One of the three methods specified for the practical realization of the meter uses molecular transitions. He-Ne lasers operating at 633 nm wavelength and frequency stabilized by saturated absorption in 127I2 were built at the National Institute for Lasers, Plasma and Radiation Physics, Laser Department and their performances tested in international comparisons during last four years at the Bureau International des Poids et Mesures (BIPM. 1993, 1995), at the Institute for Metrology `Gustavo Collonetti' (IMGC, 1994) and at the Institute for Scientific Instruments (ISI, 1996). Comparative results regarding frequency difference, repeatability and stability are presented. Results proved a good reproducibility of the performances during the time.
{"title":"Romanian primary length standards involved in international comparisons","authors":"G. Popescu","doi":"10.1117/12.312717","DOIUrl":"https://doi.org/10.1117/12.312717","url":null,"abstract":"One of the three methods specified for the practical realization of the meter uses molecular transitions. He-Ne lasers operating at 633 nm wavelength and frequency stabilized by saturated absorption in 127I2 were built at the National Institute for Lasers, Plasma and Radiation Physics, Laser Department and their performances tested in international comparisons during last four years at the Bureau International des Poids et Mesures (BIPM. 1993, 1995), at the Institute for Metrology `Gustavo Collonetti' (IMGC, 1994) and at the Institute for Scientific Instruments (ISI, 1996). Comparative results regarding frequency difference, repeatability and stability are presented. Results proved a good reproducibility of the performances during the time.","PeriodicalId":383583,"journal":{"name":"ROMOPTO International Conference on Micro- to Nano- Photonics III","volume":"87 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":"133029722","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. Crunteanu, R. Alexandrescu, R. Cireasa, Ş. Cojocaru, I. Morjan, A. Andrei, Ashock Kumar
Since the theoretical studies of Liu and Cohen who predicted the existence of a superhard phase of carbon nitride, a great deal of effort was underdone in order to synthesize this hypothetical material with a nitrogen content as high as the 57% present in a (beta) -C3N4 structure. This study presents an attempt to produce CNx thin films using the laser-induced CVD technique. CW CO2 laser was used for irradiating various carbon-nitrogen containing mixtures such as C2H4/N2O/NH3. The CNx films were grown alternatively on bare alumina ((alpha) - Al2O3) substrates and on pre-deposited Ti films. A comparative analysis of nitrogen incorporation in the films obtained in different experimental conditions was performed by means of the X-ray photoelectron spectroscopy. The same method was used to identify the chemical states of the CN system.
{"title":"Deposition of carbon nitride thin films by IR-laser-induced reactions in carbon-nitrogen gas-phase compounds","authors":"A. Crunteanu, R. Alexandrescu, R. Cireasa, Ş. Cojocaru, I. Morjan, A. Andrei, Ashock Kumar","doi":"10.1117/12.312751","DOIUrl":"https://doi.org/10.1117/12.312751","url":null,"abstract":"Since the theoretical studies of Liu and Cohen who predicted the existence of a superhard phase of carbon nitride, a great deal of effort was underdone in order to synthesize this hypothetical material with a nitrogen content as high as the 57% present in a (beta) -C3N4 structure. This study presents an attempt to produce CNx thin films using the laser-induced CVD technique. CW CO2 laser was used for irradiating various carbon-nitrogen containing mixtures such as C2H4/N2O/NH3. The CNx films were grown alternatively on bare alumina ((alpha) - Al2O3) substrates and on pre-deposited Ti films. A comparative analysis of nitrogen incorporation in the films obtained in different experimental conditions was performed by means of the X-ray photoelectron spectroscopy. The same method was used to identify the chemical states of the CN system.","PeriodicalId":383583,"journal":{"name":"ROMOPTO International Conference on Micro- to Nano- Photonics III","volume":"10 5 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":"116078507","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 we study the light scattering on the different mesophases of TBBA-CM mixture. We used He-Ne laser radiation and we derived a simple theoretical model of the diffusion process. The results are in good agreement with the data provided by other experimental methods.
{"title":"Light scattering in liquid crystals","authors":"M. Ursache, M. Socaciu, C. Sarpe-Tudoran","doi":"10.1117/12.312713","DOIUrl":"https://doi.org/10.1117/12.312713","url":null,"abstract":"In this paper we study the light scattering on the different mesophases of TBBA-CM mixture. We used He-Ne laser radiation and we derived a simple theoretical model of the diffusion process. The results are in good agreement with the data provided by other experimental methods.","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":"116222206","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. Frandas, D. Dadarlat, M. Chirtoc, H. Jalink, D. Bićanić, D. Paris, Jean S. Antoniow, M. Egee, C. Ungureanu
The photopyroelectric method in different experimental configurations was used for thermophysical characterization of agricultural and biological samples. The study appears important due to the relation of thermal parameters to the quality of foodstuffs (connected to their preservation, storage and adulteration), migration profiles in biodegradable packages, and the mechanism of desiccation tolerance of seeds. Results are presented on the thermal parameters measurement and their dependence on temperature and water content for samples such as: honey, starch, seeds.
{"title":"Photothermal method using a pyroelectric sensor for thermophysical characterization of agricultural and biological samples","authors":"A. Frandas, D. Dadarlat, M. Chirtoc, H. Jalink, D. Bićanić, D. Paris, Jean S. Antoniow, M. Egee, C. Ungureanu","doi":"10.1117/12.312710","DOIUrl":"https://doi.org/10.1117/12.312710","url":null,"abstract":"The photopyroelectric method in different experimental configurations was used for thermophysical characterization of agricultural and biological samples. The study appears important due to the relation of thermal parameters to the quality of foodstuffs (connected to their preservation, storage and adulteration), migration profiles in biodegradable packages, and the mechanism of desiccation tolerance of seeds. Results are presented on the thermal parameters measurement and their dependence on temperature and water content for samples such as: honey, starch, seeds.","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":"126160128","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 order to describe the transversal mode construction in a real laser resonator, a mathematical model was investigated. The analysis use Kirchhoff-Fresnel diffraction equation and amplification processes in the active medium, that was supposed as sum of thin discs with gain and losses constants on every disc's length. Influence of additional phenomenon on laser beam characteristics, as phase-shift caused by active medium thermal induced refractive power and curvature of the resonator mirrors were considered.
{"title":"Influence of active-medium properties on high-power solid state laser beam characteristics","authors":"N. Pavel, T. Taira, T. Dascălu, V. Lupei","doi":"10.1117/12.312659","DOIUrl":"https://doi.org/10.1117/12.312659","url":null,"abstract":"In order to describe the transversal mode construction in a real laser resonator, a mathematical model was investigated. The analysis use Kirchhoff-Fresnel diffraction equation and amplification processes in the active medium, that was supposed as sum of thin discs with gain and losses constants on every disc's length. Influence of additional phenomenon on laser beam characteristics, as phase-shift caused by active medium thermal induced refractive power and curvature of the resonator mirrors were considered.","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":"127386437","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 introduce a theoretical model to describe all the phenomena implied in the interaction process between the high intensity UV laser radiation and a solid target in the ambience of a low- pressure chemically active gas. The action of the laser radiation upon the solid surface is simulated by solving the 1D heat equation. A hydrodynamical 1D model was further applied to describe the interaction between the laser radiation and the plasma expanding in front of the target. The absorption of the laser radiation in the vapor plasma could be considered with the aid of a multifluid model. The transit of the ablated atoms and/or of the new formed chemical compound was approached with a Monte-Carlo method. We could compute time and space distribution of the main plasma parameters (e.g. the plasma density and temperature). We could finally predict the thickness distribution of a film deposited on a collector placed parallel to the target at a distance of (1.5 - 3) cm range. The calculus was conducted for the case of a Ti target in low pressure nitrogen.
{"title":"Theoretical model for the reactive pulsed deposition process: application to the case of ablation of a Ti target in low-pressure N2","authors":"J. Neamțu, I. Mihăilescu","doi":"10.1117/12.312771","DOIUrl":"https://doi.org/10.1117/12.312771","url":null,"abstract":"We introduce a theoretical model to describe all the phenomena implied in the interaction process between the high intensity UV laser radiation and a solid target in the ambience of a low- pressure chemically active gas. The action of the laser radiation upon the solid surface is simulated by solving the 1D heat equation. A hydrodynamical 1D model was further applied to describe the interaction between the laser radiation and the plasma expanding in front of the target. The absorption of the laser radiation in the vapor plasma could be considered with the aid of a multifluid model. The transit of the ablated atoms and/or of the new formed chemical compound was approached with a Monte-Carlo method. We could compute time and space distribution of the main plasma parameters (e.g. the plasma density and temperature). We could finally predict the thickness distribution of a film deposited on a collector placed parallel to the target at a distance of (1.5 - 3) cm range. The calculus was conducted for the case of a Ti target in low pressure nitrogen.","PeriodicalId":383583,"journal":{"name":"ROMOPTO International Conference on Micro- to Nano- Photonics III","volume":"3 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":"127815603","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}
Several image encryption methods have been recently considered. This paper presents a new image enciphering method starting from the mixing transformations suggested by C.E. Shannon for natural language. There are two ways in which images are involved here: first, as a means of visual perception of the mixing transformation features (the very sophisticated diffusion and confusion); secondly, as the application field itself. Both the theoretical and experimental aspects pointed out here show the high quality of this method of image enciphering. The method illustrates were made either for simulated images with different probability laws and autocorrelation functions, or for natural images.
{"title":"Cryptographic mixing transformations for image applications","authors":"A. Vlad, M. Mitrea","doi":"10.1117/12.312794","DOIUrl":"https://doi.org/10.1117/12.312794","url":null,"abstract":"Several image encryption methods have been recently considered. This paper presents a new image enciphering method starting from the mixing transformations suggested by C.E. Shannon for natural language. There are two ways in which images are involved here: first, as a means of visual perception of the mixing transformation features (the very sophisticated diffusion and confusion); secondly, as the application field itself. Both the theoretical and experimental aspects pointed out here show the high quality of this method of image enciphering. The method illustrates were made either for simulated images with different probability laws and autocorrelation functions, or for natural images.","PeriodicalId":383583,"journal":{"name":"ROMOPTO International Conference on Micro- to Nano- Photonics III","volume":"18 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":"126304708","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}
High power pulsed laser diodes are of interest due to their potential use in medicine and peculiar applications. This paper presents failure analysis for catastrophic damage in GaAs/AlGaAs LOC pulsed laser devices. There is presented failure decrease of optical power as 1 g (P/P0) equals f(t) where P0 is initial power, P actual power, t-operating time. The damaged devices were investigated by optical and scanning electron microscopy and there was performed a electron dispersion spectroscopy analysis. These experiments advanced the idea of dividing catastrophic degradation in three types, respectively: 1-catastrophic optical mirror damage, 2-catastrophic damage due to major mechanic defects, 3-catastrophic damage due to metal migration (e.g. Au). There was established an experimental criterion to characterize catastrophic damage.
{"title":"Degradation effects in pulsed AlGaAs large optical cavity (LOC) structure laser diodes","authors":"R. Ghiţă, E. Vasile, V. Cimpoca, N. Bǎlţǎţeanu","doi":"10.1117/12.312670","DOIUrl":"https://doi.org/10.1117/12.312670","url":null,"abstract":"High power pulsed laser diodes are of interest due to their potential use in medicine and peculiar applications. This paper presents failure analysis for catastrophic damage in GaAs/AlGaAs LOC pulsed laser devices. There is presented failure decrease of optical power as 1 g (P/P0) equals f(t) where P0 is initial power, P actual power, t-operating time. The damaged devices were investigated by optical and scanning electron microscopy and there was performed a electron dispersion spectroscopy analysis. These experiments advanced the idea of dividing catastrophic degradation in three types, respectively: 1-catastrophic optical mirror damage, 2-catastrophic damage due to major mechanic defects, 3-catastrophic damage due to metal migration (e.g. Au). There was established an experimental criterion to characterize catastrophic damage.","PeriodicalId":383583,"journal":{"name":"ROMOPTO International Conference on Micro- to Nano- Photonics III","volume":"5 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":"127602254","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 sensitization with Yb3+ of other rare earth ions emission is intensively used in the last years for increasing excitation efficiency of infrared (diode laser) pumped solid state lasers. It proved as a good sensitizer for Pr3+ emission in various matrices. The spectral investigations for the elucidation of the nature of multisite structure of Pr3+ in YAG and of the Yb3+ co-doping on Pr3+:YAG are presented in this paper. In Pr3+:YAG two types of multisites have been observed: perturbed Pr3+ sites by nonstoichiometric defects and strongly coupled Pr3+ - Pr3+ near neighbor pairs. Pr3+ spectra in Yb3+, Pr3+:YAG show new lines assigned to near neighbor Pr3+ - Yb3+ pairs and Pr3+ - Yb3+ - Yb3+ triads.
{"title":"Spectroscopy of Yb3+codoped Pr3+:YAG laser crystals","authors":"A. Lupei, V. Lupei, A. Petraru","doi":"10.1117/12.312808","DOIUrl":"https://doi.org/10.1117/12.312808","url":null,"abstract":"The sensitization with Yb3+ of other rare earth ions emission is intensively used in the last years for increasing excitation efficiency of infrared (diode laser) pumped solid state lasers. It proved as a good sensitizer for Pr3+ emission in various matrices. The spectral investigations for the elucidation of the nature of multisite structure of Pr3+ in YAG and of the Yb3+ co-doping on Pr3+:YAG are presented in this paper. In Pr3+:YAG two types of multisites have been observed: perturbed Pr3+ sites by nonstoichiometric defects and strongly coupled Pr3+ - Pr3+ near neighbor pairs. Pr3+ spectra in Yb3+, Pr3+:YAG show new lines assigned to near neighbor Pr3+ - Yb3+ pairs and Pr3+ - Yb3+ - Yb3+ triads.","PeriodicalId":383583,"journal":{"name":"ROMOPTO International Conference on Micro- to Nano- Photonics III","volume":"37 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":"127882424","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 analyzing the polarization spectral structure of the time- varying spinorial fields obtained by light modulation, the notions of spectral Jones vector and spectral coherence matrix are introduced. The KDP longitudinal electrooptic modulator is presented as an example.
{"title":"Spectral Jones vectors and spectral coherence matrices in analyzing modulated light","authors":"T. Tudor, I. Vinkler","doi":"10.1117/12.312800","DOIUrl":"https://doi.org/10.1117/12.312800","url":null,"abstract":"In analyzing the polarization spectral structure of the time- varying spinorial fields obtained by light modulation, the notions of spectral Jones vector and spectral coherence matrix are introduced. The KDP longitudinal electrooptic modulator is presented as an example.","PeriodicalId":383583,"journal":{"name":"ROMOPTO International Conference on Micro- to Nano- Photonics III","volume":"12 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":"127923915","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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