The selection of the best laser for a given application is a common problem of laser users. However, a direct relationship between laser intrinsic characteristics and a potential application, risks to make the laser source selection process unilateral and partially mistaken. In fact, the best processing technology for a given application must be chosen. Therefore, the present paper proposes an indirect, more realistic selection process. This process starts from a general laser application definition. Then, it passes through the analysis of the needed laser beam--workpiece material interaction and of the necessary laser technological system. Finally, the selection process ends with the laser processing technology definition, where the choice of the most suitable laser source becomes in fact possible.
{"title":"Lasers for material processing","authors":"A. Nichici, I. David, E. Cicala","doi":"10.1117/12.312759","DOIUrl":"https://doi.org/10.1117/12.312759","url":null,"abstract":"The selection of the best laser for a given application is a common problem of laser users. However, a direct relationship between laser intrinsic characteristics and a potential application, risks to make the laser source selection process unilateral and partially mistaken. In fact, the best processing technology for a given application must be chosen. Therefore, the present paper proposes an indirect, more realistic selection process. This process starts from a general laser application definition. Then, it passes through the analysis of the needed laser beam--workpiece material interaction and of the necessary laser technological system. Finally, the selection process ends with the laser processing technology definition, where the choice of the most suitable laser source becomes in fact possible.","PeriodicalId":383583,"journal":{"name":"ROMOPTO International Conference on Micro- to Nano- Photonics III","volume":"17 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125497048","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}
Real-time accurate positioning of laser beams and optical images on 3D targets, as well as focus correction in the flat field laser scanning, are provided by dynamic focus systems. Commonly used zooming devices involve rather complex driving mechanisms to control the relative motion of the lens systems. A possible, cost-effective alternative to this approach is to use a lens with variable focal length. The design of a dynamic focus system based on this principle is presented, and a suitable driving method, using electrostatic interactions, is also proposed. Dimensional design formulae are given, together with performance evaluation calculations.
{"title":"Electrostatically driven dynamic focus system","authors":"H. Totia, Marius A. Micluţa","doi":"10.1117/12.312737","DOIUrl":"https://doi.org/10.1117/12.312737","url":null,"abstract":"Real-time accurate positioning of laser beams and optical images on 3D targets, as well as focus correction in the flat field laser scanning, are provided by dynamic focus systems. Commonly used zooming devices involve rather complex driving mechanisms to control the relative motion of the lens systems. A possible, cost-effective alternative to this approach is to use a lens with variable focal length. The design of a dynamic focus system based on this principle is presented, and a suitable driving method, using electrostatic interactions, is also proposed. Dimensional design formulae are given, together with performance evaluation calculations.","PeriodicalId":383583,"journal":{"name":"ROMOPTO International Conference on Micro- to Nano- Photonics III","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130140192","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}
V. Craciun, D. Craciun, M. Bunescu, E. Vasile, A. Ioncea, R. Dabu, I. Boyd
The role of the sub-surface explosive boiling mechanism for droplet formation during the pulsed laser deposition of thin films has been examined. For photons with an energy lower than the target optical band-gap, hvEg the surface was much less perturbed. Depth-profile estimations of the temperature profiles inside the laser irradiated targets were also quite different for these two cases. For low optical absorption coefficient (OAC) values, (alpha) < 5 X 104 cm-1, a thick layer of liquid formed whose maximum temperature was located at some point below the surface. Simultaneous to the cavity formation, the droplet density on the surface of the grown films was found to increase by orders of magnitude, indicating a clear connection between the target OAC, the temperature profile, the presence of the cavities and a high droplet density. The decrease of the OAC value during prolonged laser ablation could also explain the gradual increase of the droplet density observed when growing La0.5Sr0.5CoO3 films. Based on these results, we suggest that an important fraction of the droplets on the surface of films grown under laser irradiation conditions where the OAC is smaller than 5 X 104 cm-1 is caused by an explosive sub-surface boiling mechanism.
研究了脉冲激光沉积薄膜过程中，亚表面爆炸沸腾机制对液滴形成的作用。对于能量低于目标光学带隙的光子，hvEg表面的扰动要小得多。在这两种情况下，激光照射目标内部温度分布的深度轮廓估计也有很大的不同。当光学吸收系数(OAC)值(alpha) < 5 X 104 cm-1时，形成一层较厚的液体，其最高温度位于表面以下的某一点。在形成空腔的同时，发现生长薄膜表面的液滴密度增加了几个数量级，这表明目标OAC、温度分布、空腔的存在和高液滴密度之间存在明确的联系。长时间激光烧蚀过程中OAC值的降低也可以解释在生长La0.5Sr0.5CoO3薄膜时所观察到的液滴密度逐渐增加的原因。基于这些结果，我们认为在激光照射条件下生长的薄膜表面的液滴中有很大一部分是由爆炸的亚表面沸腾机制引起的，其中OAC小于5 X 104 cm-1。
{"title":"Mechanisms of droplet formation in pulsed laser growth of thin oxide films","authors":"V. Craciun, D. Craciun, M. Bunescu, E. Vasile, A. Ioncea, R. Dabu, I. Boyd","doi":"10.1117/12.312756","DOIUrl":"https://doi.org/10.1117/12.312756","url":null,"abstract":"The role of the sub-surface explosive boiling mechanism for droplet formation during the pulsed laser deposition of thin films has been examined. For photons with an energy lower than the target optical band-gap, hvEg the surface was much less perturbed. Depth-profile estimations of the temperature profiles inside the laser irradiated targets were also quite different for these two cases. For low optical absorption coefficient (OAC) values, (alpha) < 5 X 104 cm-1, a thick layer of liquid formed whose maximum temperature was located at some point below the surface. Simultaneous to the cavity formation, the droplet density on the surface of the grown films was found to increase by orders of magnitude, indicating a clear connection between the target OAC, the temperature profile, the presence of the cavities and a high droplet density. The decrease of the OAC value during prolonged laser ablation could also explain the gradual increase of the droplet density observed when growing La0.5Sr0.5CoO3 films. Based on these results, we suggest that an important fraction of the droplets on the surface of films grown under laser irradiation conditions where the OAC is smaller than 5 X 104 cm-1 is caused by an explosive sub-surface boiling mechanism.","PeriodicalId":383583,"journal":{"name":"ROMOPTO International Conference on Micro- to Nano- Photonics III","volume":"23 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124497568","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}
Excimer lasers are an excellent instrument for performing photorefractive keratotomy, PRK. The UV light from the laser causes an ablation of the cornea in proportion to the intensity of the light. The primary characteristic essential to successful PRK is the uniformity of the Top Hat, or working portion of the laser beam. In order for this intensity profile to be sufficiently uniform for PRK, it is essential to periodically measure the equality of the laser beam profile. This ensures that the laser continues to operate properly and provide the expected performance.
{"title":"Electronic-beam analysis of excimer lasers used for photorefractive keratotomy","authors":"C. Roundy","doi":"10.1117/12.312826","DOIUrl":"https://doi.org/10.1117/12.312826","url":null,"abstract":"Excimer lasers are an excellent instrument for performing photorefractive keratotomy, PRK. The UV light from the laser causes an ablation of the cornea in proportion to the intensity of the light. The primary characteristic essential to successful PRK is the uniformity of the Top Hat, or working portion of the laser beam. In order for this intensity profile to be sufficiently uniform for PRK, it is essential to periodically measure the equality of the laser beam profile. This ensures that the laser continues to operate properly and provide the expected performance.","PeriodicalId":383583,"journal":{"name":"ROMOPTO International Conference on Micro- to Nano- Photonics III","volume":"46 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121197997","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 capabilities of off-nadir satellite observing directional variations in terrestrial surface reflectance, not yet sufficiently present in operational satellite series, are expected to be developed in the near future. The main objective of the paper is to study and modeling the atmospheric effects on the typical angular reflectance characteristics of vegetation surfaces in the visible and near-infrared regions. For the evaluation of the atmospheric contribution to the satellite data, radiative transfer model simulations, with ground radiometric measurements have been performed. The paper discusses the signatures that the atmosphere imposes on the angular distribution of the emerging solar radiation above aerosol-loaded atmosphere. The model calculations have also showed that some atmospheric-invariant features of the angular reflectance distribution, like the aerosol forward scattering peak or the hot spot in the antisolar direction, may be used as discriminant surface reflectance characteristics in the case of low aerosol- loaded atmosphere.
{"title":"Modeling of atmospheric effects on the angular reflectance characteristics of vegetation canopies","authors":"G. Stancalie","doi":"10.1117/12.312741","DOIUrl":"https://doi.org/10.1117/12.312741","url":null,"abstract":"The capabilities of off-nadir satellite observing directional variations in terrestrial surface reflectance, not yet sufficiently present in operational satellite series, are expected to be developed in the near future. The main objective of the paper is to study and modeling the atmospheric effects on the typical angular reflectance characteristics of vegetation surfaces in the visible and near-infrared regions. For the evaluation of the atmospheric contribution to the satellite data, radiative transfer model simulations, with ground radiometric measurements have been performed. The paper discusses the signatures that the atmosphere imposes on the angular distribution of the emerging solar radiation above aerosol-loaded atmosphere. The model calculations have also showed that some atmospheric-invariant features of the angular reflectance distribution, like the aerosol forward scattering peak or the hot spot in the antisolar direction, may be used as discriminant surface reflectance characteristics in the case of low aerosol- loaded atmosphere.","PeriodicalId":383583,"journal":{"name":"ROMOPTO International Conference on Micro- to Nano- Photonics III","volume":"85 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126935718","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. Anghel, I. Iova, Stefan Levai, I. Iorga-Simăn, I. Iosub
Sedimentation of the suspension process is important, especially in pollution, biologic liquids or polymers studies. Unlike the usual methods, as those using pipettes, areometer or balances, the optical ones are nondestructive and more accurate. During sedimentation produced by the braked fall of the solid particles in suspension, fluctuations produced by an opposite vertical diffusion occur; this process is lost using the chemical methods, which weight the mass fallen on a submersed plate. We used a scattering method, based on the attenuation of a laser beam which, in the absence of absorption, describes the variation of solid particles' concentration in the suspension.
{"title":"Optical studies on sedimentation of suspensions","authors":"S. Anghel, I. Iova, Stefan Levai, I. Iorga-Simăn, I. Iosub","doi":"10.1117/12.312708","DOIUrl":"https://doi.org/10.1117/12.312708","url":null,"abstract":"Sedimentation of the suspension process is important, especially in pollution, biologic liquids or polymers studies. Unlike the usual methods, as those using pipettes, areometer or balances, the optical ones are nondestructive and more accurate. During sedimentation produced by the braked fall of the solid particles in suspension, fluctuations produced by an opposite vertical diffusion occur; this process is lost using the chemical methods, which weight the mass fallen on a submersed plate. We used a scattering method, based on the attenuation of a laser beam which, in the absence of absorption, describes the variation of solid particles' concentration in the suspension.","PeriodicalId":383583,"journal":{"name":"ROMOPTO International Conference on Micro- to Nano- Photonics III","volume":"62 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127099679","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 inexpensive optical devices using small silica-gel spheres are presented. The silica-gel spheres of good quality are investigated under the microscope. These sphere presents some particularities which make them very useful in applications like interferometry, hygrometry and optical microscopy. Such small spheres may be doped with microcrystals or dye solution in order to study a large range of nonlinear phenomena. Experimental studies have been performed on the silica spheres as alternative media for laser action using a pulsed CuBr laser as excitation source.
{"title":"Optical devices with silica-gel small spheres","authors":"A. Preda, E. Scarlat, L. Preda, I. Popescu","doi":"10.1117/12.312753","DOIUrl":"https://doi.org/10.1117/12.312753","url":null,"abstract":"Some inexpensive optical devices using small silica-gel spheres are presented. The silica-gel spheres of good quality are investigated under the microscope. These sphere presents some particularities which make them very useful in applications like interferometry, hygrometry and optical microscopy. Such small spheres may be doped with microcrystals or dye solution in order to study a large range of nonlinear phenomena. Experimental studies have been performed on the silica spheres as alternative media for laser action using a pulsed CuBr laser as excitation source.","PeriodicalId":383583,"journal":{"name":"ROMOPTO International Conference on Micro- to Nano- Photonics III","volume":"75 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127351514","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}
Tavi Ciuchita, M. Usurelu, C. Antipa, Mihaela Vlăiculescu, E. Ionescu
The authors tried to verify the efficacy of Low Power Laser (LPL) in scalp alopecia and crural ulcers of different causes. Laser used was (red diode, continuous emission, 8 mW power, wave length 670 nm spot size about 5 mm diameter on some points 1 - 2 minutes per point. We also use as control classical therapy. Before, during and after treatment, histological samples were done for alopecia. For laser groups (alopecia and ulcers) the results were rather superior and in a three or twice time shorter than control group. We conclude that LPL therapy is a very useful complementary method for the treatment of scalp alopecia and crural ulcers.
{"title":"Low-power laser use in the treatment of alopecia and crural ulcers","authors":"Tavi Ciuchita, M. Usurelu, C. Antipa, Mihaela Vlăiculescu, E. Ionescu","doi":"10.1117/12.312657","DOIUrl":"https://doi.org/10.1117/12.312657","url":null,"abstract":"The authors tried to verify the efficacy of Low Power Laser (LPL) in scalp alopecia and crural ulcers of different causes. Laser used was (red diode, continuous emission, 8 mW power, wave length 670 nm spot size about 5 mm diameter on some points 1 - 2 minutes per point. We also use as control classical therapy. Before, during and after treatment, histological samples were done for alopecia. For laser groups (alopecia and ulcers) the results were rather superior and in a three or twice time shorter than control group. We conclude that LPL therapy is a very useful complementary method for the treatment of scalp alopecia and crural ulcers.","PeriodicalId":383583,"journal":{"name":"ROMOPTO International Conference on Micro- to Nano- Photonics III","volume":"46 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127376550","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 a unitary approach generally used in quantum optics, we consider Lindblad's Markovian master equation and the non- Markovian master equation of Ford, Lewis and O'Connell. We show that the second-order master equation in the hierarchy obtained from a Krylov-Bogoliubov expansion corresponds to the Born approximation. By time averaging, and neglecting the rapidly varying terms, Lindblad's master equation is obtained. With these two equations, we calculate the decay spectrum. We find that for rather low dissipated energies, only the non-Markovian master equation provides correct results. Based on the independent oscillator model of the dissipative coupling, explicit expressions of the dissipative coefficients are obtained.
{"title":"Non-Markovian effects in dissipative systems","authors":"E. Stefanescu, P. Sterian","doi":"10.1117/12.312679","DOIUrl":"https://doi.org/10.1117/12.312679","url":null,"abstract":"In a unitary approach generally used in quantum optics, we consider Lindblad's Markovian master equation and the non- Markovian master equation of Ford, Lewis and O'Connell. We show that the second-order master equation in the hierarchy obtained from a Krylov-Bogoliubov expansion corresponds to the Born approximation. By time averaging, and neglecting the rapidly varying terms, Lindblad's master equation is obtained. With these two equations, we calculate the decay spectrum. We find that for rather low dissipated energies, only the non-Markovian master equation provides correct results. Based on the independent oscillator model of the dissipative coupling, explicit expressions of the dissipative coefficients are obtained.","PeriodicalId":383583,"journal":{"name":"ROMOPTO International Conference on Micro- to Nano- Photonics III","volume":"16 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132940713","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}
Arrhenius plots and current-voltage characteristics were studied for natural quartz samples, in different conditions of air- sweeping time, of temperature, of electrodes (with or without any source of positive ions). Some observations about the influence of the ionic space charge limited current are made. Some dependencies of ionic current versus voltage were found.
{"title":"Ionic space-charge-limited currents in natural quartz crystal","authors":"I. Enculescu, B. Iliescu","doi":"10.1117/12.312762","DOIUrl":"https://doi.org/10.1117/12.312762","url":null,"abstract":"Arrhenius plots and current-voltage characteristics were studied for natural quartz samples, in different conditions of air- sweeping time, of temperature, of electrodes (with or without any source of positive ions). Some observations about the influence of the ionic space charge limited current are made. Some dependencies of ionic current versus voltage were found.","PeriodicalId":383583,"journal":{"name":"ROMOPTO International Conference on Micro- to Nano- Photonics III","volume":"44 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121200350","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}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：