Teses / dissertações sobre o tema "Ultra-Fast optic"
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Fan, Xiaofei. "Contrôle ultrarapide de l'aimantation dans des hétérostructures à base de VO₂". Electronic Thesis or Diss., Université de Lorraine, 2022. http://www.theses.fr/2022LORR0271.
Texto completo da fonte(1) We have investigated the phase transition in ultrathin amorphous VO₂ and its physical mechanism: We have successfully prepared ultrathin (nano-scale) amorphous VO₂ films with significant phase transition by magnetron sputtering and demonstrated the phase transition of amorphous VO₂ - EGT. In addition, we quantitatively modeled the phase transition of amorphous VO₂ and classified different thicknesses of VO₂ into "strong system" (>5 nm) and "fragile system" (0-2 nm). For the strong system, the material properties are less affected by temperature, and the Arrhenius model is used to describe the electron transport of VO₂ phase transition. While for the fragile system, the material properties are more affected by temperature fluctuations, and the Vogel-Tammann-Fulcher model can be used for analysis. The results demonstrate the phase transition mechanism of amorphous materials and provide a new idea for understanding phase transition. In addition, this direct method of growing ultrathin VO₂ using magnetron sputtering is convenient and fast, and it can be grown in the same batch with other materials within the heterostructure, which is expected to promote the application of phase transition materials in practical devices.(2) We explored a method to dynamically regulate the interlayer exchange coupling by phase transition: we introduced the VO₂ into the ferromagnetic/nonmagneticspacer/ferromagnetic heterostructure, and successfully realized the reversible transformation of the antiferromagnetic coupling and ferromagnetic coupling through regulating conduction electrons by MIT of VO₂. At the same time, from the analysis of the change of magnetic properties, we clarify that the IEC induced by VO₂ in different electronic states is dominated by the RKKY and spin dependent tunneling. Furthermore, we fully investigate the physical root behind the regulation of IEC by the VO₂, and reveal the regulation mechanism of the interface spin effect by the regulation of electronic states of non-magnetic spacer. This part of the work proposes a novel approach to the dynamic regulation of IEC, which provides new ideas for the application of IEC in spintronic devices.(3) We study the dynamic regulation of spin-polarized hot electron transport by phase transition: In a ferrimagnetic/nonmagnetic diffusion channel/ferromagnetic heterostructure, we introduce VO₂ into the diffusion channel to control the electrical properties of the channel by MIT, and then dynamically regulate the transport of spin-polarized hot electrons generated by the ultrafast demagnetization of GdCo. By regulating the on/off of hot electrons in the channel, we achieve dynamic regulation of the magnetization of adjacent ferromagnetic layers. Meanwhile, with the optical property changes introduced by VO₂, we have successfully achieved the switching of the magnetization of ferromagnetic materials without AOS in ferrimagnetism excited by a single-pulse femtosecond laser. Furthermore, we have verified and analyzed the mechanism of this ultrafast modulation. In this work, we use the phase transition material VO₂ as a diffusion channel with controllable electrical properties to control the hot electron transport through MIT. The results show that the non-magnetic materials play an important role in various types of heterostructures
Koseoglu, Devrim. "Material Characterization With Terahertz Time-domain Spectroscopy". Phd thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/2/12611648/index.pdf.
Texto completo da fonte110>
crystals of various thicknesses to test the applicability of this algorithm. We have shown that the algorithm developed provides a quick way of eliminating the &ldquo
etalon&rdquo
reflections from the data. In addition, it is also shown that these &ldquo
etalon&rdquo
effects can be used for the frequency calibration of terahertz time-domain spectrometers.
Bahamin, Babak. "Fabrication and packaging of a 1X4 ultra fast all-photonic switch". Thesis, McGill University, 2005. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=83850.
Texto completo da fonteRamos-Ortiz, Gabriel. "Frequency conversion in conjugated organic molecules and its applications to ultra-fast pulse diagnostic and imaging". Diss., The University of Arizona, 2003. http://hdl.handle.net/10150/289952.
Texto completo da fonteEibna, Halim Md Zubaer. "Passively mode-locked picosecond Nd:KGW laser with low quantum defect diode pumping". Astro Ltd, 2016. http://hdl.handle.net/1993/31913.
Texto completo da fonteFebruary 2017
Dong, Peiliang. "On-chip ultra-fast data acquisition system for optical scanning acoustic microscopy using 0.35um CMOS technology". Thesis, University of Nottingham, 2009. http://eprints.nottingham.ac.uk/10667/.
Texto completo da fontePariente, Gustave. "Caractérisation spatio-temporelle d’impulsions laser de haute puissance". Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLS003/document.
Texto completo da fonteHigh power laser make it possible to reach very high intensities (up to 10²²W.cm⁻²). In order to get to this level of intensity, a moderate quantity of energy (on the order of the Joule) is concentrated in a very short time (on the order of tens of femtoseconds) onto a small surface (on the order of 1 μm²). These beams are therefore ultra-short and focused with a high aperture optic. These features mean that their diameter prior to focus is large and their spectral width is big. As a result, these beams are subject to spatio-spectral distorsions (of spatio-temporal couplings). After focus, these distorsions induce a dramatic reduction of the peak intensity. This situation is all the more true when the laser is more intense and its diameter and spectral width are therefore bigger. Despite their detrimental effects, spatio-temporal couplings can be of great interest when controlled. One can indeed introduce weak spatio-temporal couplings for experimental purposes. In the 1990s and 2000s, a big effort was put in order to characterize dans optimize the temporal profile of femtosecond lasers. Meanwhile, adaptative optics solutions were developed to control the spatial profil of ultra intense laser beams and provide the best focal spot achievable. By nature, this approach is blind to spatio-temporal couplings. Measuring these distorsions requires a spatio-temporal characterization. Before the start of this Phd thesis, spatio-temporal characterization methods already existed. Although none of these devices were ever adapted to the measurement of ultra-intense laser beams. During this Phd Thesis, we developped a new spatio-temporal characterization technique which we called TERMITES. This technique is based on a self-referenced Fourier transform spectroscopy scheme. TERMITES made it possible for us to perform the first total spatio-temporal characterization of a 100 TW laser (UHI-100 at CEA Saclay, France). The detection of spatio-temporal distorsions with the help of these measurements confirmed the need for a generalization of spatio-temporal characterization of ultra-high power lasers
Andreoli, Daria. "Contrôle spatio-temporel multi-spectral de la lumière en milieux complexes". Thesis, Paris 6, 2014. http://www.theses.fr/2014PA066679/document.
Texto completo da fonteThe transmission matrix allows to describe the effects generated by a multiple scattering medium on an incident monochromatic wave. The aim of the work presented in this dissertation is to develop the concept of transmission matrix of a multiple scattering medium to the more general case of a polychromatic ultra-fast pulsed light. In this dissertation we present and measure the multi-spectral transmission matrix of a complex medium. This new matrix describes the spatio-temporal coupling and the spatio-spectral coupling induced by the medium on a polycrhomatic illumination passing through it. The measurement of the multi-spectral transmission matrix allows us to control a monochromatic as well as a polychromatic source, after being scattered by the medium, in a deterministic way. We exploit this knowledge about the medium to compensate the distortions of the optical field by focusing, shaping and controlling spatially, spectrally and temporally an ultra-fast laser, thanks to the knowledge of the multi-spectral transmission matrix. This method paves the way towards many applications in the domain of imaging and light-matter interaction of light through complex media
McKee, Erik. "Femtosecond Filament Interaction as a Probe for Molecular Alignment". Master's thesis, University of Central Florida, 2013. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5991.
Texto completo da fonteM.S.
Masters
Optics and Photonics
Optics and Photonics
Optics
Lopes, Guido Nunes. "Medidas de tempos de relaxação ultra-curtos em DODCI com a técnica de eco de fótons com luz incoerente". Universidade de São Paulo, 1989. http://www.teses.usp.br/teses/disponiveis/54/54131/tde-14102014-100721/.
Texto completo da fonteThe photon echo with incoherent light technique (EFLI) has been used in this work for the measurement of the transverse relaxation time T2 in 3-3´-Dietiloxadicarboncyanine Iodide (DODCI) as a function of the temperature. A broad-band dye laser, pumped by the second harmonic of a Q-switched Nd+3 : YAG laser, was used in this experiment. The laser used Kiton Red 620 and rodamine 640 dyes, whose maxima output power are respectively around 598 and 610nm. The relaxation time T2 , which is inversely proportional to the homogeneous linewidth, depends on the temperature according to a T-1,9 Law. We found the value of T2 ranging from 0 to 30fs at 598nm and from 30 to 590fs at 610nm in the temperature range between 300 and 60K. The EFLI profiles can be described by means of a two-level quantum system model
Holmgren, Stefan. "Short Pulses in Engineered Nonlinear Media". Doctoral thesis, KTH, Fysik, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4234.
Texto completo da fonteQC 20100831
McCormick, Elizabeth Joan McCormick. "Optical Properties of Two Dimensional Semiconductors". The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1531907387651019.
Texto completo da fonteJuvé, Vincent. "Spectroscopie linéaire et ultra-rapide de nanoparticules métalliques : de l’ensemble au nano-objet individuel". Thesis, Lyon 1, 2011. http://www.theses.fr/2011LYO10163/document.
Texto completo da fonteThe size reduction of metals, from bulk to nanoparticles, induces significant modifications of their properties. For instance, the optical properties evolve and a new resonance, the localized surface plasmon resonance, appears in the optical spectrum and is responsible for the change of colors of metallic nanoparticles. This work is focused on studies of metals’ properties at the nanometric scale. In the first part, the vibrational and thermal properties are studied with a femtosecond spectroscopy technique. It is shown that it is possible to excite and detect optically vibrational frequencies in the terahertz domain by studying platinum nanoparticles formed by less than 100 atoms. The study of the thermal properties of the metallic nanoparticles (gold and silver) has shown that the boundary effect increases. This thermal boundary resistance, known as the Kapitza resistance, plays a dominant role in the heat transfer at the nanometric scale. A correlation between the experimental values of the thermal boundary resistance and the acoustic impedances of the boundary’s materials has been found. We have also shown that the Kapitza resistance is a decreasing function of the temperature in the 70-300K range. In the second part, the effect of the size reduction on the optical properties of non-spherical nanoparticles is observed. The Spatial Modulation Spectroscopy technique is used in order to locate and study individual gold nanorods. It is shown that the two geometrical parameters (the length and the diameter) of the nanorods influence the spectral linewidth of the localized surface plasmon resonance. This effect is not predicted by existing classical or quantum models
Torjesen, Alyssa Ashley. "An ultra-fast digital diffuse optical spectroscopic imaging system for neoadjuvant chemotherapy monitoring". Thesis, 2016. https://hdl.handle.net/2144/19470.
Texto completo da fonteJarvis, Thomas William. "Novel tools for ultrafast spectroscopy". Thesis, 2011. http://hdl.handle.net/2152/ETD-UT-2011-12-4456.
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Krampf, Andreas. "Non-instantaneous polarization in perovskite-like ferroelectrics revealed by correlated (ultra)fast luminescence and absorption spectroscopy. On the formation of self-trapped excitons in lithium niobate and their relation to small electron and hole polaron pairs". Doctoral thesis, 2020. https://repositorium.ub.uni-osnabrueck.de/handle/urn:nbn:de:gbv:700-202008283512.
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