F. Roubani-Kalantzopoulou, M. Kompitsas, A. Mavropoulos, I. Bassiotis
The increasing need for the recording and monitoring of the marine pollution, as well as the disadvantages usually presented by the conventional methods to qualitatively and quantitatively determine the pollutants in the marine environment, have led to the development of a new method, which is based on the technique of laser induced fluorescence combined with the use of optical fibers. In this work, we present the basic principle of the method and its improvement referred to the appropriate selection of the wavelength excitation: this permits the qualitative determination of gasoline and jet-oil in water. Furthermore, based on the different life-times, we applied the method of time-resolved spectroscopy and succeeded in identifying anthracene and pyrene, in a mixture of both aromatic compounds, despite their spectral overlap and the weak fluorescence of pyrene.
{"title":"Qualitative determination of organic pollutants in an aquatic environment by laser-induced fluorescence combined with optical fibers","authors":"F. Roubani-Kalantzopoulou, M. Kompitsas, A. Mavropoulos, I. Bassiotis","doi":"10.1117/12.316596","DOIUrl":"https://doi.org/10.1117/12.316596","url":null,"abstract":"The increasing need for the recording and monitoring of the marine pollution, as well as the disadvantages usually presented by the conventional methods to qualitatively and quantitatively determine the pollutants in the marine environment, have led to the development of a new method, which is based on the technique of laser induced fluorescence combined with the use of optical fibers. In this work, we present the basic principle of the method and its improvement referred to the appropriate selection of the wavelength excitation: this permits the qualitative determination of gasoline and jet-oil in water. Furthermore, based on the different life-times, we applied the method of time-resolved spectroscopy and succeeded in identifying anthracene and pyrene, in a mixture of both aromatic compounds, despite their spectral overlap and the weak fluorescence of pyrene.","PeriodicalId":373160,"journal":{"name":"GR-I International Conference on New Laser Technologies and Applications","volume":"5 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-07-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114429526","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, a detailed analysis of the transient heat flow in a VCSEL is carried out. The transient thermal response of VCSEL axisymmetric structures is calculated based on a Green's functions method to solve the time- dependent thermal conduction equation. Based on this approach, the heat flow inside the device due to the dominant heat sources in the active and passive layers has been assessed. The influence of the current spreading and the material parameters on the transient thermal response is investigated, and the temporal evolution of the temperature distribution and the lasing wavelength shift are calculated and found to be in good agreement with results obtained by a finite element method. Finally, the time constant of the active layer temperature rise due to a stepwise increase in current for a double-fused long wavelength VCSEL is calculated.
{"title":"Numerical modeling of long-wavelength vertical-cavity surface-emitting semiconductor lasers. II. Transient thermal modeling","authors":"A. Tsigopoulos, V. Paschos","doi":"10.1117/12.316559","DOIUrl":"https://doi.org/10.1117/12.316559","url":null,"abstract":"In this paper, a detailed analysis of the transient heat flow in a VCSEL is carried out. The transient thermal response of VCSEL axisymmetric structures is calculated based on a Green's functions method to solve the time- dependent thermal conduction equation. Based on this approach, the heat flow inside the device due to the dominant heat sources in the active and passive layers has been assessed. The influence of the current spreading and the material parameters on the transient thermal response is investigated, and the temporal evolution of the temperature distribution and the lasing wavelength shift are calculated and found to be in good agreement with results obtained by a finite element method. Finally, the time constant of the active layer temperature rise due to a stepwise increase in current for a double-fused long wavelength VCSEL is calculated.","PeriodicalId":373160,"journal":{"name":"GR-I International Conference on New Laser Technologies and Applications","volume":"24 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-07-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125610561","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 useful tool in working with non-visible optical radiation is a monitor/indicator with an alarm, activated when the irradiance exceeds a preset value. In extending this tool to more applications, this paper describes the design and development of a small active lightweight indicator in two versions, for detecting, observing and responding to almost every preset level of the optical radiation, extended from low up to high optical power densities. The monitor/indicator, in the form of a small cylinder or a pencil or a thick card, with low power consumption and linear response, may be used as active warning element on the side of goggles, spectacles, helmets etc., or as an active element for replacing the laser indication passive cards. The indicator's audible and visible output alarms are like the indication output of the ionizing radiation monitors. The alarm is activated if the irradiance exceeds a preset limit, which may be set equal to maximum permissible exposure. The main parts in both versions are a photodetector and a FET-input operational amplifier, in an optoelectronic integrator and an intensity/frequency converter. This circuit reacts with sufficient accuracy in CW or pulsed radiation down to the optical irradiance.
{"title":"Optoelectronic indicator/warning circuit for detecting and observing the high values of incident optical radiation","authors":"S. Tsitomeneas","doi":"10.1117/12.316562","DOIUrl":"https://doi.org/10.1117/12.316562","url":null,"abstract":"A useful tool in working with non-visible optical radiation is a monitor/indicator with an alarm, activated when the irradiance exceeds a preset value. In extending this tool to more applications, this paper describes the design and development of a small active lightweight indicator in two versions, for detecting, observing and responding to almost every preset level of the optical radiation, extended from low up to high optical power densities. The monitor/indicator, in the form of a small cylinder or a pencil or a thick card, with low power consumption and linear response, may be used as active warning element on the side of goggles, spectacles, helmets etc., or as an active element for replacing the laser indication passive cards. The indicator's audible and visible output alarms are like the indication output of the ionizing radiation monitors. The alarm is activated if the irradiance exceeds a preset limit, which may be set equal to maximum permissible exposure. The main parts in both versions are a photodetector and a FET-input operational amplifier, in an optoelectronic integrator and an intensity/frequency converter. This circuit reacts with sufficient accuracy in CW or pulsed radiation down to the optical irradiance.","PeriodicalId":373160,"journal":{"name":"GR-I International Conference on New Laser Technologies and Applications","volume":"93 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-07-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121939796","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}
Some ultrafast phenomena occurring in an active microcavity have been investigated. This device can behave as an efficient source of non-classical light, when a small number of molecules inside are excited by a femtosecond laser.In this way single photon n > states are generated with anon-classical sub-Poissonian distribution. Multiple excitations of a larger number of molecules can give rise to collective phenomena because of the strong super-radiant ultrafast coupling within the transverse region of the microcavity electromagnetic field. This process has been experimentally studied by means of a high efficiency, single photon, femtosecond non-linear optical gate.
{"title":"Ultrafast phenomena in an active microcavity","authors":"P. Mataloni, O. Jedrkiewicz, F. De Martini","doi":"10.1117/12.316576","DOIUrl":"https://doi.org/10.1117/12.316576","url":null,"abstract":"Some ultrafast phenomena occurring in an active microcavity have been investigated. This device can behave as an efficient source of non-classical light, when a small number of molecules inside are excited by a femtosecond laser.In this way single photon n > states are generated with anon-classical sub-Poissonian distribution. Multiple excitations of a larger number of molecules can give rise to collective phenomena because of the strong super-radiant ultrafast coupling within the transverse region of the microcavity electromagnetic field. This process has been experimentally studied by means of a high efficiency, single photon, femtosecond non-linear optical gate.","PeriodicalId":373160,"journal":{"name":"GR-I International Conference on New Laser Technologies and Applications","volume":"18 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-07-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128283110","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}
Micron-sized deposition and etching of W in WF6 + H2 atmosphere is investigated by local laser-induced heating of thin tungsten layers on quartz substrates. The process is strongly dependent on the partial pressures of the two gases. A process with high amount of hydrogen permits deposition of W, whereas etching of W occurs if the working gas does not contain hydrogen.
{"title":"Laser-induced deposition and etching of tungsten microstructures","authors":"K. Piglmayer, H. Schieche, R. Chabicovsky","doi":"10.1117/12.316606","DOIUrl":"https://doi.org/10.1117/12.316606","url":null,"abstract":"Micron-sized deposition and etching of W in WF6 + H2 atmosphere is investigated by local laser-induced heating of thin tungsten layers on quartz substrates. The process is strongly dependent on the partial pressures of the two gases. A process with high amount of hydrogen permits deposition of W, whereas etching of W occurs if the working gas does not contain hydrogen.","PeriodicalId":373160,"journal":{"name":"GR-I International Conference on New Laser Technologies and Applications","volume":"5 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-07-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130489367","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}
Because of the present success of the Erbium doped fibre amplifiers in telecommunication systems, there is now a trend to look for more compact amplifiers, also based on rare earth doped hosts in wave guide structures, but in the much more compact geometry of short planar wave guides. The shortening of the active length shall be obtain only if one of the following conditions are fuffihled: the active ion concentration-cross-sections product can be increased by three order of magrntude. From basic principle, it is shown that because of the rather weak interaction with the surrounthng, the ion crosssections does not vary a lot when changing the glass host arid that the ion-ion interactions shall fundamentally limit the active ion concentration. Tentative solutions to this problem are presented.
{"title":"Rare-earth-doped active films: basic problems to solve and hints for solutions","authors":"F. Auzel","doi":"10.1117/12.316619","DOIUrl":"https://doi.org/10.1117/12.316619","url":null,"abstract":"Because of the present success of the Erbium doped fibre amplifiers in telecommunication systems, there is now a trend to look for more compact amplifiers, also based on rare earth doped hosts in wave guide structures, but in the much more compact geometry of short planar wave guides. The shortening of the active length shall be obtain only if one of the following conditions are fuffihled: the active ion concentration-cross-sections product can be increased by three order of magrntude. From basic principle, it is shown that because of the rather weak interaction with the surrounthng, the ion crosssections does not vary a lot when changing the glass host arid that the ion-ion interactions shall fundamentally limit the active ion concentration. Tentative solutions to this problem are presented.","PeriodicalId":373160,"journal":{"name":"GR-I International Conference on New Laser Technologies and Applications","volume":"140 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-07-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123305232","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We use optical methods for in-situ diagnostics in pulsed laser deposition of high temperature superconductive thin films. Our interest is focused on the composition modifications experienced by the plume of ablated material during its expansion from the target to the substrate in a molecular oxygen environment, which constitute a key point for the attainment of the correct film stoichiometry. Our diagnostics, based on absorption spectroscopy of atomic oxygen, provide a reliable tool for accurate analysis of the molecular oxygen dissociation involved in the reactive- collisional processes.
{"title":"Diagnostics of the laser deposition process by optical methods","authors":"F. Fuso","doi":"10.1117/12.316603","DOIUrl":"https://doi.org/10.1117/12.316603","url":null,"abstract":"We use optical methods for in-situ diagnostics in pulsed laser deposition of high temperature superconductive thin films. Our interest is focused on the composition modifications experienced by the plume of ablated material during its expansion from the target to the substrate in a molecular oxygen environment, which constitute a key point for the attainment of the correct film stoichiometry. Our diagnostics, based on absorption spectroscopy of atomic oxygen, provide a reliable tool for accurate analysis of the molecular oxygen dissociation involved in the reactive- collisional processes.","PeriodicalId":373160,"journal":{"name":"GR-I International Conference on New Laser Technologies and Applications","volume":"3423 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-07-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129501375","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 convenient cw laser source is demonstrated covering the spectral range 1.6 -1.9 run. The light source is based on the cascaded Raman generation in a standard optical fiber with moderate germarnuin concentration. The new Raman laser can be used as a light source ofpuniping for this particular spectral region.
{"title":"CW laser at 1.6 to 1.9 μm through cascaded fiber Raman","authors":"P. Persephonis","doi":"10.1117/12.316638","DOIUrl":"https://doi.org/10.1117/12.316638","url":null,"abstract":"A convenient cw laser source is demonstrated covering the spectral range 1.6 -1.9 run. The light source is based on the cascaded Raman generation in a standard optical fiber with moderate germarnuin concentration. The new Raman laser can be used as a light source ofpuniping for this particular spectral region.","PeriodicalId":373160,"journal":{"name":"GR-I International Conference on New Laser Technologies and Applications","volume":"21 43","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-07-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114043814","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 goal of this study is to further clarify the influence of the laser parameters on the safety of excimer laser angioplasty and to demonstrate the potential of XeCl laser to be a probe and a fire source simultaneously. On the base of a simple model it is demonstrated that the heat accumulation effects in the XeCl laser irradiated tissues is dependent on the ratio of the laser pulse repetition rate and the tissue thermal diffusion time and that there would not be a thermal injury of the tissues for pulse repetition rates under 15Hz. It was demonstrated that with a specially designed for use with optical fibers and a XeCl excimer laser angioplasty system fluorometer the real time diagnosis of vascular diseases and the feedback control for efficient and safe excimer laser angioplasty are possible.
{"title":"Potential of safe XeCl laser angioplasty","authors":"V. Lyutskanov, N. Minkovski","doi":"10.1117/12.316634","DOIUrl":"https://doi.org/10.1117/12.316634","url":null,"abstract":"The goal of this study is to further clarify the influence of the laser parameters on the safety of excimer laser angioplasty and to demonstrate the potential of XeCl laser to be a probe and a fire source simultaneously. On the base of a simple model it is demonstrated that the heat accumulation effects in the XeCl laser irradiated tissues is dependent on the ratio of the laser pulse repetition rate and the tissue thermal diffusion time and that there would not be a thermal injury of the tissues for pulse repetition rates under 15Hz. It was demonstrated that with a specially designed for use with optical fibers and a XeCl excimer laser angioplasty system fluorometer the real time diagnosis of vascular diseases and the feedback control for efficient and safe excimer laser angioplasty are possible.","PeriodicalId":373160,"journal":{"name":"GR-I International Conference on New Laser Technologies and Applications","volume":"61 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-07-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116704751","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We have studied analytically the theoretical behavior of a Fabry-Perot cavity using a birefringent non-linear material in a polarizer-sample-analyzer system. The working parameter of our device is the direction of polarization of the incident light. Principal results are presented.
{"title":"New laser-based bistability system for optical computing applications","authors":"P. Matzakos, N. Théofanous","doi":"10.1117/12.316583","DOIUrl":"https://doi.org/10.1117/12.316583","url":null,"abstract":"We have studied analytically the theoretical behavior of a Fabry-Perot cavity using a birefringent non-linear material in a polarizer-sample-analyzer system. The working parameter of our device is the direction of polarization of the incident light. Principal results are presented.","PeriodicalId":373160,"journal":{"name":"GR-I International Conference on New Laser Technologies and Applications","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-07-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125819002","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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