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Artykuły w czasopismach na temat "Raman shift"
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Yang, XueXian, Yonghui Liu, Xin Juan Liu, Jin Zhang Peng, Heping Zhao i Chang Qing Sun. "Composition- and Temperature-Resolved Raman Shift of Silicon". Applied Spectroscopy 72, nr 4 (12.01.2018): 598–603. http://dx.doi.org/10.1177/0003702817744218.
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We formulated the composition and temperature dependence of the Si and Si1– xGe x Raman shift from the perspectives of bond order–length–strength correlation and local bond average approach. It is verified that the Raman shift Δω varies in the form of Δω ∝ zE1/2/ d, with inclusion of bond length d and energy E changing with temperature and composition. Numerical reproduction of the thermally induced Si1– xGe x phonon softening indicates that bond thermal expansion and energy loss dictate the frequency redshift, which resulted in quantitative information on the bond energy and the reference frequencies from which the Raman shifts proceed. Observations not only gain deeper insight into the mechanism of the Raman shift but also demonstrate the revealing power of Raman technique for the bonding thermodynamics.
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Gao, Yukun, i PG Yin. "Synthesis of cubic CdSe nanocrystals and their spectral properties". Nanomaterials and Nanotechnology 7 (1.01.2017): 184798041770174. http://dx.doi.org/10.1177/1847980417701747.
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The cadmium selenide nanocrystals are prepared by colloidal chemistry under mild conditions. X-ray diffraction and high-resolution transmission electron microscopy measurements indicate that as-prepared cadmium selenide nanocrystals are zinc blende cubic structure. We carry out an analysis of quantum size effect in the Raman spectra of cadmium selenide nanocrystals performed by utilizing the chemical bond theory of Raman peak shift developed recently. It is revealed that the shifts of Raman peaks in cadmium selenide nanocrystals result from the overlapping of the quantum effect shifts and surface effect shifts. The sizes of the as-prepared cadmium selenide nanocrystals obtained by employing the Raman peak shift theory are in good agreement with the nanocrystal sizes determined by high-resolution transmission electron microscopy.
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Fountain, Augustus W., Charles K. Mann i Thomas J. Vickers. "Routine Wavenumber Calibration of an FT-Raman Spectrometer". Applied Spectroscopy 49, nr 7 (lipiec 1995): 1048–53. http://dx.doi.org/10.1366/0003702953964886.
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A readily automated procedure for testing and calibrating the wavenumber shift scale of an FT-Raman spectrometer is described. The procedure uses atomic lines as wavenumber standards. An apodization procedure is used in accurately determining the line positions to a fraction of the sampling interval. A fiber-optic bundle conveniently couples the output from a hollow cathode lamp to the collection optics of the Raman accessory. Results are reported and compared for both thorium and neon atomic lines. Acetonitrile is suggested as a wavenumber shift standard, and peak shifts have been measured for its major features. Peak shift values are reported for 11 lines of cyclohexane.
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Zhou, Minghao, i Rongying Dai. "Study on Characteristic Raman Shift Screening Method Based on MPA for Raman Spectrum of Mine Water Inrush Source". Scientific Programming 2022 (23.08.2022): 1–8. http://dx.doi.org/10.1155/2022/5202265.
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In the process of mine water inrush disaster prevention, accurate and rapid identification of water inrush source type is of great significance to coal mine safety production. However, traditional hydrochemical methods have shortcomings such as time-consuming and complex detection. Therefore, a new idea of identifying mine water inrush source by Raman spectroscopy is proposed. Goaf water, roof sandstone fissure water, Ordovician limestone water, Taiyuan limestone water, and surface water as well as their mixed water samples are selected as research objects, and Raman spectral data of different water samples are collected by the Raman spectroscopy system. To eliminate the influence of laser power fluctuation and spectrometer system noise in Raman spectrum acquisition, detrend correction (DC), multiplicative scatter correction (MSC), standard normal variate transformation (SNV), first derivative (FD), and mean centering (MC) were used to preprocess the raw Raman spectra. Due to the large dimension and long analysis time of Raman spectrum data, the marine predator algorithm (MPA) is used to screen the characteristic Raman shifts of the Raman spectrum of water samples, and the characteristic Raman shift information that can best characterize the mine water samples is obtained. Finally, to verify the feasibility of MPA screening the characteristic Raman shifts of Raman spectrum of mine water inrush source, the selected characteristic Raman displacement information is used as input to construct BP neural network (BP), k-nearest neighbor algorithm (KNN), support vector machine (SVM), and decision tree (DT) classification models, respectively. Experiments show that SNV has the best preprocessing effect on the raw Raman spectrum, which can effectively eliminate part of the noise in the Raman spectrum data and improve the accuracy of Raman spectrum identification. Using MPA, 226 characteristic Raman shifts can be screened from 2048 Raman data points, reducing the number of Raman shifts to 11.04%, and the modeling accuracy of characteristic Raman shift information screened by MPA is higher than that of full Raman data. In addition, the average analysis speed of BP, KNN, SVM, and DT water source identification models is 7.61 times faster than that of all Raman data. The results show that MPA is adopted to screen the characteristic Raman displacement of mine water source Raman spectrum, which can effectively reduce the redundancy of Raman spectral data and greatly improve the speed of Raman spectral analysis, which is of great significance to ensure the real-time detection of the mine water source.
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Izadshenas, Saeid, Piotr Masłowski, Tobias Herr i Karolina Słowik. "Multiresonant metasurface for Raman spectroscopy beyond single molecule detection level". EPJ Applied Metamaterials 9 (2022): 11. http://dx.doi.org/10.1051/epjam/2022009.
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A metasurface in the metal-insulator-grating configuration is designed and optimised to support enhancement of coherent Raman signal of selected molecules orders of magnitude above the single-molecule detection threshold. The tunability is demonstrated by adjusting the structure to match selected Raman peaks of rhodamine, however, its spectral response is broad enough to cover a range of Raman shifts. Finally, the grating allows switching between distinct values of Raman shift with a single metasurface illuminated at different angles.
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Wang, Can, Bo Lin Cheng, S. Y. Wang, S. Y. Dai i Zhao Hui Chen. "Raman Spectra Study on Multilayered Compositional Graded (Ba0.8Sr0.2)(Ti1-xZrx)O3 Thin Films". Key Engineering Materials 280-283 (luty 2007): 1909–12. http://dx.doi.org/10.4028/www.scientific.net/kem.280-283.1909.
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Compositional graded thin films of (Ba0.8Sr0.2)(Ti1-xZrx)O3 (BSTZ) are grown on MgO by pulsed laser deposition technique with four BSTZ ceramic targets. Gradients of composition are achieved by artificially tailoring composition in multilayered thin films to form compositional graded layers (CGL). In each CGL four individual layers of BSTZ with x = 0.36, 0.18, 0.08 and 0 are grown^in series with equal thickness. Three kinds of CGL samples comprising one, two or four CGLs have been elaborated with the same total thickness by varying the thickness of each CGL. Raman spectra show existence of tetragonal structure in all the multilayered BSTZ thin films. Raman peak at 535 cm-1 shifts to high frequency with increasing of compositional gradient, and the peak at 750 cm-1 also shows a small shift to high frequency. Moreover, other Raman peak is observed at about 830 cm-1, which is associated with phonon mode of cubic phase, and such peak shifts towards lower frequency with increasing of compositional gradient. The shift of Raman peak is related to variation of internal stress in BSTZ thin film due to increasing compositional gradient.
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Amaechi, Ifeanyichukwu C., Andreas Ruediger i Alain Pignolet. "Phonon confinement and particle size effect on the low-frequency Raman mode of aurivillius phase Bi4Ti3O12 powders". RSC Advances 13, nr 8 (2023): 4917–23. http://dx.doi.org/10.1039/d2ra06297f.
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Both Raman shift, ω ∝ x−0.73, and linewidth, Γ ∝ x−0.38, exhibit a power law dependence on the particle size. The particle size-dependent lattice constant contributed to satisfactory explanation of the Raman shift.
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Piluso, Nicolò, Massimo Camarda, Ruggero Anzalone, Andrea Severino, Antonino La Magna, Giuseppe D'Arrigo i Francesco La Via. "Raman Stress Characterization of Hetero-Epitaxial 3C-SiC Free Standing Structures". Materials Science Forum 679-680 (marzec 2011): 141–44. http://dx.doi.org/10.4028/www.scientific.net/msf.679-680.141.
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Raman microscopy has been used to study the stress distribution on 3C-SiC/Si(100) micro-machined free standing structures. Linear scans along different structures reveal similar trends of the TO mode Raman Shift. We have found that, independently of the microstructure considered, the Raman frequency decreases close to the undercut. We compare our experimental measurements with FEM simulations finding that, close to the undercut, the stress tensor becomes non-diagonal, modifying the Raman shift to stress relation.
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Suda, Jun, i Petr Zverev. "Temperature Dependence of Raman Frequency Shift in SrWO4 Crystal Studied by Lattice Dynamical Calculations". Crystals 9, nr 4 (7.04.2019): 197. http://dx.doi.org/10.3390/cryst9040197.
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The frequency shift of the Raman modes in strontium tungstate (SrWO4) was investigated in the temperature range from 15 to 295 K. The experimental temperature dependence of the shift was analyzed using both the lattice dynamical calculations and the lattice perturbative approach. We found that the quartic anharmonic term of the first-order perturbation and the cubic term of the second-order perturbation, as well as the thermal expansion, contribute to the temperature shift of the highest-frequency Ag(ν1) mode. The values of the temperature sensitivity of the frequency shift of the Raman modes at room temperature were measured, which is important for developing high-power crystalline Raman lasers and frequency shifters.
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Shin, Y. J., W. J. Kim, H. Y. Kim i W. Bahng. "Dislocation Analysis of 4H-/6H-SiC Single Crystals Using Micro-Raman Spectroscopy". Materials Science Forum 740-742 (styczeń 2013): 481–84. http://dx.doi.org/10.4028/www.scientific.net/msf.740-742.481.
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Micro-Raman spectroscopy is an excellent non-destructive analysis method, which compensates for disadvantages of KOH method. Raman shift of A1(LO) and E1(TO) band at threading screw dislocation(TSD) were investigated in n-type on/off-axis 4H- and 6H-SiC single crystal wafers by Micro-Raman scattering at room temperature. The results showed that A1(LO) band were shifted toward higher frequency while the E1(TO) band were shifted toward lower frequency on the on-axis wafers. The shifts are caused by increasing electron concentration and lattice disorder near the dislocation core, respectively. In the off-axis wafers, no shifts were observed possibly due to the measurement geometry which does not contain whole dislocation core.
Rozprawy doktorskie na temat "Raman shift"
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Souther, Nathan Jon. "Light Shift Measurements of Cold Rubidium Atoms using Raman Pump-Probe Spectroscopy". Miami University / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=miami1250622906.
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Derbazi, Maqboula. "Étude des caractéristiques Raman et optique non-linéaire des bronzes de tungstène quadratiques (A6M2M’8O30)". Thesis, Reims, 2013. http://www.theses.fr/2013REIMS041.
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Des recherches très importantes ont été dédiées à l'étude des composés ferroélectriques de type bronze de tungstène quadratique (TTB). Cette thèse concerne la synthèse et la caractérisation de 7 matériaux TTB de formule générale A6M2M'8O30 (A = Sr2+, Ba2+ ou Pb2+, M = Ti4+, Zr4+ ou HF4+; M' = Nb5+ ou Ta5+). Ces composés cristallins de grande taille ∼100 nm ont été synthétisés sous forme de poudre. Les moyennes expérimentales : diffractions des rayons X, spectroscopie Raman, la microscopie électronique MEB et MET, l'optique non linéaire ONL, ont permis d'établir des relations étroites entre structure et propriétés physiques. Les susceptibilités optiques non linéaires de 2eme et 3eme ordres, χ(2), χ(3) de chaque composés ont été déterminées et les valeurs résultantes du χ(3) ne montrent pas les mêmes caractéristiques que χ(2), car le signal de THG est moins dépendant de structure que SHG qui requiert un milieu non-centrosymétrique. Le décalage fréquentiel (Δσ) des modes de vibrations entre les structures à base de strontium(Sr) et celles à base de Barium(Ba) a été constaté afin d'identifier les signatures propres de ces composés. L'interprétation de ces poudres n'était pas facile car les pics sont très délicats. Nos mesures expérimentales montrent clairement que les positions des pics peuvent être modifiées par le changement cationique au sein des matériaux, plus la maille cristalline est rigide, plus on a des pics plus discernables. La différence est nettement visible là ou l'émission est autour de 808 cm-1 pour la structure (Sr), alors que pour le (Br) elle est autour de 780cm-1. Nous attribuons ce Δσ (28cm-1) à la transition de groupe de symétrie spatiale de Pba2 vers P4bm. L'ensemble des résultats décrits dans ce travail ont montrés la grande variété des paramètres sur lesquels il est possible d'agir afin d'optimiser les compositions en vue d'une application spécifiqueRecently, very significant research has been devoted to the study of ferroelectric compounds of tetragonal tungsten bronze (TTB). This thesis deals with the synthesis and characterization of 7 TTB's material with general formula A6M2M'8O30 (A = Sr2+, Ba2+ or Pb2+, M = Ti4+, Zr4+ or HF4+, M '= Nb5+ or Ta5+). These crystalline compounds of large size ~ 100 nm were synthesized in powder form. The experimental Technics: X-ray diffraction, Raman spectroscopy, scanning electron microscopy SEM and TEM and nonlinear optics NLO, allowed us to establish close relationships between structure and physical properties. The nonlinear 2nd and 3rd order optical susceptibility χ(2), χ(3) of all compounds were determined and the resulting values of χ(3) did not show the same characteristics as measures of χ(2) because the THG signal is less dependent on the structure where SHG signal requires a non-centro-symmetric medium. The frequency shift between the vibration modes of structures containing strontium (Sr) and those based on Barium (Ba) has been detailed to identify signatures of these specific compounds. The interpretation of these powders wasn't that easy as these peaks are very delicate but our experimental results clearly show that the positions of the peaks can be modified by the change in cation materials, as long as the crystal lattice is more rigid, more we get discernible Raman modes. This difference is clearly visible where the emission is around 808 cm-1 for the structure Sr, whereas the Br it is centered around 780cm-1. We attribute these Δσ (28cm-1) to the transition of spatial symmetry group from Pba2 to P4bm. Results showed the wide variety of settings in which it is possible to act in order to optimize the compositions for a specific application
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Sjöqvist, Jonas. "Light interactions in flexible conjugated dyes". Doctoral thesis, Linköpings universitet, Beräkningsfysik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-109011.
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In this thesis methodological developments have been made for the description of flexible conjugated dyes in room temperature spectrum calculations. The methods in question target increased accuracy and efficiency by combining classical molecular dynamics (MD) simulations with time-dependent response theory spectrum calculations. For absorption and fluorescence spectroscopies a form of conformational averaging is used, where the final spectrum is obtained as an average of spectra calculated for geometries extracted from ground and excited state MD simulations. For infrared and Raman spectroscopies averaged spectra are calculated based on individual spectra, obtained for zero-temperature optimized molecular structures, weighted by conformational statistics from MD trajectories. Statistics for structural properties are also used in both cases to gain additional information about the systems, allowing more efficient utilization of computational resources. As it is essential that the molecular mechanics description of the system is highly accurate for methods of this nature to be effective, high quality force field parameters have been derived, describing the molecules of interest in either the MM3 or CHARMM force fields. These methods have been employed in the study of three systems. The first is a platinum(II) actylide chromophore used in optical power limiting materials, for which a ultraviolet/visible absorption spectrum has been calculated. The second is a family of molecular probes called luminescent conjugated oligothiophenes, used to detect and characterize amyloid proteins, for which both absorption and fluorescence spectra have been calculated. Finally, infrared and Raman spectra have been calculated for a group of branched oligothiophenes used in organic solar cells. In addition, solvation effects have been studied for conjugated poly\-eletrolytes in water, resulting in the development of two solvation models suitable for this class of molecules. The first uses a quantum meachanics/molecular mechanics (QM/MM) description, in which the solute mole\-cule is described using accurate quantum mechanical methods while the surrounding water molecules are described using point charges and polarizable point dipoles. The second discards the water entirely and removes the ionic groups of the solute. The QM/MM model provides highly accurate results while the cut-down model gives results of slightly lower quality but at a much reduced computational cost. Finally, a study of protein-dye interactions has been performed, with the goal of explaining changes in the luminescence properties of the LCO chromophores when in the presence of amyloid proteins. Results were less than conclusive.
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Pickartz, Sabrina. "All-optical control of fiber solitons". Doctoral thesis, Humboldt-Universität zu Berlin, 2018. http://dx.doi.org/10.18452/19468.
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Das Thema dieser Arbeit ist eine mögliche Steuerung eines optischen Solitons in nichtlinearen optischen Fasern. Es gelang, die interessierenden Solitonparameter wie Intensität, Dauer und Zeitverschiebung durch die Wechselwirkung mit einer dispersiven Welle geringer Intensität kontrollierbar zu modifizieren.
Es wird eine neue analytische Theorie vorgestellt für die Wechselwirkung zwischen Solitonen und dispersiven Wellen, die auf der Kreuzphasenmodulation in nichtlinearen Fasern beruht. Das vorgestellte Modell kombiniert quantenmechnische Streutheorie und eine Erweiterung der Störungstheorie für Solitonen aus der nichtlinearen Optik. Damit wurden folgende neue Ergebnisse erzielt: (1) Die Entwicklung aller Solitonparameter wird korrekt vorhergesagt. Insbesondere wird die mögliche Verstärkung der Solitonamplitude erfolgreich bestimmt. (2) Passende Intervalle der Kontrollparameter, die eine effektive Solitonmanipulation garantieren, können quantitativ bestimmt werden. (3) Der Raman-Effekt wurde in die Modellbeschreibung eingebunden. Die klassische Abschätzung der Eigenfrequenzverschiebung des Solitons durch den Raman-Effekt wurde verbessert und erweitert durch eine neue Relation für den einhergehenden Amplitudenverlust. Weiterhin wurden solche Kontrollpulse bestimmt, die dieser Schwächung des Solitons entgegenwirken. Im Unterschied zu früheren Versuchen liefert die hier entwickelte Modellbeschreibung die passenden Parameterbereiche für eine stabile Auslöschung des Raman-Effektes. (4) Obwohl die Wechselwirkung selbst auf der Kreuzphasenmodulation basiert, spielt der ”self-steepening“- Effekt, der die Bildung von optischen Schocks beschreibt, eine entscheidende Rolle für eine effiziente Veränderung der Solitonparameter.This work discusses the problem how to control an optical soliton propagating along a non- linear fiber. The approach chosen here is to change soliton delay, duration and intensity in a simple, predictable manner by applying low-intensity velocity-matched dispersive light waves. A new analytic theory of cross-phase modulation interactions of solitons with dispersive control waves is presented which combines quantum mechanical scattering theory, a modified soliton perturbation theory and a multi-scale approach. This led to the following new results: (1) The evolution of all soliton parameters is correctly predicted. In particular the possible amplitude enhancement of solitons is successfully quantified, which could not be obtained by the standard formulation of the soliton perturbation theory. (2) General ranges for control parameters are quantitatively determined, which ensure an effective interaction. (3) The Raman effect is incorporated into the theory. The classical estimation of the Raman self-frequency shift is refined and expanded by a new relation for the amplitude loss arising with the Raman self-frequency shift. Furthermore, control pulses are identified which cancel soliton degradation due to Raman effect. In contrast to previously reported attempts with the interaction scheme under consideration, even parameter ranges are found which lead to a stable cancellation of the Raman effect. (4) New qualitative insights into the underlying process emerged. The prominent role of the self-steepening effect could be isolated. Though the pulse interaction is mediated by cross-phase modulation, the self-steepening effect causes an essential enhancement leading to much stronger changes in soliton parameters.
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Jusserand, Bernard. "Dynamique de réseau des super réseaux semi-conducteurs : étude par diffusion Raman du système GaAs/AlAs". Paris 6, 1987. http://www.theses.fr/1987PA066054.
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Etude des "modes acoustiques replies" propagatifs et des modes optiques confines, coexistant dans ces structures. Mesure des fréquences et des intensités des raies associées aux modes replies comme fonction de la période, de la supermaille et de la longueur d'onde incidente; description quantitative en termes des modulations des propriétés acoustiques et photoélastiques. Démonstration du caractère essentiellement confine des modes optiques dont les fréquences, quantifiées, sont décrites par un modèle de chaine linéaire alternée; effets de l'épaisseur des couches et des conditions d'interface; étude de ce dernier aspect sur une série d'échantillons de raideur d'interface variée.
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Le, Van-Hoan. "Analyses de microvolumes de gaz par spectroscopie Raman : expériences quantitatives et modélisation des mélanges CO₂-CH₄-N₂". Electronic Thesis or Diss., Université de Lorraine, 2020. http://www.theses.fr/2020LORR0178.
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Les inclusions fluides naturelles peuvent fournir des informations quantitatives précieuses pour reconstruire les conditions de circulation des paléofluides. CO₂, CH₄ et N₂ sont les espèces gazeuses majoritaires le plus souvent rencontrées dans divers environnements géologiques. Cependant les données d’étalonnage des mélanges constitués de ces espèces pour une quantification de leurs propriétés PVX ne sont pas encore complètement établies. L'utilisation des données de calibration disponible dans la littérature peut donc entraîner des erreurs significatives. L'objectif central de ce travail de thèse est d’apporter des données d’étalonnage du signal Raman des gaz CO₂, CH₄, N₂ et de leurs mélanges, sur une gamme de pression de 5 à 600 bars, afin de pouvoir déterminer simultanément les propriétés PVX à une température fixée. Pour cela, des mélanges de gaz ont été préparés à haute pression par le biais d'un mélangeur (GasMix AlyTech) couplé avec un système de pressurisation développé au laboratoire GeoRessources. Des analyses in situ Raman des mélanges de gaz ont été réalisées dans des conditions contrôlées en utilisant le système HPOC couplé avec un microcapillaire transparent placé sur une platine microthermométrique (Linkam CAP500). L’incertitude des mesures des propriétés PVX à 22 ou 32 °C à partir de nos équations d’étalonnage est de < 1 mol%, ~ ± 20 bars et ~ ± 0,02 g.cm-³ pour la composition, la pression et la densité, respectivement. Un autre objectif du projet est d'interpréter la tendance de variation de la position du pic du N₂ et/ou CH₄ pour une compréhension approfondie. Deux modèles théoriques, i.e., le potentiel de Lennard-Jones 6-12 et le modèle « Perturbed hard-sphere fluid » ont été utilisés pour évaluer quantitativement la contribution des forces d'interaction intermoléculaire attractives et répulsives aux décalages des bandes de CH₄ et N₂. Un modèle prédictif a été proposé pour prédire la tendance de la variation de la position du pic du CH₄ jusqu'à 3000 bars en fonction de la pression et de la composition. En fin, l'applicabilité de nos données d'étalonnage aux autres systèmes gazeux ou dans d’autres laboratoires est discutée et évaluée. Des nouvelles données d’étalonnage universelles applicables dans d’autres laboratoires sont fournies. Un programme de calcul « FRAnCIs » avec une interface utilisateur a été développé pour rendre l'utilisation de nos données d'étalonnage accessibles au plus grand nombreQuantitative knowledge of species trapped within fluid inclusions provides key information to better understand geological processes as well as to reconstruct the conditions of paleofluid circulation. CO₂, CH₄, and N₂ are among the most dominant gas species omnipresent in various geological environments, but their quantitative PVX calibration data are not fully established yet. Using the previously published data can therefore lead to non-quantified errors, especially when applied to geological fluids containing generally several substances at elevated pressure and density. The aim of this work is to provide accurate calibration data for the simultaneous determination of PVX properties of pure gases or any binary and ternary mixtures of CO₂, CH₄, and N₂ over 5 to 600 bars at a fixed temperature, directly from Raman spectra. For this, gas mixtures were prepared and compressed using a mixer (GasMix AlyTech) coupled with a homemade pressurization system. Raman in situ analyses of gas mixtures were performed at controlled conditions using an improved HPOC system (High-Pressure Optical Cell) with a transparent microcapillary containing the prepared gas mixtures, placed on a heating-cooling stage (Linkam CAP500). Overall, the uncertainty of the measurement of the PVX properties of fluid inclusions from our calibration equations at 22 or 32 °C is < ± 1 mol%, ~ ± 20 bars, and ~ ± 0.02 g.cm-³ for molar proportion, pressure and density, respectively. The ensuing aim of the project is to interpret the variation trends of the peak position of the CH₄ and N₂ ν1 band for an in-depth understanding. Two theoretical models, i.e., Lennard-Jones 6-12 potential energy approximation and Perturbed hard-sphere fluid model were involved to quantitatively assess the contribution of the attractive and repulsive intermolecular interaction forces to the pressure-induced frequency shifts. A predictive model was also provided to predict the variation trend of the CH₄ ν1 band over a pressure range up to 3000 bars as a function of pressure and composition. Furthermore, the applicability of our calibration data to other laboratories and apparatus and to gas mixtures that contain a small amount of other species (e.g., H2, H2S) was discussed and evaluated. New universal calibration data applicable for other laboratories were then provided. A computer program “FRAnCIs” was also developed to make the application of our calibration data as convenient as possible via a user-friendly interface
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Maliarik, Mikhail. "Compounds with Non-Buttressed Metal-Metal Bond between Platinum and Thallium. Model Systems for Photoinduced Two-Electron-Transfer". Doctoral thesis, Stockholm : Tekniska högsk, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3174.
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Ayoub, Anas. "Sources laser ultrarapides performantes dans le moyen IR et le Tz". Thesis, Normandie, 2020. http://www.theses.fr/2020NORMR044.
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La sonde atomique tomographique est un instrument d’analyse de la matière à trois dimensions avec une résolution atomique. Cet instrument s’appuie sur l’effet de champ électrique généré à l’extrémité d’un échantillon taillé sous la forme d’une aiguille nanométrique pour faire évaporer les atomes de surface qui sont collectés par un détecteur à deux dimensions. La mesure du temps de vol des ions dont l’évaporation est déclenchée par une impulsion électrique ou optique permettent de remonter à la composition chimique en plus de la localisation 3D des atomes. Dans les sondes atomiques actuelles, l’évaporation atomique est déclenchée par un laser ultrarapide émettant dans l’UV. Cependant, l’interaction de la lumière UV avec la matière induit un échauffement thermique qui limite la résolution en masse de l’instrument et empêche son exploitation pour l’analyse de matériaux fragiles comme les composants biocompatibles. Ces travaux de thèse visent à étudier des solutions pour favoriser l’évaporation rapide tout en inhibant les effets thermiques indésirables dans le cadre d’une sonde atomique laser. Notre approche consiste à exploiter des impulsions ultracourtes dans le domaine du moyen infrarouge ou du THz en raison de leur grande énergie pondéromotrice associée à une faible énergie de photon. Ce manuscrit rapporte sur le développementd’un banc de génération et caractérisation d’impulsions THz intenses. Le couplage de ces rayonnements avec une nano-pointe métallique polarisée négativement a permis de caractériser le champ proche induit à la surface de la nano-pointe qui est fortement modifié par l’effet d’antenne de cette dernière. La deuxième partie rapporte sur le développement d’une source laser ultrarapide de haute cadence accordable dans le moyen infrarouge autour de 3 mm en exploitant des fibres en verre fluoréThe atome probe tomography is an instrument for analyzing matter in three dimensions with atomic resolution. This instrument relies on the effect of an electric field generated at the end of a sample cut into the shape of a nanoscale needle to evaporate the surface atoms which are collected by a two-dimensional detector. The measurement of the time of flight of the ions whose evaporation is triggered by an electrical or optical pulse makes it possible to measure the chemical composition in addition to the 3D localization of the atoms. In current atome probes, atomic evaporation is triggered by a high-speed laser emitting in the UV. However, the interaction of UV light with matter induces thermal heating which limits the mass resolution of the instrument and prevents its use for the analysis of fragile materials such as biocompatible components. This thesis work aims to study solutions to promote rapid evaporation while inhibiting unwanted thermal effects of the laser in atome probe. Our approach consists in exploiting ultrashort pulses in the mid-infrared or THz domain due to their high ponderomotive energy associated with low photon energy. This manuscript reports on the development of a bench for the generation and characterization of intense THz pulses. Coupling these radiations with a negatively polarized metallic nanotip has made it possible to characterize the near field induced at the surface of the nanotip, which is strongly modified by the antenna effect. The second part reports on the development of an ultra-fast laser source tunable in the mid-infrared around 3 mm using fluoride glass fibers
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Rannou, Isabelle. "Etudes sous pression de la transition de phase interpolytypique du sulfure de gallium". Paris 6, 1986. http://www.theses.fr/1986PA066063.
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Etude entre 0 et dollar GPA, permettant de mettre en évidence une transition de basse pression à 1,6 GPA; mesures de l'absorption optique et de l'indice de réfraction, de la diffusion Raman et de la diffusion Brillouin; analyse des variations a la transition. Description satisfaisante des variations des modes de vibration au moyen d'un modèle de dynamique réticulaire a forces centrales.
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Sarkar, Suman. "Probing effect of disorder in the electrical and optical properties on van der Waals heterostructure". Thesis, 2019. https://etd.iisc.ac.in/handle/2005/5030.
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In this thesis, we studied the transport properties of single-layer graphene and single-layer to few-layer
MoS2. We also studied the optical properties of MoS2 based single-layer, twisted bilayer devices. The main
observations of this thesis are summarized below:
1. We have observed that in graphene devices, the impurity number density increases with increasing
temperature, irrespective of the quality of the sample. In high mobility devices, the mobility increases
with decreasing temperature in contrast to low mobility devices where mobility decreased as we decrease
the temperature. We found the temperature coefficient of resistance to depend strongly on the gate bias
voltages. These observations have been explained using long-range and short-range scattering in the
light of classical Boltzmann transport formalism.
2. We have probed the sulfur vacancy energy level (which lies about 400 meV below the conduction band
minima) through conductance
fluctuation spectroscopy in few-layer MoS2 devices encapsulated between
hBN and HfO2. The resistance
fluctuations in these devices were orders of magnitude lower than
un-encapsulated devices fabricated directly on SiO2 substrates. The encapsulation also made the device
extremely stable against environmental degradation.
3. We observed the defect-mediated peak in the PL emission of single-layer MoS2 samples in low
temperatures, both on hBN substrate and SiO2 substrate. This defect state is present in all our
samples, irrespective of the device quality indicating the intrinsic nature of the defect level.
4. We have observed the Raman mode stiffening as we decrease the temperature and below a certain temperature it saturates. On the other hand, the FWHM of the Raman modes decreases with temperature
and saturates below a certain temperature. This temperature-dependent Raman shift and lifetime of the
Raman modes in single-layer and natural bilayer MoS2 can be understood from three-phonon scattering
process. We identified the presence of strain on hBN substrated MoS2 samples and nd that these
samples have much lower impurity charge concentrations as compared to those on SiO2 substrates.
5. We have observed an enhancement in photoluminescence in our pre-annealed artificial MoS2 bilayer.
When we perform thermal annealing at 300deg C in a high vacuum, the PL got quenched and the
coupling between the layers improved. This evolution of inter-layer coupling resulted in the appearance
of an `indirect' peak in PL emission, Raman shift in the out of plane Raman mode and also a new
layer-breathing mode peak in low-frequency Raman measurement
Książki na temat "Raman shift"
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J, Vanderaar Mark, i United States. National Aeronautics and Space Administration., red. A planar approximation for the least reliable bit log-likelihood ratio of 8-PSK modulation. [Washington, D.C.]: National Aeronautics and Space Administration, 1994.
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J, Vanderaar Mark, i United States. National Aeronautics and Space Administration., red. A planar approximation for the least reliable bit log-likelihood ratio of 8-PSK modulation. [Washington, D.C.]: National Aeronautics and Space Administration, 1994.
Znajdź pełny tekst źródłaCzęści książek na temat "Raman shift"
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Kobayashi, T., i S. Halle. "Optical Stark Shift of the Raman-Gain Spectrum in a Polydiacetylene PDA-DFMP Single Crystal". W Springer Proceedings in Physics, 68–72. Berlin, Heidelberg: Springer Berlin Heidelberg, 1994. http://dx.doi.org/10.1007/978-3-642-85060-8_17.
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de Wolf, Ingrid. "Finding the Stress from the Raman Shifts: A Case Study". W Raman Scattering in Materials Science, 104–6. Berlin, Heidelberg: Springer Berlin Heidelberg, 2000. http://dx.doi.org/10.1007/978-3-662-04221-2_4.
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Young, R. J. "Residual Stresses: Measurement by Raman Shift". W Encyclopedia of Materials: Science and Technology, 8170–72. Elsevier, 2001. http://dx.doi.org/10.1016/b0-08-043152-6/01464-9.
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Munawar Chaudhri, M. "Residual Stresses: Measurement by Raman Shift". W Reference Module in Materials Science and Materials Engineering. Elsevier, 2016. http://dx.doi.org/10.1016/b978-0-12-803581-8.03041-1.
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Watanabe, H., N. Hayazawa, Y. Inouye i S. Kawata. "Specific Raman band shift caused by mechano-chemical effect in tip-enhanced near-field Raman spectroscopy". W Nanoplasmonics - From Fundamentals to Applications, Proceedings of the 2nd International Nanophotonics Symposium Handai, 81–100. Elsevier, 2006. http://dx.doi.org/10.1016/s1574-0641(06)80011-2.
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Singh, Vickramjeet, i Ramesh L. Gardas. "Characterization Techniques for Graphene-Based Materials". W Graphene-based Carbocatalysts: Synthesis, Properties and Applications, 118–53. BENTHAM SCIENCE PUBLISHERS, 2023. http://dx.doi.org/10.2174/9789815050899123010008.
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Graphene bearing 2D (dimensional) layer of carbon atoms bonded in sp2 hybridized state are only 1 atomic-scale thick. However, the graphene can be extended along the horizontal dimension. The alternate double bonds leading to perfect conjugation with sp2 hybridization are exhibited in the hexagonal structure (honeycomb) of graphene. Theoretically and experimentally, the thicknesses of graphene have been determined and are in the nano-meter range. The extraordinary mechanical and electrical properties exhibited by such a 2D material have inspired scientists for device fabrication methodologies that can shift the synthesis from lab scale to large scale. It is considered the strongest material on earth, almost 100 times stronger (i.e., strength) than the best steel. Since graphene is only 1 atomic-scale thick and transparent, the characterization of graphene is complex but essential. The thickness down to one atomic layer in graphene can be identified by the light interference causing color contrast. Thus, optical microscopy-based methods enable the identification of graphene or its derivatives; on the other hand, Raman spectroscopy, which is sensitive to molecular bonding and geometric structure, is commonly employed for the quality determination of graphene-based materials. In this chapter, various characterization techniques are discussed, enabling the characterization of graphene and graphene-based materials (GBMs).
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Balafrej, Lamia. "Potential World". W The Making of the Artist in Late Timurid Painting, 108–49. Edinburgh University Press, 2019. http://dx.doi.org/10.3366/edinburgh/9781474437431.003.0004.
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Chapter 2 examines the representation of epigraphic inscriptions in Persian painting, inscriptions that appeared in pictures as ornaments adorning buildings. It argues for a shift in these inscriptions’ content and function in the late Timurid period. Until the mid-fifteenth century, inscriptions were mainly used to link painting to patron. But in the Cairo Bustan, the poetic verses were chosen so as to convey a celebration of the painter. As such they constitute an example of wasf (ekphrasis), a description of the visual that was also a discourse of praise. Moreover, the verses were picked from the poetry of ‘Abd al-Rahman Jami, a late fifteenth-century poet. The inscriptions thus staged a model for the pictures’ reception, a model in which the painting would circulate among famous poets such as Jami, prompting responses about the medium and its makers. A possible institutional setting for such a scenario was the majlis, a form of social gathering that fuelled the art of jawab (response).
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Rahman, Hakikur. "Social Impact of Virtual Networking". W Human Computer Interaction, 2014–22. IGI Global, 2009. http://dx.doi.org/10.4018/978-1-87828-991-9.ch131.
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Information has been defined as a set of data, facts, and figures that have been processed in such a way that they become meaningful. They make intelligence. When information is applied to doing something and is globally pertinent, it is said to have become knowledge. Information flow can be treated as an alternate wealth for a developing society and knowledge networking through virtual communication processes can break the lags and leads of information barriers. It can create an appropriate tool for achieving and facilitating exchange of information and knowledge among development partners, academia, policymakers, and the civil society at local, national, and global level to design and implement plans for development (Rahman, 2000). Virtual communities are the collection of online links to a particular node, examples of which are Yahoo!, eBay, Amazon, or smaller chat rooms or instant message buddy lists. These networks of links are freely chosen, democratic, unrestricted, and may even be anonymous or pseudonymous (Roberts, Smith, & Pollock, 2002). The concept of the virtual enterprise has emerged in management literature as the result of the fusion of technological advances and a claimed major socioeconomic paradigm shift. The virtual enterprise can be seen as a temporary alliance of contracted individuals or companies linked together by ICTs, which assembles for the purpose of a specific business task. Advocates of the virtual enterprise believe that it will replace the conventional model of organization in the 21s t century (Introna, More, & Cushman, 1999). The virtual network is being increasingly promoted as a model for a new form of ICT-mediated communication endeavor. Initially, the concept of the virtual network and the supportive role of ICTs as conceived by its proponents need to be clarified. Based on the initial understanding, the establishment of community information centres as the existing instance of virtual enterprise needs to be done.
Streszczenia konferencji na temat "Raman shift"
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Jia, Weiyi, i W. M. Yen. "Raman scattering from sapphire fibers". W OSA Annual Meeting. Washington, D.C.: Optica Publishing Group, 1989. http://dx.doi.org/10.1364/oam.1989.tuu12.
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We introduce an index matching technique which exploits the waveguiding properties of sapphire fibers, reduces the stray light level, and allows for the enhancement of Raman scattering signal- noise ratio. Raman scattering of sapphire fibers was conducted at room temperature using the 476.5 argon laser line. Red shifts were observed under tensile stress for both A1 g and E g phonon modes. The stress-induced Raman shifts for the A1 g modes are in good agreement with the theoretical calculations. The deformation potential constants used in these calculations were obtained from the literature of bulk sapphire measurement under compressive uniaxial stress. However, the E g modes shift to lower energy much faster than the calculated values. The behavior of the E g modes under tensile stress is not fully understood and may be due to the restricted dimension effects. Since the surface effects are 2-D, they should only influence the E g modes. Tensile stress tends to stretch the surface and relax the surface compression. Thus, a larger red frequency shift of the phonon modes may be expected compared with the bulk samples.
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Wang, Weiran, Yan Zhao i Xueying Han. "Raman shift of rare earth cobalt oxides". W 5th International Symposium on Advanced Optical Manufacturing and Testing Technologies, redaktorzy Yudong Zhang, José Sasián, Libin Xiang i Sandy To. SPIE, 2010. http://dx.doi.org/10.1117/12.865213.
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Dianov, E. M., K. K. Konstantinov, A. N. Pilipetskii i A. N. Starodumov. "The Soliton Frequency Stabilization and Raman Self-Frequency Shift Suppression in Fibers Doped Er And Tm Ions". W Nonlinear Guided-Wave Phenomena. Washington, D.C.: Optica Publishing Group, 1991. http://dx.doi.org/10.1364/nlgwp.1991.tua2.
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The possibility of the Raman self-frequency shift [1-3] suppression is of great interest for both the high bit rate communication lines and the lasers with fiber cavities [4]. In the communication lines for picosecond pulses the frequency shifts are small. Frequency drift toward a maximum of the gain profile in an active fibers can compensate to some extent the effect of self-frequency shift. The possibility of frequency stabilization by the effect of frequency pulling under the gain profile was investigated by Blow et al [5]. The frequency pulling to some fixed frequency was predicted instead of the growing with the fiber length soliton frequency shift. The suppression of self-frequency shift due to Raman amplification in the field of external pump wave was experimentally investigated by Gouveia-Neto et al [6].
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MacPherson, D. C., i J. L. Carlsten. "Generation of solitons in transient stimulated Raman scattering by optical phase shifts". W International Laser Science Conference. Washington, D.C.: Optica Publishing Group, 1986. http://dx.doi.org/10.1364/ils.1986.thl9.
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At the present time several groups are studying the use of optical phase shifts to initiate soliton formation in transient stimulated Raman scattering.1 Our experiments use a generator-amplifier Raman laser which is pumped by a frequency-doubled Nd:YAG laser at 532 nm. The Raman medium is hydrogen at 1-100 atm. We are studying the use of an electrooptic crystal to place a π phase shift in the Stokes beam between the generator and the amplifier. This shift momentarily causes energy transfer from the Stokes to the pump beam. Surprisingly, numerical calculations indicate that in one configuration the speed of the electrooptical switch need not be faster than the coherence time of the medium to generate a soliton pulse considerably shorter than the coherence time. Thus it appears that this technique can be used to generate pulses considerably shorter than those produced using standard electro-optical switching techniques. Numerical calculations and experimental results are presented.
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Piccoli, R., P. A. Carpeggiani, Y. G. Jeong, A. Rovere, R. Morandotti, G. Coccia, G. Fan i in. "Extreme Raman Red-Shift in Nitrogen-Filled Capillary Fibers". W CLEO: Applications and Technology. Washington, D.C.: OSA, 2021. http://dx.doi.org/10.1364/cleo_at.2021.jth3a.68.
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Kormokar, Robi, Md Hosne Mobarok Shamim i Martin Rochette. "Analytical Expression of Raman Induced Soliton Self- Frequency Shift". W CLEO: Applications and Technology. Washington, D.C.: OSA, 2021. http://dx.doi.org/10.1364/cleo_at.2021.jtu3a.66.
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Hause, A., i F. Mitschke. "Stable soliton pairs in the presence of Raman shift". W Nonlinear Photonics. Washington, D.C.: OSA, 2010. http://dx.doi.org/10.1364/np.2010.nmc2.
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Suzuki, Yoko. "Dynamical stokes shift observed by two-dimensional Raman spectroscopy". W International symposium on two-dimensional correlation spectroscopy. AIP, 2000. http://dx.doi.org/10.1063/1.1302889.
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Mitschke, F. M., L. F. Mollenauer i J. P. Gordon. "The Soliton Self Frequency Shift". W International Conference on Ultrafast Phenomena. Washington, D.C.: Optica Publishing Group, 1986. http://dx.doi.org/10.1364/up.1986.thc8.
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The "soliton self frequency shift", a continuous down shift in optical frequency of the soliton, is a new and important nonlinear pulse propagation effect in optical fibers. It is caused by a Raman self pumping of the soliton, by which energy is transferred from the higher to the lower frequency parts of its spectrum. Shifts of 10% of the optical frequency have already been achieved, and more is possible. Thus the effect should allow the derivation, from a single laser, of synchronized pulses of two frequencies for pump-probe measurements of configurational relaxation and other ultrafast phenomena. The effect also has important implications for the use of ultrashort pulses in long distance fiber communications systems.
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Monet, Frédéric, i Raman Kashyap. "Random Raman Supercontinuum fiber laser". W Nonlinear Photonics. Washington, D.C.: Optica Publishing Group, 2022. http://dx.doi.org/10.1364/np.2022.npm2e.4.
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We demonstrate the generation of a supercontinuum from modulation instability and Raman self-frequency shift in a distributed feedback random Raman fiber laser. This laser has the potential for random number generation at Tbps speeds.