V. Damian, M. Bojan, A. Sima, D. Cristea, A. Dinescu, R. Muller
In this paper we describe a traceable to the meter standard method to measure the height of an artifact used as a calibrator for observation instruments in nanotechnologies and nanosciences. The artifact is a grating specially manufactured so that its features (height, pitch, width, wall angles) are highly uniform across its area. A Linnik microscope designed for longitudinal (vertical) measurements using the principle of white light interferometry was used to determine the height of the grating. To insure the traceability of the measurements a laser source of known wavelength was used and the measurements obtained using white light were calibrated to it. The experimental data was statistically analyzed and the measurement precision was estimated to be in the range of nanometers. The data were compared with the results obtained using the TIC method with a Carl Zeiss microscope.
{"title":"White light interferometry for vertical artifact calibration","authors":"V. Damian, M. Bojan, A. Sima, D. Cristea, A. Dinescu, R. Muller","doi":"10.1117/12.801969","DOIUrl":"https://doi.org/10.1117/12.801969","url":null,"abstract":"In this paper we describe a traceable to the meter standard method to measure the height of an artifact used as a calibrator for observation instruments in nanotechnologies and nanosciences. The artifact is a grating specially manufactured so that its features (height, pitch, width, wall angles) are highly uniform across its area. A Linnik microscope designed for longitudinal (vertical) measurements using the principle of white light interferometry was used to determine the height of the grating. To insure the traceability of the measurements a laser source of known wavelength was used and the measurements obtained using white light were calibrated to it. The experimental data was statistically analyzed and the measurement precision was estimated to be in the range of nanometers. The data were compared with the results obtained using the TIC method with a Carl Zeiss microscope.","PeriodicalId":390439,"journal":{"name":"Industrial Laser Applications: INDLAS","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2008-03-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"120861120","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}
Due to the peculiar energy level scheme of Er3+, with many energetic resonances, Er-doped crystals can generate laser radiations in various wavelength domains: at 3 µm with applications in medicine and biology, at 1.5 μm (for telecommunications) and in visible (green) with potential applications in medicine. Low concentrated Er-doped crystals are suitable for 1.5 μm and green (upconversion pumped) lasers while high concentrated ones - for 3 μm emission. In this paper we discuss the possibilities and the limits of the lasers based on erbium-doped crystals using rate equations models.
{"title":"Infrared and visible laser transitions in erbium-doped crystals","authors":"S. Georgescu, O. Toma","doi":"10.1117/12.801933","DOIUrl":"https://doi.org/10.1117/12.801933","url":null,"abstract":"Due to the peculiar energy level scheme of Er3+, with many energetic resonances, Er-doped crystals can generate laser radiations in various wavelength domains: at 3 µm with applications in medicine and biology, at 1.5 μm (for telecommunications) and in visible (green) with potential applications in medicine. Low concentrated Er-doped crystals are suitable for 1.5 μm and green (upconversion pumped) lasers while high concentrated ones - for 3 μm emission. In this paper we discuss the possibilities and the limits of the lasers based on erbium-doped crystals using rate equations models.","PeriodicalId":390439,"journal":{"name":"Industrial Laser Applications: INDLAS","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2008-03-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133997856","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 paper contains a survey of the problems commonly encountered by anyone attempting to accurately determine or specify the speed of fast photodetectors, in the bandwidth range: hundreds of MHz - tens of GHz. Two techniques are presented: one determining the minimum duration of the optical pulses which can be "seen" accurately enough, and the other determining the electrical (power) spectrum of the photodetector, leading to bandwidth determination. Experimental determination of the bandwidth for two fast photodiodes is presented, using the latter technique.
{"title":"Determination of the speed / banwidth for fast photodetectors using picosecond lasers","authors":"E. Smeu","doi":"10.1117/12.801960","DOIUrl":"https://doi.org/10.1117/12.801960","url":null,"abstract":"The paper contains a survey of the problems commonly encountered by anyone attempting to accurately determine or specify the speed of fast photodetectors, in the bandwidth range: hundreds of MHz - tens of GHz. Two techniques are presented: one determining the minimum duration of the optical pulses which can be \"seen\" accurately enough, and the other determining the electrical (power) spectrum of the photodetector, leading to bandwidth determination. Experimental determination of the bandwidth for two fast photodiodes is presented, using the latter technique.","PeriodicalId":390439,"journal":{"name":"Industrial Laser Applications: INDLAS","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2008-03-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131019122","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 developed all-solid-state continuous-wave diode end-pumped Nd:YAG and Nd:GdVO4 lasers that were passively Q-switched by Cr4+:YAG saturable absorbers. The Nd:YAG laser delivered laser pulses with 138 mJ maximum energy and duration of 42 ns, with 3.3 W average power at 1.06 mm for 13.3 W of pump power at 807 nm. An average power at 1.06 mm of 1.4 W was obtained from Nd:GdVO4 under pumping with 7.2 W power at 808 nm. The pulse energy and the pulse duration were 41 mJ and 40 ns, respectively, which correspond to 1 kW pulse peak power. The laser pulses characteristics are discussed for Cr4+:YAG saturable absorbers with different values of the initial transmission.
{"title":"Continuous-wave diode end-pumped Nd: YAG and Nd:GdVO4 lasers passively Q-switched by Cr4+: YAG saturable absorbers","authors":"C. Petre, N. Vasile, N. Pavel, T. Dascălu","doi":"10.1117/12.802022","DOIUrl":"https://doi.org/10.1117/12.802022","url":null,"abstract":"We have developed all-solid-state continuous-wave diode end-pumped Nd:YAG and Nd:GdVO4 lasers that were passively Q-switched by Cr4+:YAG saturable absorbers. The Nd:YAG laser delivered laser pulses with 138 mJ maximum energy and duration of 42 ns, with 3.3 W average power at 1.06 mm for 13.3 W of pump power at 807 nm. An average power at 1.06 mm of 1.4 W was obtained from Nd:GdVO4 under pumping with 7.2 W power at 808 nm. The pulse energy and the pulse duration were 41 mJ and 40 ns, respectively, which correspond to 1 kW pulse peak power. The laser pulses characteristics are discussed for Cr4+:YAG saturable absorbers with different values of the initial transmission.","PeriodicalId":390439,"journal":{"name":"Industrial Laser Applications: INDLAS","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2008-03-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127472221","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}
When coherent light is incident upon an optically thick biological fluid having scattering centers (SC) in suspension, like whole blood, the backscattered light can be recorded, resulting an image speckle. A program was written to extract the time series from each pixel of the CDD conversion matrix. The autocorrelation time of the series was calculated and the autocorrelation time was determined on blood samples from different human subjects. The autocorrelation time was analyzed and compared with the erythrocyte sedimentation rate (ESR) measured during a standard laboratory test using the modified Westergren method. A different procedure to record the time series, using a detector and a data acquisition system was used as well and the autocorrelation time was calculated for the time series recorded using this procedure. The results of the work performed so far indicate that the two properties appear to be slightly correlated. A fast procedure for assessing the ESR is suggested.
{"title":"Application of whole blood image speckle analysis","authors":"D. Chicea","doi":"10.1117/12.801934","DOIUrl":"https://doi.org/10.1117/12.801934","url":null,"abstract":"When coherent light is incident upon an optically thick biological fluid having scattering centers (SC) in suspension, like whole blood, the backscattered light can be recorded, resulting an image speckle. A program was written to extract the time series from each pixel of the CDD conversion matrix. The autocorrelation time of the series was calculated and the autocorrelation time was determined on blood samples from different human subjects. The autocorrelation time was analyzed and compared with the erythrocyte sedimentation rate (ESR) measured during a standard laboratory test using the modified Westergren method. A different procedure to record the time series, using a detector and a data acquisition system was used as well and the autocorrelation time was calculated for the time series recorded using this procedure. The results of the work performed so far indicate that the two properties appear to be slightly correlated. A fast procedure for assessing the ESR is suggested.","PeriodicalId":390439,"journal":{"name":"Industrial Laser Applications: INDLAS","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2008-03-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128621064","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 microstructure of the weld and the extent to which it is different from the thermo-mechanically processed base material is strongly influenced by the thermal cycle of welding. The mechanical properties of composite weld structures in titanium alloys depend on structural characteristics of each region (weld, base material and heat affected area), influenced by the specific thermal cycle imposed during welding and the subsequent post-weld heat treatment. In order to improve the as-welded metal toughness and ductility, the welded metal was subjected to various post weld laser heat treatments, above and below beta transus temperature in a shielding atmosphere of pure argon. Standard micro-hardness measurements and tensile strength techniques showed higher mechanical properties of the heat treated samples in different conditions with respect to the base metal. Metallographic investigations attribute this to the formation of α'phases in heat treated material, especially in the weld metal.
{"title":"Effects of the laser beam superficial heat treatment on the gas Tungsten arc Ti-6al-4v welded metal microstructure","authors":"I. Voiculescu, O. Donţu, V. Geantǎ, S. Ganatsios","doi":"10.1117/12.801972","DOIUrl":"https://doi.org/10.1117/12.801972","url":null,"abstract":"The microstructure of the weld and the extent to which it is different from the thermo-mechanically processed base material is strongly influenced by the thermal cycle of welding. The mechanical properties of composite weld structures in titanium alloys depend on structural characteristics of each region (weld, base material and heat affected area), influenced by the specific thermal cycle imposed during welding and the subsequent post-weld heat treatment. In order to improve the as-welded metal toughness and ductility, the welded metal was subjected to various post weld laser heat treatments, above and below beta transus temperature in a shielding atmosphere of pure argon. Standard micro-hardness measurements and tensile strength techniques showed higher mechanical properties of the heat treated samples in different conditions with respect to the base metal. Metallographic investigations attribute this to the formation of α'phases in heat treated material, especially in the weld metal.","PeriodicalId":390439,"journal":{"name":"Industrial Laser Applications: INDLAS","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2008-03-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126169667","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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