.1088/0963-9659/7/6/008","url":null,"abstract":"The distinction between the coherent and the incoherent component of the radiation emitted from resonantly excited material systems is difficult experimentally, particularly when ultra-short optical pulses are used for excitation. We propose an experimental procedure allowing an easy measurement of the two components. The method is completely general and applicable to any kind of physical system; its feasibility is demonstrated on the resonant emission from excitons in a semiconductor quantum well.","PeriodicalId":20787,"journal":{"name":"Pure and Applied Optics: Journal of The European Optical Society Part A","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1998-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73786633","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}
Pub Date : 1998-11-01DOI: 10.1088/0963-9659/7/6/009
D. D. Feo, S. Nicola, P. Ferraro, P. Maddalena, G. Pierattini
We propose a method based on an interferometric technique to measure the molecular distortion induced by an incident light beam on a nematic liquid crystal film. An analysis of the fringe pattern generated by means of a Fourier transform method allows comparison of the measurements with the theoretical molecular distribution. From this analysis an estimation of the elastic anisotropy of the liquid crystal is derived which is in good agreement with previous results.
{"title":"A Fourier-transform-based interferometric technique for measuring the elastic anisotropy of a nematic liquid crystal","authors":"D. D. Feo, S. Nicola, P. Ferraro, P. Maddalena, G. Pierattini","doi":"10.1088/0963-9659/7/6/009","DOIUrl":"https://doi.org/10.1088/0963-9659/7/6/009","url":null,"abstract":"We propose a method based on an interferometric technique to measure the molecular distortion induced by an incident light beam on a nematic liquid crystal film. An analysis of the fringe pattern generated by means of a Fourier transform method allows comparison of the measurements with the theoretical molecular distribution. From this analysis an estimation of the elastic anisotropy of the liquid crystal is derived which is in good agreement with previous results.","PeriodicalId":20787,"journal":{"name":"Pure and Applied Optics: Journal of The European Optical Society Part A","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1998-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84921774","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}
Pub Date : 1998-11-01DOI: 10.1088/0963-9659/7/6/004
R. Navarro, N. Franceschini
High-resolution compound eyes of the superposition type have been found in some diurnal insects, suggesting high-quality optics. Here we study whether a superposition eye could potentially achieve a higher resolution than that of a single, diffraction-limited facet, like in modern optical instruments made of a number of facets. We have developed a schematic diffractional model of the particularly acute superposition eye of the diurnal lepidopteran agaristid moth Phalaenoides Tristifica, and estimated the amount of aberrations required to fit the experimental data. Our results show that if the ommatidia were perfect (aberration-free) and perfectly aligned towards a common centre O, the resolution of the superposition image would be about 10 times higher than that provided by a single facet, and this in spite of the large phase lags between the pencils of light stemming from neighbouring ommatidia, due to the spherical geometry of the eye. In the insect species taken as a model system here, however, retinal sampling is too coarse to take full advantage of the high spatial frequency content of the superposition image. We show that the experimental data can be fitted if aberrations such as misalignment are introduced. A corollary of these results is that a superposition compound eye which was better constructed and avoided misalignment would provide its host with a better resolution than its `apposition eye counterpart'. This might explain why some diurnal compound eyes such as that of the fast-flying lepidopteran Macroglossum can afford sampling the focal image with a number of rhabdom exceeding the number of ommatidia (Warrant et al 1998 J. Exp. Biol. at press).
在一些昼夜活动的昆虫身上发现了高分辨率的叠加型复眼，这表明它们具有高质量的光学系统。在这里，我们研究了叠加眼是否有可能实现比单个衍射有限的面更高的分辨率，就像在现代光学仪器中由许多面组成一样。我们建立了一种昼行鳞翅目agaristid Phalaenoides Tristifica的特别急性叠加眼的衍射模型，并估计了与实验数据拟合所需的像差量。我们的研究结果表明，如果小眼是完美的(无像差)，并且完美地对准一个共同的中心O，那么叠加图像的分辨率将比单个面提供的分辨率高10倍左右，尽管由于眼睛的球形几何形状，来自相邻小眼的光笔之间存在较大的相位滞后。然而，在这里作为模型系统的昆虫物种中，视网膜采样过于粗糙，无法充分利用叠加图像的高空间频率含量。实验结果表明，在引入像差的情况下，实验数据是可以拟合的。这些结果的一个推论是，一个更好的结构和避免错位的叠加复眼将为其宿主提供比其“对应眼”更好的分辨率。这也许可以解释为什么一些昼行性复眼，如快速飞行的鳞翅目的复眼，能够以超过小眼数量的横纹纹取样焦点图像(Warrant et al . 1998 J. Exp. Biol.)。在出版社)。
{"title":"LETTER TO THE EDITOR: On image quality of microlens arrays in diurnal superposition eyes","authors":"R. Navarro, N. Franceschini","doi":"10.1088/0963-9659/7/6/004","DOIUrl":"https://doi.org/10.1088/0963-9659/7/6/004","url":null,"abstract":"High-resolution compound eyes of the superposition type have been found in some diurnal insects, suggesting high-quality optics. Here we study whether a superposition eye could potentially achieve a higher resolution than that of a single, diffraction-limited facet, like in modern optical instruments made of a number of facets. We have developed a schematic diffractional model of the particularly acute superposition eye of the diurnal lepidopteran agaristid moth Phalaenoides Tristifica, and estimated the amount of aberrations required to fit the experimental data. Our results show that if the ommatidia were perfect (aberration-free) and perfectly aligned towards a common centre O, the resolution of the superposition image would be about 10 times higher than that provided by a single facet, and this in spite of the large phase lags between the pencils of light stemming from neighbouring ommatidia, due to the spherical geometry of the eye. In the insect species taken as a model system here, however, retinal sampling is too coarse to take full advantage of the high spatial frequency content of the superposition image. We show that the experimental data can be fitted if aberrations such as misalignment are introduced. A corollary of these results is that a superposition compound eye which was better constructed and avoided misalignment would provide its host with a better resolution than its `apposition eye counterpart'. This might explain why some diurnal compound eyes such as that of the fast-flying lepidopteran Macroglossum can afford sampling the focal image with a number of rhabdom exceeding the number of ommatidia (Warrant et al 1998 J. Exp. Biol. at press).","PeriodicalId":20787,"journal":{"name":"Pure and Applied Optics: Journal of The European Optical Society Part A","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1998-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87485762","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}
Pub Date : 1998-11-01DOI: 10.1088/0963-9659/7/6/003
A. García-Valenzuela, J. Saniger
We discuss the possibility of approaching a shot-noise-limited measurement of the difference reflectance due to analyte absorption or adsorption on the surface of a thin film, and estimate the resolution for a variety of cases. When using a 1 mW optical beam, the limit of resolution will commonly correspond to a small or very small fraction of a monolayer of the analyte.
{"title":"LETTER TO THE EDITOR: On the limit to the resolution of photoreflectance techniques for sensing analyte concentration at surfaces","authors":"A. García-Valenzuela, J. Saniger","doi":"10.1088/0963-9659/7/6/003","DOIUrl":"https://doi.org/10.1088/0963-9659/7/6/003","url":null,"abstract":"We discuss the possibility of approaching a shot-noise-limited measurement of the difference reflectance due to analyte absorption or adsorption on the surface of a thin film, and estimate the resolution for a variety of cases. When using a 1 mW optical beam, the limit of resolution will commonly correspond to a small or very small fraction of a monolayer of the analyte.","PeriodicalId":20787,"journal":{"name":"Pure and Applied Optics: Journal of The European Optical Society Part A","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1998-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86648738","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}
Pub Date : 1998-11-01DOI: 10.1088/0963-9659/7/6/021
T. Tudor, I. Vinkler
The problem of spectral analyses, in terms of optical observables, of the time-varying spinorial fields encountered in optics is presented. Time-varying coherency matrices and spectral coherency matrices are introduced. The spectral analyses of the output of a KDP electro-optical modulator is presented as an example. The paper is conceived as a contribution to the development of the language of the optics of observables.
{"title":"Time-varying coherency matrices and spectral coherency matrices","authors":"T. Tudor, I. Vinkler","doi":"10.1088/0963-9659/7/6/021","DOIUrl":"https://doi.org/10.1088/0963-9659/7/6/021","url":null,"abstract":"The problem of spectral analyses, in terms of optical observables, of the time-varying spinorial fields encountered in optics is presented. Time-varying coherency matrices and spectral coherency matrices are introduced. The spectral analyses of the output of a KDP electro-optical modulator is presented as an example. The paper is conceived as a contribution to the development of the language of the optics of observables.","PeriodicalId":20787,"journal":{"name":"Pure and Applied Optics: Journal of The European Optical Society Part A","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1998-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85735396","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}
Pub Date : 1998-11-01DOI: 10.1088/0963-9659/7/6/007
P. Bruscaglioni, C. Flesia, A. Ismaelli, P. Sansoni
Experimental evidence of multiple-scattering effects on lidar returns from clouds, as well as the calculated significance of second and higher orders of scattering, as can be found in the literature, are summarized, together with results of intercomparisons of theoretical and experimental results obtained by different researchers. New comparisons between analytic results and Monte Carlo data are reported, indicating the level of accuracy of predictions relevant to multiple scattering and lidar
{"title":"Multiple scattering and lidar returns","authors":"P. Bruscaglioni, C. Flesia, A. Ismaelli, P. Sansoni","doi":"10.1088/0963-9659/7/6/007","DOIUrl":"https://doi.org/10.1088/0963-9659/7/6/007","url":null,"abstract":"Experimental evidence of multiple-scattering effects on lidar returns from clouds, as well as the calculated significance of second and higher orders of scattering, as can be found in the literature, are summarized, together with results of intercomparisons of theoretical and experimental results obtained by different researchers. New comparisons between analytic results and Monte Carlo data are reported, indicating the level of accuracy of predictions relevant to multiple scattering and lidar","PeriodicalId":20787,"journal":{"name":"Pure and Applied Optics: Journal of The European Optical Society Part A","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1998-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81343492","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}
Pub Date : 1998-11-01DOI: 10.1088/0963-9659/7/6/020
A. Tishchenko
A generalized source method is presented for the resolution of the problem of monochromatic wave propagation in non-homogeneous, isotropic structures. When implemented in the form of an iterative technique, it is demonstrated to give the exact analytical solution of the known problem of propagation in a two half-space structure. When implemented in the form of an integral expression, it is shown to give an exact solution under a normalized numerical convergence criterion. It thus represents a new powerful method for electromagnetic wave propagation in arbitrary structures, and also for the assessment of other resolution techniques proposed so far in optical wave propagation, diffraction and scattering.
{"title":"A generalized source method for wave propagation","authors":"A. Tishchenko","doi":"10.1088/0963-9659/7/6/020","DOIUrl":"https://doi.org/10.1088/0963-9659/7/6/020","url":null,"abstract":"A generalized source method is presented for the resolution of the problem of monochromatic wave propagation in non-homogeneous, isotropic structures. When implemented in the form of an iterative technique, it is demonstrated to give the exact analytical solution of the known problem of propagation in a two half-space structure. When implemented in the form of an integral expression, it is shown to give an exact solution under a normalized numerical convergence criterion. It thus represents a new powerful method for electromagnetic wave propagation in arbitrary structures, and also for the assessment of other resolution techniques proposed so far in optical wave propagation, diffraction and scattering.","PeriodicalId":20787,"journal":{"name":"Pure and Applied Optics: Journal of The European Optical Society Part A","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1998-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80582354","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}
Pub Date : 1998-11-01DOI: 10.1088/0963-9659/7/6/005
S. Prigarin, U. Oppel
By Monte Carlo simulation we investigate the two effects as a result of the specific radiation regime of the cloudy atmosphere caused by multiple light reflection between the clouds and the surface: the increase of solar radiation intensity near the Earth's surface and the decrease of the atmosphere - surface system albedo.
{"title":"Increase of mean radiation intensity and decrease of albedo caused by water clouds: simulation results","authors":"S. Prigarin, U. Oppel","doi":"10.1088/0963-9659/7/6/005","DOIUrl":"https://doi.org/10.1088/0963-9659/7/6/005","url":null,"abstract":"By Monte Carlo simulation we investigate the two effects as a result of the specific radiation regime of the cloudy atmosphere caused by multiple light reflection between the clouds and the surface: the increase of solar radiation intensity near the Earth's surface and the decrease of the atmosphere - surface system albedo.","PeriodicalId":20787,"journal":{"name":"Pure and Applied Optics: Journal of The European Optical Society Part A","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1998-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73503213","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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