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Wyświetlanie 1-15 z 18
Tytuł:
Theory of Ultrafast Demagnetization after Femtosecond Laser Pulses
Autorzy:
Fähnle, M.
Illg, Ch.
Haag, M.
Teeny, N.
Powiązania:
https://bibliotekanauki.pl/articles/1384049.pdf
Data publikacji:
2015-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.78.Jp
75.30.Ds
75.40.Gb
Opis:
Experimentally it has been found that a ferromagnetic metallic film is strongly demagnetized within few hundred fs after exposure to a fs laser pulse. The theories of this ultrafast demagnetization are reviewed, especially the influence of scatterings of the excited electrons at phonons and at magnons. The calculations for phonons and magnons are performed by the ab initio spin-density-functional electron theory for Ni and Fe, and they are based on Fermi's golden rule for transition rates. The application of this rule on the fs time scale is critically discussed in view of results from quantum-kinetic density-matrix calculations. It is shown that the experimentally observed demagnetization rates cannot be explained by spin-flip scatterings of electrons exclusively at phonons or exclusively at magnons. A combination of individual spin-flip electron-phonon and spin-flip electron-magnon processes is shown to be a potential candidate for the explanation of ultrafast demagnetization.
Źródło:
Acta Physica Polonica A; 2015, 127, 2; 170-175
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Adaptive Optical Delay Lines for Femtosecond Laser Pulses Shaping
Autorzy:
Molchanov, V.
Chizhikov, S.
Makarov, O.
Solodovnikov, N.
Ginzburg, V.
Katin, E.
Khazanov, E.
Lozhkarev, V.
Yakovlev, I.
Epatko, I.
Serov, R.
Powiązania:
https://bibliotekanauki.pl/articles/1807737.pdf
Data publikacji:
2009-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
42.65.Re
42.79.Jq
43.38.Zp
Opis:
The paper is devoted to investigation of adaptive optical delay lines, intended for femtosecond pulse shaping. Experiments were performed in the sub PW laser system, based on optical parametrical chirped pulse amplification. The experimental device has revealed high spectral resolution (0.6 nm at 1250 nm) high efficiency, (70% over a 120 nm spectral width at 1250 nm) and flexibility of seed pulse amplitude control. Proper shaping of the transmission function of adaptive optical delay line allows to double the femtosecond pulse spectrum band width.
Źródło:
Acta Physica Polonica A; 2009, 116, 3; 355-358
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Dispersive Controlling of Femtosecond Laser Radiation: New Opportunities and Developments
Autorzy:
Molchanov, V.
Yushkov, K.
Powiązania:
https://bibliotekanauki.pl/articles/1377941.pdf
Data publikacji:
2015-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
42.60.By
42.79.Jq
Opis:
The paper is devoted to new trends in dispersive control techniques for ultrafast light emission. Acoustooptical dispersive delay lines for controlling the spectral components and phase composition of ultrashort laser pulses are considered. The method of super high frequency modulation of chirped femtosecond laser pulses is proposed. Theoretical approach to dispersive pulse shaping is supported by the experiments.
Źródło:
Acta Physica Polonica A; 2015, 127, 1; 20-24
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Terahertz Emission from Narrow Gap Semiconductors Photoexcited by Femtosecond Laser Pulses
Autorzy:
Adomavičius, R.
Urbanowicz, A.
Molis, G.
Krotkus, A.
Powiązania:
https://bibliotekanauki.pl/articles/2041649.pdf
Data publikacji:
2005-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
42.65.Re
07.57.Hm
78.47.+p
72.30.+q
Opis:
Large increase in the emitted terahertz power was observed for p-InAs samples with the p-doping levels of approximately 10$\text{}^{16}$-10$\text{}^{17}$ cm$\text{}^{-3}$. This increase was explained by a large surface depletion layer and an electric-field-induced optical rectification effect in the layer. Terahertz fields radiated by the samples of all three investigated Cd$\text{}_{x}$Hg$\text{}_{1-x}$Te layers was of the same order of magnitude. No azimuthal angle dependence of the radiated signal was detected, which evidences that linear current surge effect is dominating over nonlinear optical rectification. Azimuthal angle and magnetic fields emission witness that it is caused by linear photo-Dember type processes.
Źródło:
Acta Physica Polonica A; 2005, 107, 1; 132-136
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Microstructure Changes of Nickel-Base Superalloys Induced by Interaction with Femtosecond Laser Beam
Autorzy:
Petronic, S.
Drecun-Nesic, S.
Milosavljevic, A.
Sedmak, A.
Popovic, M.
Kovacevic, A.
Powiązania:
https://bibliotekanauki.pl/articles/1791235.pdf
Data publikacji:
2009-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
01.55.+b
42.62.-b
81.05.Bx
Opis:
The investigation was performed on nickel-base superalloys, with nickel being the most influential alloying ingredient. After thermo-mechanical preparation and corresponding processing, femtosecond laser beam machining has been performed. The laser wavelength was 800 nm. The exposition time, during which the samples have been exposed to the pulses of femtosecond laser beam varied, as well as the average output power. The changes of both the output power and the exposition time enabled the samples to be irradiated with different total energy during each exposition. The changes in samples microstructure were observed with optical and scanning electron microscopy, with energy-dispersive spectrometry, and analyzed as well. Microhardness measurements of both base material and ablated spots have been performed.
Źródło:
Acta Physica Polonica A; 2009, 116, 4; 550-552
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Bleaching and Darkening Effect in Photochromic Glasses under Irradiation with Femtosecond Laser Pulses
Autorzy:
Jamshidi-Ghaleh, K.
Powiązania:
https://bibliotekanauki.pl/articles/1791201.pdf
Data publikacji:
2009-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
33.80.Wz
78.20.Ci
Opis:
In this paper, the photochromic oxide glass sample under interaction of 200 fs laser pulses at 800 nm wavelength is studied. Two types of laser-induced modifications, bleaching and darkening, are observed. The induced darkening is observed inside the bleached volume. The effect of incident laser shot number and pulse energy on the bleached and darkened area are investigated. The pulse energy accumulation model is applied to investigation of both bleached and darkened area sizes. The bleaching and darkening modification fluence threshold are determined for single and multi-shot laser pulses.
Źródło:
Acta Physica Polonica A; 2009, 116, 4; 501-503
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
New pico- and femtosecond laser based sources: from the Infra-Red to the XUV
Autorzy:
Petite, G.
Powiązania:
https://bibliotekanauki.pl/articles/308713.pdf
Data publikacji:
2000
Wydawca:
Instytut Łączności - Państwowy Instytut Badawczy
Tematy:
lasers
short pulses
ultrafast phenomena
Opis:
In this paper, we review a number of recent developments concerning laser or laser-based sources generating pico- or subpicosecond pulses of light at wavelengths now ranging from the mid Infra-Red (50 ľm) to the XUV (11,9 nm). Those include the new generation of 'Chirp Pulse Amplification' laser systems, Free Electron Lasers operating in the IR or visible range, and a number of laser driven sources covering the XUV range, and a number of laser driven sources covering the XUV range, generally based on the high intensity irradiation of solid or gaseous targets. The main perspectives, applications and essential issues concerning such sources are discussed.
Źródło:
Journal of Telecommunications and Information Technology; 2000, 1-2; 6-15
1509-4553
1899-8852
Pojawia się w:
Journal of Telecommunications and Information Technology
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Far-Infrared Few-Cycle-Pulse Generation in Quantum-Well Heterostructures under Femtosecond Laser Pumping
Autorzy:
Belyanin, A. A.
Kocharovsky, V. V.
Kocharovsky, Vl. V.
Pestov, D. S.
Scully, M. O.
Powiązania:
https://bibliotekanauki.pl/articles/2041669.pdf
Data publikacji:
2005-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
42.55.Px
42.60.-v
Opis:
It is shown that the resonant nonlinear-wave mixing in the semiconductor quantum wells under a femtosecond optical pulse excitation can be used for the generation of the utmost short mid/far-infrared pulses with a few- or even single-cycle duration defined by pump duration.
Źródło:
Acta Physica Polonica A; 2005, 107, 1; 151-157
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Fine-Scale Structure Investigation of Nimonic 263 Superalloy Surface Damaged by Femtosecond Laser Beam
Autorzy:
Milosavljevic, A.
Petronic, S.
Sreckovic, M.
Kovacevic, A.
Krmpot, A.
Kovacevic, K.
Powiązania:
https://bibliotekanauki.pl/articles/1791236.pdf
Data publikacji:
2009-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
01.55.+b
42.62.-b
81.05.Bx
81.20.Vj
Opis:
Due to the specific conditions of manufacturing, processing and utilization of nickel-base superalloys, the implementation of contemporary precision techniques is necessary in the research of the alloys features. Multi-component nickel-base superalloys, with about of 50% of nickel content, are commonly exploited in the conditions of high temperatures and pressures as well as in various aggressive operating environments. For successful quality control, which includes the monitoring of the changes in the alloy microstructure, fine-scale structure investigations are necessary. In this work, the samples of nickel-base superalloys have been exposed to 800 nm femtosecond laser in various operating regimes. Surface damages and dents caused by femtosecond laser pulses have been observed by optical and scanning microscopy.
Źródło:
Acta Physica Polonica A; 2009, 116, 4; 553-556
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The application of the femtosecond laser in cataract surgery
Zastosowanie lasera femtosekundowego w operacji zaćmy
Autorzy:
Kanclerz, Piotr
Pluta, Karolina
Powiązania:
https://bibliotekanauki.pl/articles/2040440.pdf
Data publikacji:
2021-05-25
Wydawca:
Medical Education
Tematy:
cataract surgery
femtosecond laser-assisted cataract surgery
phacoemulsification
operacja zaćmy
laser femtosekundowy
fakoemulsyfikacja
Opis:
Introduction: Since the introduction, femtosecond laser-assisted cataract surgery (FLACS) was believed to revolutionize cataract surgery. However, the judgment of clinical benefits was found to be far more complex than initially might have been thought. The aim of this review was to analyze the benefits and drawbacks of FLACS compared to traditional phacoemulsification cataract surgery. Results: The benefits of FLACS include lower cumulated phacoemulsification time and endothelial cell loss, perfect centration of the capsulotomy, and the possibility to perform precise femtosecond-assisted arcuate keratotomy incisions. The major disadvantages of FLACS are: high cost of the laser and the disposables for surgery, FLACS-specific intraoperative capsular complications, as well as the risk of intraoperative miosis and the learning curve. Conclusions: FLACS seems to be beneficial in some groups of patients i.e., with low baseline endothelial cell count, or those planning to receive multifocal intraocular lenses. Nevertheless, having considered that the advantages of FLACS might not be clear in every routine case, it cannot be considered as cost-effective.
Wstęp: Oczekiwano, że wprowadzenie laserów femtosekundowych do chirurgii zaćmy zrewolucjonizuje tę gałąź okulistyki. Jednak ocena korzyści klinicznych okazała się znacznie bardziej złożona, niż można było pierwotnie przypuszczać. Celem niniejszej pracy był przegląd korzyści i wad operacji zaćmy wykonanej z wykorzystaniem lasera femtosekundowego w porównaniu z tradycyjną metodą fakoemulsyfikacji. Wyniki: Korzyści związane z użyciem lasera femtosekundowego w operacji zaćmy obejmują niższy skumulowany czas fakoemulsyfikacji, zmniejszenie utraty komórek śródbłonka rogówki, idealną centrację lasera oraz możliwość jednoczesnego wykonania łukowatej keratotomii. Głównymi wadami są: wysoki koszt lasera i materiałów jednorazowych, specyficzne dla operacji zaćmy z użyciem lasera femtosekundowego torebkowe powikłania śródoperacyjne, a także ryzyko śródoperacyjnego zwężenia źrenicy. Wnioski: Operację zaćmy z zastosowaniem lasera femtosekundowego można uznać za korzystną metodę w niektórych grupach pacjentów: u tych z niską wyjściową liczbą komórek śródbłonka lub u tych, u których planuje się użyć wieloogniskowych soczewek wewnątrzgałkowych. Niemniej jednak zalety nie są ewidentne w każdym przypadku, a metody tej nie można uznać za opłacalną ekonomicznie.
Źródło:
OphthaTherapy; 2021, 8, 2; 125-130
2353-7175
2543-9987
Pojawia się w:
OphthaTherapy
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Terahertz Generation from Femtosecond-Laser-Excited GaAs Surface Due to Electric-Field-Induced, Optical Rectification
Autorzy:
Malevich, V.
Ziaziulia, P.
Manak, I.
Powiązania:
https://bibliotekanauki.pl/articles/1813211.pdf
Data publikacji:
2008-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
42.65.Re
42.65.Ky
73.30.+y
Opis:
The dynamics of the depletion field screening induced by photoexcited carriers and THz generation caused by the electric-field-induced optical rectification are simulated for GaAs surface excited by femtosecond laser radiation on the basis of an ensemble Monte Carlo method. The results show that the photocarrier-induced screening occurs on a subpicosecond time scale and THz pulse essentially changes its wave form depending on excitation pulse duration and fluence. The possibility to use the depletion electric field induced THz generation for study of subpicosecond electric field screening dynamics is discussed.
Źródło:
Acta Physica Polonica A; 2008, 113, 3; 887-890
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Numerical simulations of generation of high-energy ion beams driven by a petawatt femtosecond laser
Autorzy:
Domański, J
Badziak, J.
Jabłoński, S.
Powiązania:
https://bibliotekanauki.pl/articles/146458.pdf
Data publikacji:
2015
Wydawca:
Instytut Chemii i Techniki Jądrowej
Tematy:
laser acceleration
laser plasma
ions
particle-in-cell simulations
Opis:
This contribution presents results of a Particle-in-Cell simulation of ion beam acceleration via the interaction of a petawatt 25 fs laser pulse of high intensity (up to ~1021 W/cm2) with thin hydrocarbon (CH) and erbium hydride (ErH3) targets of equal areal mass density (of 0.6 g/m2). A special attention is paid to the effect that the laser pulse polarization and the material composition of the target have on the maximum ion energies and the number of high energy (>10 MeV) protons. It is shown that both the mean and the maximum ion energies are higher for the linear polarization than for the circular one. A comparison of the maximum proton energies and the total number of protons generated from the CH and ErH3 targets using a linearly polarized beam is presented. For the ErH3 targets the maximum proton energies are higher and they reach 50 MeV for the laser pulse intensity of 1021 W/cm2. The number of protons with energies higher than 10 MeV is an order of magnitude higher for the ErH3 targets than that for the CH targets.
Źródło:
Nukleonika; 2015, 60, 2; 229-232
0029-5922
1508-5791
Pojawia się w:
Nukleonika
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Nonlinear Responses and Optical Properties Modification οf SK3 under Irradiation of Femtosecond Laser Pulses
Autorzy:
Jamshidi-Ghaleh, K.
Rezapour, H.
Powiązania:
https://bibliotekanauki.pl/articles/1795599.pdf
Data publikacji:
2009-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
33.80.Wz
78.20.Ci
Opis:
In this paper, the nonlinear responses and optical properties modification in SK3 glass sample are investigated. The nonlinear responses measurements were performed by using of nonlinear transmission monitoring of 200 fs at 800 nm laser pulses. The optical power limiting threshold of the sample is measured to be about 40 mJ/$cm^{2}$. The decrease of transmitted intensity is about 63% compared to the theoretical linear transmission at 270 mJ/$cm^{2}$ incident pulse energy. For prediction of the experimental nonlinear behavior results, a theoretical model based on three-photon absorption and absorption of free carriers is presented. By fitting of experimental data with theoretical model, three-photon absorption coefficient and free-carrier absorption cross-section are reported. The photo-induced optical properties modification of the SK3 sample is investigated also. The modifications that appear as darkening are observed below breakdown threshold intensity. To analyses of modified region sizes, the laser pulse energy accumulation model is applied.
Źródło:
Acta Physica Polonica A; 2009, 116, 4; 588-591
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Study of structure and morphology of surface layers formed on TRIP steel by the femtosecond laser treatment
Autorzy:
Duriagina, Z. A.
Tepla, T. L.
Kulyk, V. V.
Kosarevych, R. Ya.
Vira, V. V.
Semeniuk, O. A.
Powiązania:
https://bibliotekanauki.pl/articles/367952.pdf
Data publikacji:
2019
Wydawca:
Stowarzyszenie Komputerowej Nauki o Materiałach i Inżynierii Powierzchni w Gliwicach
Tematy:
femtosecond laser
TRIP steel (03X13AG19)
image processing algorithms
digital image analysis
metallographic complex
laser femtosekundowy
stal TRIP
algorytmy przetwarzania obrazu
cyfrowa analiza obrazu
Opis:
Purpose: The purpose of the work is to demonstrate the possibility of using a femtosecond laser for forming surface layers with an adjustable microstructure on the surface of TRIP steel 03X13AG19, and processing the obtained images using digital complexes. Design/methodology/approach: A laser treatment of TRIP steel (03X13AG19) with pulses of femtosecond duration was carried out in a melting mode. The source of the radiation is a femtosecond titanium-sapphire Ti:Al2O3 complex consisting of a predefining femtosecond generator “Mira Optima 900-F” and regenerative amplifier Legend F-1K-HE. Peculiarities of the surface structure of irradiated samples were studied using a Solver P47-PRO atomic force microscope. The structural-geometric parameters of the surface of the investigated steel treated with the femtosecond laser were determined using the software package Nova 1.0.26.1443 and the functions of the Image Analysis. Microstructural analysis was performed using a raster electron microscope JSM 6700F and a METAM-1P microscope. In this work, the digitization of images of microstructures obtained as a result of surface irradiation by highly concentrated energy streams of femtosecond duration has been carried out. The analysis of the surface structure of laser-structured materials was carried out using a metallographic complex with the software ImProcQCV. Findings: It has been revealed that the predetermined change of the laser treatment mode changes the microrelief and the shape and size of the fragments of the surface structure of the investigated steel. The use of digital image processing allowed to generalize the morphological features of the surface structure, to assess in detail the character of the microrelief, and to monitor under in-situ mode the structure and properties of the surface of the material being studied. Research limitations/implications: The obtained research results can be applied to stainless steels of various structural classes. Practical implications: Surface digitization significantly reduces the time for research, improves the quality and accuracy of the data obtained, makes it possible to conduct in-situ researches with the further implementation of the results using the Internet of Things technologies. Originality/value: A comprehensive approach is proposed for the estimation of parameters of laser-induced periodic surface structures (LIPSS) using a metallographic complex with the software ImProcQCV.
Źródło:
Journal of Achievements in Materials and Manufacturing Engineering; 2019, 93, 1-2; 5-19
1734-8412
Pojawia się w:
Journal of Achievements in Materials and Manufacturing Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The role of femtolaser in cataract surgery
Laser femtosekundowy w chirurgii zaćmy
Autorzy:
Nagy, Z.Z.
Szaflik, J.P.
Powiązania:
https://bibliotekanauki.pl/articles/9877.pdf
Data publikacji:
2014
Wydawca:
Okulistyka Weterynaryjna
Tematy:
femtolaser
femtosecond laser
cataract surgery
capsulorhexis
capsulotomy
eye
surgery
corneal wound
Źródło:
Okulistyka Weterynaryjna. e-kwartalnik dla lekarzy i studentów weterynarii; 2014, 2
2082-9256
Pojawia się w:
Okulistyka Weterynaryjna. e-kwartalnik dla lekarzy i studentów weterynarii
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 18

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