The use of capacitive Radio-Frequency discharges for the excitation of thin diffusion cooled regions of gas has caused a remarkable breakthrough in the establishment of new CO2 laser sources. Indeed this technique allows specific power loadings more than one order of magnitude higher than those of conventional slow-flow lasers. At the same time it enables efficient laser operation in sealed or quasi-sealed conditions determining an enormous advantage of these sources over fast-flow ones.Advantages are also determined by the potentiality of pulsing this kind of discharge at high repetition rates, in the range 1-10 kHz. Triggered by these considerations a lot of R and D efforts have been made in this field during the laser decade, giving rise to rugged and extremely compact CO2 laser sources in the 100-2000 W power segment, useful in medical as well as in low-power industrial applications. To obtain this result several problems had to be faced such as the attainment of a uniform plasma excitation in large area discharges or the extraction of a good quality beam form non-conventional gain region formats. The solutions adopted so far are reviewed, hints on further developments are given.
{"title":"Diffusion-cooled radio-frequency-excited CO2 lasers","authors":"A. Lapucci","doi":"10.1117/12.316575","DOIUrl":"https://doi.org/10.1117/12.316575","url":null,"abstract":"The use of capacitive Radio-Frequency discharges for the excitation of thin diffusion cooled regions of gas has caused a remarkable breakthrough in the establishment of new CO2 laser sources. Indeed this technique allows specific power loadings more than one order of magnitude higher than those of conventional slow-flow lasers. At the same time it enables efficient laser operation in sealed or quasi-sealed conditions determining an enormous advantage of these sources over fast-flow ones.Advantages are also determined by the potentiality of pulsing this kind of discharge at high repetition rates, in the range 1-10 kHz. Triggered by these considerations a lot of R and D efforts have been made in this field during the laser decade, giving rise to rugged and extremely compact CO2 laser sources in the 100-2000 W power segment, useful in medical as well as in low-power industrial applications. To obtain this result several problems had to be faced such as the attainment of a uniform plasma excitation in large area discharges or the extraction of a good quality beam form non-conventional gain region formats. The solutions adopted so far are reviewed, hints on further developments are given.","PeriodicalId":373160,"journal":{"name":"GR-I International Conference on New Laser Technologies and Applications","volume":"98 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":"130068278","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}
Konstantinos N. Halkiotis, D. Yova, N. Uzunoglou, G. Papastergiou, S. Matakias, I. Koukouvinos
The effectiveness of photodynamic treatment modality has been proven experimentally for a large variety of tumors, during the last years. This therapy utilizes the combined action of light and photosensitizing drug. Until now, a disadvantage of PDT has be the low tissue penetration of light, at the wavelengths of most commonly available lasers, for clinical studies. The red wavelength offers the advantage of increased penetration depth in tissue, in addition several new wavelength offers the advantage of increased penetration depth in tissue, in addition several new photosensitizers present absorption band at the region 630nm to 690nm. The development of high power red diode laser system for photodynamic therapy, has provided a cost effective alternative to existing lasers for use in PDT. This paper will describe the system design, development and performance of a diode laser system, connected with a fiber optic facility, to be used for PDT. The system was based on a high power semiconductor diode laser emitting at 655nm. The laser output power was approximately 60mW at the output of a 62.5/125/900 micron fiber optic probe. FUll technical details and optical performance characteristics of the system will be discussed in this paper.
{"title":"Development of a red diode laser system for photodynamic therapy","authors":"Konstantinos N. Halkiotis, D. Yova, N. Uzunoglou, G. Papastergiou, S. Matakias, I. Koukouvinos","doi":"10.1117/12.316628","DOIUrl":"https://doi.org/10.1117/12.316628","url":null,"abstract":"The effectiveness of photodynamic treatment modality has been proven experimentally for a large variety of tumors, during the last years. This therapy utilizes the combined action of light and photosensitizing drug. Until now, a disadvantage of PDT has be the low tissue penetration of light, at the wavelengths of most commonly available lasers, for clinical studies. The red wavelength offers the advantage of increased penetration depth in tissue, in addition several new wavelength offers the advantage of increased penetration depth in tissue, in addition several new photosensitizers present absorption band at the region 630nm to 690nm. The development of high power red diode laser system for photodynamic therapy, has provided a cost effective alternative to existing lasers for use in PDT. This paper will describe the system design, development and performance of a diode laser system, connected with a fiber optic facility, to be used for PDT. The system was based on a high power semiconductor diode laser emitting at 655nm. The laser output power was approximately 60mW at the output of a 62.5/125/900 micron fiber optic probe. FUll technical details and optical performance characteristics of the system will be discussed in this paper.","PeriodicalId":373160,"journal":{"name":"GR-I International Conference on New Laser Technologies and Applications","volume":"7 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":"127975864","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}
C. Fotakis, V. Zafiropulos, V. Tornari, D. Anglos, C. Balas, S. Georgiou, I. Zergioti
Several aspects of the applications of laser technology in cleaning and diagnostics of painted artworks are reviewed. Laser and material parameter studies leading to the optimization of the cleaning process are presented while the use of spectroscopic techniques for obtaining information on the mechanism of the ablation process and probe possible photochemical effects is discussed. Furthermore, holographic interferometric techniques for detecting possible mechanical stress induced by the laser during the cleaning process are employed and preliminary result are shown. Finally, examples of the applications of imaging techniques in artwork diagnostics are presented.
{"title":"Lasers in the conservation of painted artworks","authors":"C. Fotakis, V. Zafiropulos, V. Tornari, D. Anglos, C. Balas, S. Georgiou, I. Zergioti","doi":"10.1117/12.316602","DOIUrl":"https://doi.org/10.1117/12.316602","url":null,"abstract":"Several aspects of the applications of laser technology in cleaning and diagnostics of painted artworks are reviewed. Laser and material parameter studies leading to the optimization of the cleaning process are presented while the use of spectroscopic techniques for obtaining information on the mechanism of the ablation process and probe possible photochemical effects is discussed. Furthermore, holographic interferometric techniques for detecting possible mechanical stress induced by the laser during the cleaning process are employed and preliminary result are shown. Finally, examples of the applications of imaging techniques in artwork diagnostics are presented.","PeriodicalId":373160,"journal":{"name":"GR-I International Conference on New Laser Technologies and Applications","volume":"52 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":"128967988","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}
Synthetic diamond, deposited by Chemical Vapour Deposition (CVD), is becoming an interesting alternative for ZnSe as a window material for high power CO lasers. Although the infrared absorption of CVD-dianiond is higher than of ZnSe, this drawback is largely overruled by its better thermal conductivity, leading to smaller temperature gradients in the window and hence a less distorted laser beam. Electronic Speckle Pattern Interferometry (ESPI) is applied to study the on-line deformation of ZnSe and CVD-diamond anti-reflective coated output coupler windows exposed to a high power CO laser beam. It is seen that a ZnSe window already starts deforming at moderate beam power (100 W), while a diamond window does not deform considerably up to a beam power of 700 W.
{"title":"ESPI-characterization of online deformations of CVD-diamond output coupler windows in high-power IR lasers","authors":"B. Depuydt, P. Boone, Piet Union, P. Muys","doi":"10.1117/12.316630","DOIUrl":"https://doi.org/10.1117/12.316630","url":null,"abstract":"Synthetic diamond, deposited by Chemical Vapour Deposition (CVD), is becoming an interesting alternative for ZnSe as a window material for high power CO lasers. Although the infrared absorption of CVD-dianiond is higher than of ZnSe, this drawback is largely overruled by its better thermal conductivity, leading to smaller temperature gradients in the window and hence a less distorted laser beam. Electronic Speckle Pattern Interferometry (ESPI) is applied to study the on-line deformation of ZnSe and CVD-diamond anti-reflective coated output coupler windows exposed to a high power CO laser beam. It is seen that a ZnSe window already starts deforming at moderate beam power (100 W), while a diamond window does not deform considerably up to a beam power of 700 W.","PeriodicalId":373160,"journal":{"name":"GR-I International Conference on New Laser Technologies and Applications","volume":"16 12","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-07-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"120972918","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}
M. Koukourakis, A. Giatromanolaki, J. Skarlatos, L. Kosma, N. Apostolikas, K. Beroukas
PDT cytotoxicity is likely to occur through photooxidative reactions. In that way mechanisms that define poor oxygenation should be involved in defining resistance to photo-dynamic treatment (PDT). On the other hand bcl-2 anti- apoptotic protein has been shown to delay cell death and protect cells from toxic oxidative products. We examined 134 specimens from T1,2-NO,1 staged patients treated with surgery alone. Specimens were immunohistochemically examined for vascular grade using the JC70 MoAb, and bcl-2 oncoprotein expression. Bcl-2 expression correlated with low vascular grade. Only 3/27 of bcl2+ case had high angiogenesis vs. 34/107 of cases without bcl-2 expression. In the present study we provide evidence that bcl-2 overexpression directly suppresses angiogenesis in non-small cell lung cancer, which obviously results in decreased blood supply and oxygenation. This finding implies that reduced intratumoral angiogenesis and immortalizing oncoprotein overexpression are linked to each other and may have a role in defining tumors resistant to PDT.
{"title":"Bcl-2 anti-apoptotic oncoprotein suppresses angiogenesis in non-small cell lung cancer: implications in resistance to photodynamic treatment?","authors":"M. Koukourakis, A. Giatromanolaki, J. Skarlatos, L. Kosma, N. Apostolikas, K. Beroukas","doi":"10.1117/12.316631","DOIUrl":"https://doi.org/10.1117/12.316631","url":null,"abstract":"PDT cytotoxicity is likely to occur through photooxidative reactions. In that way mechanisms that define poor oxygenation should be involved in defining resistance to photo-dynamic treatment (PDT). On the other hand bcl-2 anti- apoptotic protein has been shown to delay cell death and protect cells from toxic oxidative products. We examined 134 specimens from T1,2-NO,1 staged patients treated with surgery alone. Specimens were immunohistochemically examined for vascular grade using the JC70 MoAb, and bcl-2 oncoprotein expression. Bcl-2 expression correlated with low vascular grade. Only 3/27 of bcl2+ case had high angiogenesis vs. 34/107 of cases without bcl-2 expression. In the present study we provide evidence that bcl-2 overexpression directly suppresses angiogenesis in non-small cell lung cancer, which obviously results in decreased blood supply and oxygenation. This finding implies that reduced intratumoral angiogenesis and immortalizing oncoprotein overexpression are linked to each other and may have a role in defining tumors resistant to PDT.","PeriodicalId":373160,"journal":{"name":"GR-I International Conference on New Laser Technologies and Applications","volume":"2012 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":"121351111","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 unsteady velocity fields downstream of a cylinder and of a double-circular arc blade under an angle of attack were studied by applying the particle image velocimetry (PIV) technique. The experiments were conducted in a small free- surface water tunnel in the laboratory of hydraulic machines of the National Technical University of Athens. The statistical mean displacements of particles suspended into the fluid, corresponding to two different frames a certain time interval apart, were computed by employing the cross- correlation technique. The result of this analysis was the computation of about 1000 velocity vectors for each pair of frames. Based on this information, it was possible to detect and quantify the interesting flow phenomenon of vortex shedding, like the motion of coherent vortical structures shed into the flow, compute their circulation and vorticity as a function of space and time as well as calculate the forces exerted upon the bodies by the fluid.
{"title":"Study of vortical structures by means of particle image velocimetry","authors":"A. Kostis, D. Mathioulakis","doi":"10.1117/12.316601","DOIUrl":"https://doi.org/10.1117/12.316601","url":null,"abstract":"The unsteady velocity fields downstream of a cylinder and of a double-circular arc blade under an angle of attack were studied by applying the particle image velocimetry (PIV) technique. The experiments were conducted in a small free- surface water tunnel in the laboratory of hydraulic machines of the National Technical University of Athens. The statistical mean displacements of particles suspended into the fluid, corresponding to two different frames a certain time interval apart, were computed by employing the cross- correlation technique. The result of this analysis was the computation of about 1000 velocity vectors for each pair of frames. Based on this information, it was possible to detect and quantify the interesting flow phenomenon of vortex shedding, like the motion of coherent vortical structures shed into the flow, compute their circulation and vorticity as a function of space and time as well as calculate the forces exerted upon the bodies by the fluid.","PeriodicalId":373160,"journal":{"name":"GR-I International Conference on New Laser Technologies and Applications","volume":"3 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":"131206205","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}
This paper presents an experimental technique for measurement of the contrast ratio of ultrashort UV pulses. The multiple shot device based on the scheme of difference frequency generation is, to our knowledge, the only cross correlator in the UV so far, which offers a dynamic range of >= 107 and operates with input pulse energies as low as 5 (mu) J. Changing the cross correlator into single shot mode, the temporal shape of the UV pulse can be measured.
{"title":"High-dynamic-range measurement of the temporal contrast of ultrashort UV pulses","authors":"K. Osvay, I. Ross, J. Lister, C. Hooker","doi":"10.1117/12.316577","DOIUrl":"https://doi.org/10.1117/12.316577","url":null,"abstract":"This paper presents an experimental technique for measurement of the contrast ratio of ultrashort UV pulses. The multiple shot device based on the scheme of difference frequency generation is, to our knowledge, the only cross correlator in the UV so far, which offers a dynamic range of >= 107 and operates with input pulse energies as low as 5 (mu) J. Changing the cross correlator into single shot mode, the temporal shape of the UV pulse can be measured.","PeriodicalId":373160,"journal":{"name":"GR-I International Conference on New Laser Technologies and Applications","volume":"12 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":"123948218","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}
N. Minkovski, V. Lyutskanov, I. Chaltakov, I. Divliansky
For the first time stimulated Raman scattering (SRS) in multimode silica fibers pumped with long XeCl laser pulses has been observed. The spectral and temporal development of SRS both experimentally and theoretically have been studied. Two orders of SRS have been obtained in the 311 divided by 317 nm spectral region. The experimental result are in good agreement with computer simulations of SRS in which effects of self- and cross-phase modulation and group velocity dispersion are negligible. In the numerical model are included experimentally measured spectra of the Raman gain curve and the pump laser spectra.
{"title":"Stimulated Raman scattering of long XeCl laser pulses in multimode silica fibers","authors":"N. Minkovski, V. Lyutskanov, I. Chaltakov, I. Divliansky","doi":"10.1117/12.316580","DOIUrl":"https://doi.org/10.1117/12.316580","url":null,"abstract":"For the first time stimulated Raman scattering (SRS) in multimode silica fibers pumped with long XeCl laser pulses has been observed. The spectral and temporal development of SRS both experimentally and theoretically have been studied. Two orders of SRS have been obtained in the 311 divided by 317 nm spectral region. The experimental result are in good agreement with computer simulations of SRS in which effects of self- and cross-phase modulation and group velocity dispersion are negligible. In the numerical model are included experimentally measured spectra of the Raman gain curve and the pump laser spectra.","PeriodicalId":373160,"journal":{"name":"GR-I International Conference on New Laser Technologies and Applications","volume":"7 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":"124055919","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 rate of spontaneous radiative recombination and gain coefficient for the high-doping superlattices versus the pump current are calculated in the model with no k-selection rule. Results for the inversion current density and differential gain at suitable design of superlattice parameters are presented.
{"title":"Laser parameters of n-i-p-i crystals","authors":"Dmitrii Ushakov, V. Kononenko","doi":"10.1117/12.316565","DOIUrl":"https://doi.org/10.1117/12.316565","url":null,"abstract":"The rate of spontaneous radiative recombination and gain coefficient for the high-doping superlattices versus the pump current are calculated in the model with no k-selection rule. Results for the inversion current density and differential gain at suitable design of superlattice parameters are presented.","PeriodicalId":373160,"journal":{"name":"GR-I International Conference on New Laser Technologies and Applications","volume":"27 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":"121797134","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}
C. Andreouli, S. Christoulakis, T. Efthimiopoulos, A. Tsetsekou, M. Holiastou, C. Panagopoulos
The morphological and compositional changes which take place during the laser irradiation of YBCO targets are discussed. The understanding of the evolution of target composition, will lead to better control of film quality. In the case stated here, a XeCl excimer laser was used to irradiate rotated and also non-rotated YBa2Cu3O7-x targets. The modified surface of these targets was systematically studied by scanning electron microscopy and energy dispersive x-ray microanalysis. It was observed that some crucial deposition parameters, such as the number of pulses and fluence has a strong effect on the roughening of the target. A comparative study was done on the derived High-Tc superconducting thin films. It was shown that the conditions during the preablation procedure which affect the target surface morphology correlate closely with the appearance of laser droplets on the film surface.
{"title":"UV laser beam/YBCO target interaction for optimum preablation for the growth of YBCO thin films","authors":"C. Andreouli, S. Christoulakis, T. Efthimiopoulos, A. Tsetsekou, M. Holiastou, C. Panagopoulos","doi":"10.1117/12.316618","DOIUrl":"https://doi.org/10.1117/12.316618","url":null,"abstract":"The morphological and compositional changes which take place during the laser irradiation of YBCO targets are discussed. The understanding of the evolution of target composition, will lead to better control of film quality. In the case stated here, a XeCl excimer laser was used to irradiate rotated and also non-rotated YBa2Cu3O7-x targets. The modified surface of these targets was systematically studied by scanning electron microscopy and energy dispersive x-ray microanalysis. It was observed that some crucial deposition parameters, such as the number of pulses and fluence has a strong effect on the roughening of the target. A comparative study was done on the derived High-Tc superconducting thin films. It was shown that the conditions during the preablation procedure which affect the target surface morphology correlate closely with the appearance of laser droplets on the film surface.","PeriodicalId":373160,"journal":{"name":"GR-I International Conference on New Laser Technologies and Applications","volume":"32 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":"122156315","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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