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1
Costantino, Mauro. « Low-frequency noise spectroscopy as an effective tool for electric transport analysis ». Doctoral thesis, Universita degli studi di Salerno, 2018. http://elea.unisa.it:8080/xmlui/handle/10556/4375.
Texte intégralRésumé :
2016 - 2017In this work, several experiments and analyses performed by means of noise spectroscopy, on a broad typology of materials and compounds, are presented. Structural, DC electrical transport and noise properties are exposed for each investigated sample, and theoretical models and possible explanations of the experimental results are given to unravel physical phenomena. In particular, two distinct types of iron-chalcogenide superconductors are investigated, in their pristine and aged state, suggesting the more likely mechanism which generates the resistance fluctuations and resorting to Weak Localization theory. In the case of the polymer/carbon nanotubes composites, the fluctuation-induced tunneling model is introduced to explain the measured temperature dependence of the electrical conductance and the I-V curve behaviors. Then, noise measurements prove the existence of a structural phase transition occurring around 160 K within the perovskite compound and highlight the correlation between electronic defect states distribution and device performance. The variety of investigated devices and materials validates the soundness of the noise spectroscopy as an effective tool for electric transport analysis. [edited by author]
XXX ciclo
2
Pedurand, Richard. « Instrumentation for Thermal Noise Spectroscopy ». Thesis, Lyon, 2019. http://www.theses.fr/2019LYSE1356.
Texte intégralRésumé :
La résolution des interféromètres gravitationnels est limitée par le mouvement Brownien - ou bruit thermique - de leurs miroirs dans la partie centrale de leur bande de détection, entre 10Hz et 1kHz. La répartition en fréquence de ce bruit thermique est dictée par les mécanismes de dissipation d'énergie mécanique à l'origine de cette vibration aléatoire, en accord avec le théorème fluctuation-dissipation. Cette dissipation provient principalement des revêtements optiques déposés sur les miroirs pour leur donner leur réflectivité. Dans le but de réduire le bruit thermique, une nouvelle génération de détecteurs d'ondes gravitationnelles employant des miroirs refroidis à température cryogénique a été proposée. Le développement de nouveaux matériaux optiques en couche mince à faible dissipation mécanique, opérant à la fois à température ambiante et température cryogénique, demande donc de nouveaux outils expérimentaux. L'objet principal de cette thèse est la construction d'un nouvel instrument, le CryoQPDI, qui consiste en l'association d'un interféromètre haute résolution et d'un cryostat basé sur un refroidisseur pulse tube. Il est capable de mesurer directement le mouvement Brownien d'un microlevier entre 300 K et 7 K. En combinant des mesures effectuées sur un microlevier avant et après le dépôt d'une couche mince, il est possible de caractériser la dissipation mécanique interne de cette couche mince. Cet instrument participera ainsi à l'optimisation des revêtements optiques des futurs interféromètres gravitationnels, dans le but de minimiser les nuisances dues au bruit thermiqueThe resolution limit of gravitational wave interferometers is set by their mirrors' Brownian motion – or thermal noise - in the central part of their detection band, from 10Hz to 1kHz. This thermal noise frequency distribution is given by the mechanical energy dissipation mechanisms it originates from, in agreement with the fluctuation-dissipation theorem. This dissipation mainly derives from the optical coatings deposited on the mirrors to give them their reflectivity. To reduce this thermal noise, a new generation of gravitational wave detectors employing mirrors cooled to cryogenic temperature has been suggested. The development of new optical thin-film materials with low mechanical dissipation, operating at both room and cryogenic temperatures, therefore requires new experimental tools. The main object of this thesis is the construction of a new instrument, the CryoQPDI, which is an association between a high-resolution interferometer and a cryostat based on a pulse tube cooler. It can directly measure the Brownian motion of a microcantilever between 300 K and 7 K. By combining measurements made on a microcantilever before and after the deposition of a thin film, it is possible to characterize the internal mechanical dissipation of this thin film. This instrument will eventually contribute to the optimisation of optical coatings of future gravitational wave detectors, aiming at minimizing the limitations due to thermal noise
3
Sung, Youngkyu. « Non-Gaussian noise spectroscopy with superconducting qubits ». Thesis, Massachusetts Institute of Technology, 2018. http://hdl.handle.net/1721.1/120365.
Texte intégralRésumé :
Thesis: S.M. in Computer Science and Engineering, Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2018.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 91-95).
Most quantum control and quantum error-correction protocols assume that the noise causing decoherence is described by Gaussian statistics. However, the Gaussianity assumption breaks down when the quantum system is strongly coupled to a sparse environment or has a non-linear response to external degrees of freedom. Here, we experimentally validate an open-loop quantum control protocol that reconstructs the higher-order spectrum of a non-Gaussian dephasing process using a superconducting qubit as a noise spectrometer. This experimental demonstration of non-Gaussian noise spectroscopy protocol represents a major step towards the goal of demonstrating a complete noise spectral characterization of quantum devices.
by Youngkyu Sung.
S.M. in Computer Science and Engineering
4
Nafaa, Beya. « Etude du bruit électrique basse fréquence dans des technologies CMOS avancées ». Thesis, Normandie, 2018. http://www.theses.fr/2018NORMC273/document.
Texte intégralRésumé :
Les travaux réalisés pendant cette thèse se focalisent sur l'étude de transistors double grille UTBOX complètement délpétés fabriqués pour le nœud technologique 16 nm. Les performances de ces composants en courant continu et en fonction de la température ont été évaluées. Les pièges localisés dans le film de silicium ont été identifiés à l’aide de la spectroscopie de bruit basse fréquence, donnant ainsi la possibilité d'évaluer les étapes de fabrications afin de les optimiser. Un pic inhabituel de transconductance a été observé dans les caractéristiques de transfert obtenues à faibles températures (77 K et 10 K). Ce phénomène est plus probablement lié à un effet tunnel à travers des dopants diffusés à partir des extensions de source et drain dans le canal. Le mécanisme de transport quantique relié à la dégénérescence de niveaux d'énergie dans la bande de conduction a été mis en évidence à température cryogéniques et à très faibles polarisations. Une nouvelle approche théorique valide en inversion modérée a été développée pour les modèles de fluctuations de mobilité et de fluctuations de mobilité corrélés aux fluctuations du nombre de porteurs. Les résultats indiquent que le changement du mécanisme de transport des porteurs est accompagné par un changement du mécanisme du bruit en 1/fThe work done during this thesis focuses on the study of fully depleted double gate UTBOX transistors manufactured for the 16 nm technology node. The performances of these components in DC and as a function of temperature were evaluated. The traps located in the silicon film have been identified using low frequency noise spectroscopy, giving the possibility of evaluating the manufacturing steps in order to optimize them. An unusual peak of transconductance was observed in the transfer characteristics obtained at low temperatures (77 K and 10 K). This phenomenon is most likely related to a tunneling effect through dopants scattered from the source and drain extensions in the channel. The quantum transport mechanism related to the degeneracy of energy levels in the conduction band has been demonstrated at cryogenic temperatures and at very low polarizations. A new theoretical approach valid in moderate inversion has been developed for models of mobility fluctuations and mobility fluctuations correlated with the number of carriers fluctuations. The results indicate that the change in carrier transport mechanism is accompanied by a change in the 1 / f noise mechanism
5
Vartabi, Kashanian Samir. « Spectroscopie de bruit avec de grands nuages d'atomes froids ». Thesis, Université Côte d'Azur (ComUE), 2016. http://www.theses.fr/2016AZUR4059/document.
Texte intégralRésumé :
Nuage d'atomes de rubidium refroidi par laser. Ces mesures fournissent des informations sur la sourceet sur le milieu de propagation. Je considère une configuration particulière en transmission, le laserse propageant au travers du nuage atomique. Cette géométrie est pertinente pour étudier différentespropriétés, comme le mouvement des atomes. Cependant, le bruit intrinsèque du laser a unecontribution importante sur les spectres de bruit. Ce bruit technique peut alors devenir gênant pourextraire le signal étudié et une bonne compréhension du phénomène est donc essentielle.Expérimentalement, les spectres de bruit en intensité montrent un comportement différent auxfréquences basses et hautes. Alors que l'on observe la conversion "standard" du bruit de fréquence enbruit d'intensité pour les fréquences basses, la résonance atomique correspondant à un discriminateurde fréquence, des différences apparaissent à hautes fréquences. Nous montrons qu'une approche dechamp moyen, en associant une susceptibilité électrique au nuage atomique, est suffisante pourexpliquer les observations. Partant de ce modèle, les spectres permettent d'extraire des informationsquantitatives sur le laser et sur le nuage atomique. Ceci est connu sous le nom de spectroscopie debruit.La perspective est d'utiliser ces mesures de bruit afin d'obtenir une signature claire du laser aléatoireà atomes froids en étudiant la cohérence temporelle de la lumière émise. Cette thèse expose unerevue du phénomène de laser aléatoire, en particulier sur le laser à atomes froids et ses propriétés decohérenceIn this thesis, I present some measurements of fluctuations of light after interaction with a cloud oflaser-cooled rubidium atoms. These measurements can provide useful information on the sourceitself as well as on the medium in which light propagates. I address a particular configuration inwhich intensity noise are measured on a laser beam transmitted through the atomic cloud. Thisgeometry is relevant to investigate different properties, such as the atomic motion. However, in ourexperiment the intrinsic noise of the incident laser has an important contribution to the detected noisespectrum. This technical noise may be hard to distinguish from the signal under study and a goodunderstanding of this process is thus essential.Experimentally, the intensity noise spectra show a different behavior for low and high Fourierfrequencies. Whereas one recovers the "standard" frequency to intensity conversion at lowfrequencies, due to the atomic resonance as a frequency discriminator, some differences appear athigh frequencies. We show that a mean-field approach, which corresponds to describing the atomiccloud by a dielectric susceptibility, is sufficient to explain the observations. Using this model, thenoise spectra allow to extract some quantitative information on the laser noise as well as on theatomic sample. This is known as noise spectroscopy.The perspective of this thesis aims at applying noise measurement to obtain complementarysignatures of the cold-atom random laser by studying the temporal coherence of the emitted light.The manuscript therefore outlines a review on random laser phenomena with a focus on cold-atomrandom lasers and its coherence properties
6
Dang, Dung Do. « Tuneable Diode Laser Absorption Spectroscopy with Optical Fiber : Noise Analysis and Noise Reduction ». Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for elektronikk og telekommunikasjon, 2006. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-13089.
Texte intégralRésumé :
A prototype of a fiber based absorptionspectroscopy instrument is built. A single mode fiber pigtailDistributed Feedback laser (DFB) is used to scan a known$mbox{NH}_3$ absorption line near $1512nm$ ($6614cm^{-1}$). $2mm$diameter InGaAs PIN photodiodes are used to convert the light signalto electrical signals by use of special designed transimpedanceamplifiers. Laser modulation, coherent detection at twice themodulation frequency (second harmonic detection), other electronics,and digital signal processing are provided by Norsk Elektrooptikk.bigskip The DFB laser from NEL (NLK1S5EAAA) delivers 10mW fiberoutput and has maximum output around 30mW at maximum injectioncurrent of 200mA. This laser was found to be very quiet at dcoperation. However, in wavelength modulation spectroscopy operationit exhibit large modulation noise that was found to stem from thefiber coupling inside the laser module. A detection limit of$6times10^{-5}$ to $1times10^{-4}$ in absorbance unit with 0.712moptical path length and an effective measurement bandwidth of 52Hzwas achieved by this laser. This is significantly above thedetection limit with free air lasers which achieve $3times10^{-6}$relative absorbance (0.15ppm $mbox{NH}_3$ at room temperature andatmospheric pressure). The acquisition time for each concentrationmeasurement takes 3.2s. Hence, the response time is very fast whichis a common property of wavelength modulation spectroscopy.bigskip The modulation noise problem was attacked by an electronicnoise cancellation scheme. The idea was that since the noise sourceis inside the laser module and no external optical component can beused to reduce it. With great linearity and reliability propertiesof fused biconical taper (FBT) couplers the laser beam is split intotwo identical beams with nearly equal amount of the same noise. Onebeam, signal beam, is used to induce second harmonic signals in thegaseous path. The other beam goes directly to an identicalphotodetector and is used as a reference signal. Two specialdesigned noise canceller circuits were built to remove commonsignals. Both the circuits, based on current subtraction (notoptimized) or voltage subtraction, give comparable results. Themodulation noise was reduced by more than 12dB. A detection limit of$5times10^{-6}$ was achieved with this prototype. Even aftertransmitting the laser beam through a 3200 meter single mode fiber asignal to noise ratio (relative to 100ppm signal) of $180times$.Hence, a sensitivity is $1.1times10^{-5}$ in absorbance unit wasachieved with the basic noise canceller (not optimized). Thiscorresponds to a detection limit of 0.55ppm ammonia (12.5ppm withoutcancellation). The optimized noise canceller could reduce this by afactor of 3 or more.bigskipThe basic noise canceller based on current domain subtraction wasinvestigated in detail and optimized. This new circuit suppressedthe intensity modulation signal by more than 70dB. The 2f noise wasreduced to approximately 50ppb or $1.1times10^{-6}$ in absorbanceunit with an effective noise bandwidth of 52.3Hz and 1m optical pathlength. This is a record sensitivity with such simple electronics.The sensitivity of our fiber based prototype is limited by thefluctuating etalon fringing in the signal beam. Under normaloperation the prototype achieves approximately $pm20$ppb zero pointdrift in the concentration with an acquisition time of 48s (3.5Hznoise bandwidth). By our knowledge these results are the bestavailable and are competitive with the much more complex frequencymodulation spectroscopy technique.bigskipThese balanced transimpedance amplifiers also have the ability tomeasure the absorption spectra directly without modulation.Determining the absorption linewidth and its shape is now a straightforward task. By use of dual beam configuration and noisecancellation thermal effects that caused background fluctuationswere greatly suppressed. The laser delivers high intensity light,$sim22mW$. The dominating noise is the photocurrent shot noise andthe etalon fringing from optical components in the signal path.Remote sensing, in-situ, noninvasive measurements can be performedwith this instrument. In some cases it's flexibility, and remotesensing possibility are of great attractiveness for the industry.The sensitivity is also improved by a factor of two with the fiberbased tuneable diode laser absorption spectroscopy instrument.bigskipIn the end of this thesis we demonstrate the ability to measuremultiple absorption lines simultaneously. The number of measurementpaths is limited by the laser output power.
7
Chen, Zilong 1981. « Towards qubit noise spectroscopy by quantum bang-bang control ». Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/32721.
Texte intégralRésumé :
Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, June 2004.Includes bibliographical references (p. 89-91).
Quantum bang-bang control is a method of suppressing decoherence in qubits [VKL99, VL98]. To date, mathematically rigorous treatments of quantum bang-bang control offered little intuition. To complement existing approaches and to seek better understanding, I present intuitive pictures to think about quantum bang-bang control. In addition, I develop a formalism for treating phase noise moments of a qubit under quantum bang-bang control. Although the desired purpose of quantum bang-bang control is to remove noise, it is conceivable that it can be used to infer information about the noise process and coupling on a qubit. By using a simple random rotation model of single qubit dephasing, I demonstrate how quantum bang-bang control can distinguish between dephasing under different stochastic processes. I also show how quantum bang-bang control can determine noise coupling in a toy model where noise couples to the qubit via a fixed noise axis. These two demonstrations indicate the potential of quantum bang-bang control as a tool for qubit noise spectroscopy.
by Zilong Chen.
S.B.
8
Žáčik, Michal. « Šumová spektroskopie pro biologii ». Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2013. http://www.nusl.cz/ntk/nusl-219949.
Texte intégralRésumé :
This thesis contains glossary topic of spectroscopic measurement methods in broad bands of frequency. There is designed experimental measurement method for simple samples and biological samples measurements for noise spectroscopy in frequency range of 0,1 – 6 GHz, using broadband noise generator. There is realized the workplace and the measurement method is verified by measuring on selected samples. Measurements a displayed and analyzed.
9
程曦敏 et Hei-man Anita Ching. « Detector noise reduction in positron doppler broadening related spectroscopy systems ». Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2002. http://hub.hku.hk/bib/B31225846.
Texte intégral
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Ching, Hei-man Anita. « Detector noise reduction in positron doppler broadening related spectroscopy systems / ». Hong Kong : University of Hong Kong, 2002. http://sunzi.lib.hku.hk/hkuto/record.jsp?B25212114.
Texte intégral
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Dassonneville, Bastien. « Dynamics of Andeev states in a normal metal-superconductor ring : supercurrent fluctuations and spectroscopy of the minigap ». Phd thesis, Université Paris Sud - Paris XI, 2014. http://tel.archives-ouvertes.fr/tel-01011558.
Texte intégralRésumé :
A SNS junction made of two superconducting (S) electrodes separated by a normal (N) metal carries a non-dissipative current whose amplitude depends on the phase difference between the superconductors. The equilibrium properties of this system have been recently explored and are now well understood. The dynamics is still an open question: how does the current-phase relation evolves with a high-frequency phase modulation? What are the mechanisms and characteristic times that govern this evolution?To probe the dynamics of Andreev states, we measured the response of a phase($ \varphi $)-biased NS ring. The current response at frequencies $ f $ ranging from 200 MHz up to 14 GHz yields the magnetic susceptibility $ \chi(\varphi,f) $ whose real part $ \chi' $ gives the the non-dissipative response while the imaginary part $ \chi'' $ reveals the dissipation. Susceptibility is accessed by the modification of a superconducting resonator coupled to the NS ring.As expected, $ \chi' $ is simply the phase derivative of the supercurrent at low frequency, thus revealing the current-phase relation. More strikingly, we observed the emergence of two contributions at high-frequency. The first one is related to the relaxation of populations driven out-of-equilibrium by the excitation. It is associated with supercurrent noise. The second one corresponds to induced transitions. According to our analysis of the experiment, its phase dependence is accounting for by taking into account selection rules. It should also allows to perform the minigap spectroscopy. These results show that such finite frequency measurements reveal properties of SNS junctions that can not be accessed by standard transport experiments.
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Lefeuvre, Odile. « Characterization of stiffening layers by acoustic microscopy and Brillouin spectroscopy ». Thesis, University of Oxford, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.268173.
Texte intégral
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Hughes, Colan Evan. « New techniques in NMR spectroscopy ». Thesis, University of Oxford, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.297524.
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Garrity, Patrick Louis. « Nanoscale Thermal Fluctuation Spectroscopy ». ScholarWorks@UNO, 2009. http://scholarworks.uno.edu/td/912.
Texte intégralRésumé :
The utilization of thermal fluctuations or Johnson/Nyquist noise as a spectroscopic method to determine transport properties in conductors or semiconductors is developed in this paper. The autocorrelation function is obtained from power spectral density measurements thus enabling electronic transport property calculation through the Green-Kubo formalism. This experimental approach is distinct from traditional numerical methods such as molecular dynamics simulations, which have been used to extract the autocorrelation function and directly related physics only. This work reports multi-transport property measurements consisting of the electronic relaxation time, resistivity, mobility, diffusion coefficient, electronic contribution to thermal conductivity and Lorenz number from experimental data. Double validation of the experiment was accomplished through the use of a standard reference material and a standard measurement method, i.e. four-probe collinear resistivity technique. The advantages to this new experimental technique include the elimination of any required thermal or potential gradients, multi-transport property measurements within one experiment, very low error and the ability to apply controlled boundary conditions while gathering data. This research has experimentally assessed the gas pressure and flow effects of helium and argon on 30 nm Au and Cu thin films. The results show a reduction in Au and Cu electronic thermal conductivity and electrical resistivity when subjected to helium and argon pressure and flow. The perturbed electronic transport coefficients, attributed to increased electron scattering at the surface, were so dominant that further data was collected through straight-forward resistance measurements. The resistance data confirmed the thermal noise measurements thus lending considerable evidence to the presence of thin film surface scattering due to elastic and inelastic gas particle scattering effects with the electron ensemble.
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Wiegand, Julia Susan [Verfasser]. « Nonequilibrium spin noise spectroscopy on single quantum dots / Julia Susan Wiegand ». Hannover : Gottfried Wilhelm Leibniz Universität Hannover, 2019. http://d-nb.info/1182532616/34.
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Abbas, Chahine. « Optical spectroscopy of indirect excitons and electron spins in semiconductor nanostructures ». Thesis, Montpellier, 2019. http://www.theses.fr/2019MONTS049.
Texte intégralRésumé :
Ce travail porte sur l’étude optique de la dynamique de spin de deux systèmes: un gaz d’électrons dans des couches minces de CdTe d’une part et des excitons indirects dans un double puits quantique asymétrique en GaAs d’autre part. Des mesures de photoluminescence résolue en temps et en polarisation, et des mesures de spectroscopie pompe-sonde ont permis la détermination des temps de vie et des temps de relaxation de spin des excitons indirects. Le comportement général de la structure a été décrit, les contraintes techniques ont été mise en évidence et les meilleures conditions expérimentales ont été identifiées. En photoluminescence, nous avons mesuré des temps de vie de l’ordre de la quinzaine de ns et des temps de relaxation de spin de 5 ns dans le meilleur cas. L’utilisation d’un setup de spectroscopie pompe-sonde permettant d’étudier des délais très longs a démontré que des temps plus longs encore peuvent être atteints en séparant d’avantage deux impulsions lasers successives.Pour les électrons dans CdTe nous avons utilisé une autre méthode optique: la spectroscopie de bruit de spin qui s’est récemment imposée comme un outil de choix pour étudier la dynamique de spin dans les semi-conducteurs. Son principe consiste à sonder la dynamique d’un système de spins à travers ses fluctuations spontanées. Pour ce faire, ces fluctuations sont encodées dans le plan de polarisation d’un laser hors résonnant par l’intermédiaire de la rotation Faraday.Alors que les réalisations concrètes de cette technique se limitaient jusqu’à présent aux corrélations temporelles, nous proposons ici la première implémentation permettant d’accéder également aux corrélations spatiales du systèmes de spin. Cet accès à la dynamique spatiale est autorisé par une sélectivité en vecteur d’onde de la lumière diffusée venant de l’échantillon et nous offre l’opportunité de mesurer simultanément le temps de relaxation de spin et le coefficient de diffusion de spin. Ayant ainsi une vision complète de la dynamique de spin dans CdTe, nous avons pu confronter la physique du spin bien connue dans GaAs à nos observations dans CdTe. Contre toutes attentes, il semblerait que nos connaissances de GaAs ne soient pas directement transposables à CdTeThis work provides an optical study of spin dynamics in two different systems: electrons gas in n-doped CdTe thin layers, and indirect excitons in asymmetric GaAs coupled quantum wells. Time and polar resolved photoluminescence and pump-probe spectroscopy allowed the determination of both the lifetime and the relaxation time of indirect excitons.The global behaviour of the dedicated biased sample has been described, major technical constraints have been pointed out and optimal working conditions have been identified. In photoluminescence, we obtained a lifetime of 15 ns and a spin relaxation time of 5 ns. Pump-probe spectroscopy with an exceptional delay range shown that longer characteristic times could be obtained increasing the delay between two laser pulses.An other optical method has been used to study electrons in CdTe thin layers. Spin noise spectroscopy has recently emerged as an ideal tool to study dynamics of spin systems through their spontaneous fluctuations which are encoded in the polarisation state of a laser beam by means of Faraday rotation. Common spin noise setups provide only temporal fluctuations, spatial information being lost averaging the signal on the laser spot. Here, we demonstrate the first implementation of a spin noise setup providing both spatial and temporal spin correlations thanks to a wave vector selectivity of the scattered light. This gave us the opportunity to measure both the spin relaxation time and the spin diffusion coefficient. This complete vision of the spin dynamics in CdTe has been compared to our understanding of spin physics in GaAs. Against all odds, this knowledge seems not to be directly transposable from GaAs to CdTe
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Glasenapp, Philipp [Verfasser]. « Experimental advances in the optical spectroscopy of carrier spin noise / Philipp Glasenapp ». Aachen : Shaker, 2016. http://d-nb.info/112436515X/34.
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Collombon, Mathieu. « Résonance noire à trois photons sur un nuage d'ions calcium confinés ». Thesis, Aix-Marseille, 2019. http://www.theses.fr/2019AIXM0017.
Texte intégralRésumé :
Les travaux présentés dans cette thèse décrivent l’ensemble de la démarche expérimentale qui a été mise en place afin d’observer un piégeage cohérent de population à trois photons sur un nuage d’ions calcium confinés en piège radio-fréquence. La réalisation d’un tel processus cohérent repose sur des contraintes expérimentales fortes concernant la relation de phase entre les trois lasers impliqués dans le processus d’interrogation ainsi que sur leurs finesses spectrales. Notre approche est basée sur l’optimisation des performances d’un laser stabilisé à 411 THz (729 nm) pour atteindre une stabilité de fréquence relative inférieure à 10⁻¹⁴ à 1 s. Ces performances ont ensuite été transférées vers un peigne de fréquence optique. Le comportement de cet instrument ainsi que les performances du transfert sont présentés dans ces travaux. Le peigne est alors utilisé comme oscillateur de transfert pour asservir les deux autres lasers impliqués dans l’interrogation des ions (866 nm et 794 nm). Grâce à ce travail sur la mise en relation des trois sources laser, ainsi que l’optimisation de leur qualités spectrales nous avons pu observer les premières résonances noires à trois photons dans le spectre de fluorescence des ions 40 Ca⁺. Ces résultats originaux ainsi que les premières études systématiques du comportement de la résonance en fonction de différents paramètres expérimentaux sont présentés. L’analyse de ces résultats a permis de définir clairement les conditions expérimentales à respecter pour une potentielle utilisation métrologique de cette résonance qui émane d’une superposition cohérente d’état stable ou métastableThe work presented in this thesis describes the complete experimental set-up and approach to realize three-photon coherent population trapping in a cloud of radiofrequency confined calcium ions. The realization of such a population trapping relies on a stringent conditions of the phase relationship between the three lasers involved in the interrogation process, and also their spectral linewidths. Our experimental approach is based on the optimization of the performance of a frequency-stabilized titanium-sapphirelaser at 411 THz (729nm) at the 10⁻¹⁴ level, in term of relative frequency uncertainties. This laser’s fre-quency stability is subsequently transfered to a optical frequency comb by means of a phase-locked loop. Then the two other lasers involved (866 nm and 794 nm) are phase-locked to the optical frequency combwith the same technique. This work describes the transfer method along with its measured performances. With all the three lasers sharing the same ultra-stable frequency reference we have been able to experi-mentally observe for the first time a 3-photon dark resonance in the fluorescence spectra of the 40 Ca⁺, signature of a coherent population trapping in a 3-photon scheme. The dependence of this resonance at experimental parameters, such as laser powers, laser detunings and local magnetic field, have been studied and are presented in this work. The preliminary results have allowed to explain the behaviour of the dark resonance and explored conditions for the use of the 3-photon dark line as a THz frequency standard
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Brousseau, Jean-Luc. « Spectroscopie par effet tunnel inélastique de la brevetoxine et de l'octadécyltriméthoxysilane / ». Thèse, Trois-Rivières : Université du Québec à Trois-Rivières, 1999. http://www.uqtr.ca/biblio/notice/resume/03-2195693R.html.
Texte intégralRésumé :
Thèse (Ph.D.) - Université du Québec à Trois-Rivières, 1999.Le résumé et la table des matières sont disponibles en format électronique sur le site Web de la bibliothèque. CaQTU Comprend des références bibliogr.
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Turksen, Zeynep. « Applications In Broadband Thz Spectroscopy Towards Material Studies ». Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12612908/index.pdf.
Texte intégralRésumé :
The purpose of this work was to construct and analyze a THz time domain spectroscopy (THz-TDS) system by using a nanojoule energy per pulse ultrafast laser (non-amplified ultrafast laser or oscillator) source and a non-linear optical generation method for THz generation. First a THz-TDS system, which uses photoconductive antenna (PCA) method for THz generation, was built to understand the working principles of these types of systems. This THz-TDS system which used PCA for generation and a 2mm thick <110>
ZnTe crystal for detection had a bandwidth up to 1 THz with a 1000:1 signal to noise ratio (S/N). Using this system, various materials were investigated to study the usefulness of the obtained bandwidth. Absorption coefficient and refractive indices of the sample materials were calculated. Results showed that the bandwidth of the system was not sufficient to obtain fingerprint properties of these materials. In order to improve the system, optical rectification method was used for THz generation. A different THz-TDS system was built with a 1mm thick <
110>
ZnTe crystal used for the method of non-linear generation of THz radiation. Theoretical calculations of radiated intensity and electric field were done to analyze the expected bandwidth of the system. Results showed that the generation and the detection crystal thicknesses affect the obtained bandwidth of the system in that the bandwidth limiting factor is the crystal thickness and not the ultrafast laser pulse duration. Especially for detection, measurements obtained with both a 1mm thick and 2mm thick <
110>
ZnTe crystal showed that there was not much difference in bandwidth as was predicted by theory. Also in order to increase the signal to noise ratio, the optics used in the system were optimized. It was found that by using same focal lengths for focusing and collimating optics around the generation crystal and by using a short focal length parabolic mirror, S/N could be improved. After these improvements this THz-TDS system which uses optical rectification for THz generation and electro-optic method for THz detection had a larger bandwidth up to 3 THz but with a lower 100:1 signal to noise ratio.
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Larouche, Pascal. « Évolution temporelle d'une monocouche autoassemblée de dodécanethiol sur support métallique : étude par spectroscopie infrarouge / ». Trois-Rivières : Université du Québec à Trois-Rivières, 2003. http://www.uqtr.ca/biblio/notice/resume/18184507R.pdf.
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Byrne, Katherine. « The viscoelastic response of single biological molecules to thermal noise by atomic force spectroscopy ». Thesis, University of Leeds, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.432315.
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HOLM, DAVID ALLEN. « QUANTUM THEORY OF MULTIWAVE MIXING (RESONANCE FLUORESCENCE, SATURATION SPECTROSCOPY, MODULATION, PHASE CONJUGATION, QUANTUM NOISE) ». Diss., The University of Arizona, 1985. http://hdl.handle.net/10150/187980.
Texte intégralRésumé :
This dissertation formulates and applies a theory describing how one or two strong classical waves and one or two weak quantum mechanical waves interact in a two-level medium. The theory unifies many topics in quantum optics, such as resonance fluorescence, saturation spectroscopy, modulation spectroscopy, the build up of laser and optical bistability instabilities, and phase conjugation. The theory is based on a quantum population pulsation approach that resembles the semiclassical theories, but is substantially more detailed. Calculations are performed to include the effects of inhomogeneous broadening, spatial hole burning, and Gaussian transverse variations. The resonance fluorescence spectrum in a high finesse optical cavity is analyzed in detail, demonstrating how stimulated emission and multiwave processes alter the spectrum from the usual three peaks. The effects of quantum noise during the propagation of weak signal and conjugate fields in phase conjugation and modulation spectroscopy are studied. Our analysis demonstrates that quantum noise affects not only the intensities of the signal and conjugate, but also their relative phase, and in particular we determine a quantum limit to the semiclassical theory of FM modulation spectroscopy. Finally, we derive the corresponding theory for the two-photon, two-level medium. This yields the first calculation of the two-photon resonance fluorescence spectrum. Because of the greater number of possible interactions in the two-photon two-level model, the theoretical formalism is considerably more complex, and many effects arise that are absent in the one-photon problem. We discuss the role of the Stark shifts on the emission spectrum and show how the Rayleigh scattering is markedly different.
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Gom, Bradley Gustav, et University of Lethbridge Faculty of Arts and Science. « A cryogenic detector for submillimetre astronomy ». Thesis, Lethbridge, Alta. : University of Lethbridge, Faculty of Arts and Science, 1999, 1999. http://hdl.handle.net/10133/102.
Texte intégralRésumé :
Over the last several years, a submillimetre astronomical polarizing Fourier Transform Spectrometer (FTS) has been developed for use at the James Clerk Maxwell Telescope (JCMT) located atop Mauna Kea, Hawaii. A new liquid3 He cooled dual polarization detector system has been carefully designed for use with this FTS to eliminate noise problems encountered with UKT14, the JCMT facility bolometric detector. The objective of this thesis is to evaluate and optimize the performance of the new detector system. The design of the detector system is discussed, and the noise performance of the system is evaluated. The system performance is determined from photmetric, classical B-I, and spectroscopic measurements. Compared to UKT14, the intrinsic bolometer noise is reduced by a factor of - 2. More importantly, the spectral signal to noise ratio is improved by a factor of - 10 due to the elimination of electrical pickup and microphone noise in the detector signal.xiv, 156 leaves : ill. ; 28 cm.
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Gallant, Judith. « Spectroscopie et propriétés interfaciales du photosystème II en film monomoléculaire à l'interface air-eau / ». Thèse, Trois-Rivières, Université du Québec à Trois-Rivières, 1997. http://www.uqtr.ca/biblio/notice/resume/03-2183024R.htm.
Texte intégralRésumé :
Thèse (Ph.D.) - Université du Québec à Trois-Rivières, 1997.Le résumé et la table des matières sont disponibles en format électronique sur le site Web de la bibliothèque. CaQTU Bibliographie : f. 156-157.
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O'Hagan, Seamus. « Multi-mode absorption spectroscopy for multi-species and multi-parameter sensing ». Thesis, University of Oxford, 2017. https://ora.ox.ac.uk/objects/uuid:6f422683-7c50-47dd-8824-56b4b4ea941d.
Texte intégralRésumé :
The extension of Multi-mode Absorption Spectroscopy (MUMAS) to the infra-red spectral region for multi-species gas sensing is reported. A computationally efficient, theoretical model for analysis of MUMAS spectra is presented that avoids approximations used in previous work and treats arbitrary and time-dependent spectral intensity envelopes, thus facilitating the use of commercially available Interband Cascade Lasers (ICLs) and Quantum Cascade Lasers (QCLs). The first use of an ICL for MUMAS is reported using a multi-mode device operating at 3.7 μm to detect CH4 transitions over a range of 30 nm. Mode-linewidths are measured using the pressure-dependent widths of an isolated absorption feature in HCl. Multi- species sensing is demonstrated by measurement of partial pressures of CH4, C2H2 and H2CO in a low-pressure mixture with uncertainties of around 10%. Detection of CH4 in N2 at 1 bar is demonstrated using a shorter-cavity ICL to resolve spectral features in pressure-broadened and congested spectra. The first use of a QCL for MUMAS is reported using a commercially available device operating at 5.3 μm to detect multiple absorption transitions of NO at a partial pressure of 2.79 μbar in N2 buffer gas. The revised model is shown to enable good fits to MUMAS data by accounting for the time-variation of the spectral intensity profile during frequency scanning. Individual mode-linewidths are derived from fits to pressure- dependent MUMAS spectra and features from background interferences due to H2O in laboratory air are distinguished from those of the target species, NO. Data obtained at scan rates up to 10 kHz demonstrate the potential for achieving short measurement times. The development of a balanced ratiometric detection scheme for MUMAS with commercially available multi-mode lasers operating at 1.5 μm is reported for simultaneous detection of CO and CO2 showing improved SNR performance over previous direct transmission methods and suitability for a compact field-employable instrument. In addition, MUMAS spectra of CO2 are used to derive gas temperatures with an uncertainty of 3.2% in the range 300 - 700 K.
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Boudier, Dimitri. « Etude des phénomènes de transport de porteurs et du bruit basse fréquence en fonction de la température dans les transistors FinFET et GAA NWFET sub-10 nm ». Thesis, Normandie, 2018. http://www.theses.fr/2018NORMC220/document.
Texte intégralRésumé :
Les travaux menés pendant cette thèse se concentrent sur l'étude de technologies avancées de MOSFET, plus précisément de FinFET à triple-grille et de nanofils à grille enrobante. Ils ont été fabriqués pour le nœud technologique 10 nm, suivant le même procédé de fabrication à l'exception de la fabrication d'une quatrième grille pour les nanofils. Ces composants sont étudiés en régime statique afin de déterminer les principaux paramètres de leur modèle électrique. Des études à très faible température (< 10 K) et faible tension de drain (< 1 mV) montrent la présence de transport quantique dû aux niveaux d'énergie discrets dans les bandes de conduction et de valence. L'étude du bruit électrique en 1/f montre une bonne maîtrise du procédé d'oxydation de la grille ainsi que le changement de mécanisme de bruit sous l'effet de transport quantique. Différentes spectroscopies de bruit basse fréquence (i.e. étude du bruit de génération-recombinaison en fonction de la température) ont permis d'identifier les pièges contenus dans le film de silicium, donnant ainsi la possibilité d'incriminer les étapes de fabrications les plus critiquesThe work led within this thesis focuses on the study of advanced MOSFET technologies, more precisely of triple-gate FinFETs and Gate-All-Around nanowire FETs. They were fabricated for the 10-nm technological node, following the same recipe except for the build of a fourth gate in nanowire devices.The devices have been studied in static regime in order to determine the main parameters of their electrical model. Low temperature (<10 K) and low drain voltage (1mV) studies highlighted the existence of quantum transport that is due to discrete energy levels within the conduction and valence bands. The study of the 1/f noise testifies the good control of the gate oxidation process and evidences a change in the noise mecanism under quantum transport.Numerous low frequency noise spectroscopies (i.e. study of the generation-recombination noise as a function of the temperature) let us identify silicon film traps, thus giving indication of the critical process steps that are responsible for the generation-recombination noise
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Nnolim, Neme O. (Neme Okechukwu). « A comparison of signal-to-noise characteristics : Fourier transform enhanced magnetic rotation spectroscopy and dispersive spectrometry ». Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/38761.
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Sun, Yu. « SIGNAL PROCESSING FOR SHORT WAVE INFRARED (SWIR) RAMAN SPECTROSCOPY DIAGNOSIS OF CANCER ». Master's thesis, Temple University Libraries, 2017. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/446864.
Texte intégralRésumé :
BioengineeringM.S.
Raman spectroscopy is an effective optical analysis of the biochemically specific characterization of tissues without contrast agents or exogenous dyes. Applications of Raman spectroscopy include analysis and biomarker investigation, disease diagnosis and surgical guidance. One major challenge in Raman spectroscopy is removing inherent fluorescence background present in samples to acquire Raman signatures. In some tissues, like liver, kidney and darkly pigment skin, the auto-fluorescence background is strong enough to overwhelm the Raman peaks in conventional Near-Infrared (NIR) Raman systems. Recent publications have shown that using Raman systems with excitation sources with wavelengths beyond 830 nm and short-wave infrared (SWIR) InGaAs Array detectors resulted in dramatically reduced auto-fluorescence. The unique characteristics of Raman signals collected from SWIR systems versus NIR Raman systems requires inspection of the suitability of spectral pre-processing techniques. This thesis focused on the development of spectral processing techniques at three different steps; 1) detector background & noise reduction; 2) Auto-fluorescence background subtraction; 3) detection of outlier measurements to assist statistical classification. Detector background and noise reduction was compared between two different techniques, and a direct subtraction method resulted in better performance to reduce fixed pattern noise unique to InGaAs arrays. For the aim 2, three different algorithms for fluorescence background removal were developed, and a modified polynomial fitting method was found to be most appropriate for the low signal-to-noise (SNR) spectra. Finally, local outlier factor(LOF), a multivariate statistical outlier metric, was implemented in a two-stage fashion, and shown to be effective at identifying raw measurement errors and Raman spectra outliers. The overall outcome of this thesis was the evaluation of spectral processing techniques for SWIR Raman spectroscopy systems, and the development of specific techniques to optimize data quality and best prepare spectra for statistical analysis.
Temple University--Theses
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Gabbard, Ryan Dwight. « Identifying the Impact of Noise on Anomaly Detection through Functional Near-Infrared Spectroscopy (fNIRS) and Eye-tracking ». Wright State University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=wright1501711461736129.
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Lavoie, Hugo. « Propriétés structurales de protéines membranaires à l'interface air-eau : une étude par spectroscopie PM-IRRAS et rayons X / ». Thèse, Trois-Rivières : Université du Québec à Trois-Rivières, 2002. http://www.uqtr.ca/biblio/notice/resume/03-2238826R.html.
Texte intégralRésumé :
Thèse (Ph.D.) - Université du Québec à Trois-Rivières, 2002.Thèse présentée sous la forme de 3 articles scientifiques rédigés en anglais et acceptés par différentes revues scientifiques. CaQTU Comprend des bibliogr.
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Jones, Kolton K. « An Integration Setup if the in-situ Mass and Spectroscopic Analysis for Volatile Liquids or Solids ». TopSCHOLAR®, 2018. https://digitalcommons.wku.edu/theses/2064.
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To help address the growing need for more and better sensors, an attempt was made to produce an in-situ mass and spectroscopic analysis of liquid and solid samples, to characterize samples and sensors. Spectroscopic analysis consisted of Raman and FTIR where mass measurements were carried out. The sample or sensor’s holder would allow for spectroscopic analysis as well as expose the sample to high temperatures and various chemicals. While Raman and FTIR were successful in producing reliable and consistent data, the constructed watt balance was not. This failure was a result of eliminate vibrational noise.
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Knápek, Alexandr. « Metody přípravy a charakterizace experimentálních autoemisních katod ». Doctoral thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2013. http://www.nusl.cz/ntk/nusl-233613.
Texte intégralRésumé :
Téma doktorské práce se zabývá přípravou a popisem katod na bázi autoemise, jenž představují kvalitní a levný elektronový zdroj pro zařízení pracující s fokusovaným elektronovým svazkem. Pro přípravu kompozitní autoemisní katody byla využita elektrochemická metoda výroby. Kompozitní struktura katody zlepšuje proudovou stabilitu ve srovnání s čistě autoemisními katodami na bázi wolframu. Na základě charakterizace katody, jenž byla nově provedena metodou šumové spektroskopie, byla implementována technologická zlepšení stávající výroby. Metoda šumové spektroskopie je založena na analýze emisního proudu v časové a kmitočtové rovině, ale především poskytuje informace o nosiči náboje, o jeho pohyblivosti a dále o životnosti katody. Výsledky experimentální části byly rozšířeny teoretickými simulacemi, vedoucími k návrhu metodiky charakterizace vylepšené autoemisní katody.
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Sebastian, Ananthu. « Noise dynamics in multi-Stokes Brillouin laser ». Thesis, Rennes 1, 2020. http://www.theses.fr/2020REN1S068.
Texte intégralRésumé :
La diffusion Brillouin stimulée (SBS) est un processus d'interaction cohérent, pour lequel la lumière est diffusée à partir des ondes acoustiques générées optiquement. Les lasers Brillouin suscitent un très grand intérêt pour leur capacité à produire des largeurs de raie ultra cohérentes. Cette thèse est consacrée à la compréhension des propriétés de bruit des lasers à fibre Brillouin en anneau, fonctionnant avec de multiples ordres de Stokes. Tout d'abord, nous présentons une technique basée sur la méthode de ringdown de la cavité, qui permet de caractériser le coefficient de gain Brillouin directement à partir du sondage de la cavité laser. Ses avantages sont d'obtenir des paramètres à partir d'une seule expérience avec de faibles puissances optiques (quelques 10 milliwatts) pour des cavités courtes (quelques mètres de long, ou cavités intégrées). Deuxièmement, il est démontré qu'une largeur de raie intrinsèque de quelques dizaines de mHz peut être facilement obtenue en cascadant deux lasers Brillouin non résonants (pour lesquels la pompe effectue un seul passage à l'intérieur de la cavité). Afin d'obtenir ces résultats, la stabilité à long terme a été améliorée en utilisant une boucle d'asservissement de type Pound Drever Hall, ce qui nous permet de comparer nos résultats analytiques et expérimentaux. Malheureusement, nous n'avons pas exploré les limites fondamentales de la réduction du bruit en raison du plancher de bruit de notre banc de mesure. Troisièmement, un des travaux majeurs de cette thèse est l'étude analytique et expérimentale des propriétés du bruit, y compris le bruit de fréquence et le bruit relatif d'intensité, d'un laser Brillouin résonant (pour lequel, les ondes de pompe et de Stokes sont résonantes à l'intérieur de la cavité). En particulier, les impacts du facteur de qualité de la cavité fibrée en anneau, le désaccord de gain Brillouin ont été évalués très précisément sur les caractéristiques du RIN du laser telles que la réduction de l'amplitude du bruit et la fréquence de relaxation. Nous soulignons le fait que de nombreuses caractéristiques du bruit de fréquence sont liées aux propriétés du RIN par un couplage entre l'intensité et la phase. Nous montrons que le processus en cascade modifie la dynamique du laser Brillouin par rapport à celle d'un laser Brillouin monomode avec une seule composante de Stokes de premier ordre. Nos résultats expérimentaux sont en excellent accord avec nos simulations, obtenues grâce à notre système non linéaire décrivant le fonctionnement d'un laser Brillouin multi-Stokes. Cette bonne concordance est principalement due à notre capacité : à obtenir des valeurs très précises des paramètres de la cavité et du coefficient de gain Brillouin en utilisant la technique CRDM ; à atteindre une stabilité à long terme (plusieurs dizaines d'heures) ; à contrôler finement le désaccord entre la résonance de Stokes du laser et la fréquence du maximum de gain Brillouin. Nous démontrons expérimentalement pour la première fois que le bruit de fréquence est dégradé en présence d'une diffusion Brillouin anti-Stokes. Nous montrons également qu'un désaccord de gain de l'ordre de quelques centaines de kHz peut dégrader la réduction du bruit d'intensité ou également augmenter la largeur de raie par un couplage amplitude-phase. Toutes ces observations très fines nous permettent donc de fixer les limites fondamentales de tels systèmes laser comme : l'augmentation du bruit due aux ordres anti-Stokes ; le rôle du bruit de pompe et son interrelation possible avec la finesse de la cavité ; l'effet du désaccord inhérent aux ordres de Stokes plus élevés. Toutes ces conclusions sont les clés de la conception et de l'ingénierie de ces lasers à fibre Brillouin, qui suscitent actuellement beaucoup d'intérêt comme en témoignent les travaux en cours dans la communauté scientifique. Cette thèse de doctorat contribue à une meilleure compréhension des lasers Brillouin multi-StokesStimulated Brillouin Scattering (SBS) is a coherent interaction process in which light is scattered from optically generated acoustic waves. It is a powerful tool for microwave and optical signal processing, distributed sensing and spectroscopy. Brillouin lasers are attracting a lot of interest for their ability to produce ultra coherent linewidths. This thesis is devoted to the understanding of noise properties of Brillouin fiber ring lasers, operating with multiple Stokes orders. First, we present a technique based on the cavity ring-down method, which allows to characterize the Brillouin gain coefficient directly from probing the laser cavity. Its advantages are to obtain parameters from a single experiment with low optical powers (some 10 milliwatts) for short cavities (a few meters long, or integrated cavities). Secondly, it is shown that an intrinsic linewidth of a few tens of mHz can be easily obtained by cascading two non-resonant Brillouin lasers (for which the pump performs a single pass inside the cavity). In order to obtain these results, the long-term stability has been improved by using a Pound-Drever-Hall servo loop, which allows us to compare our analytical and experimental results. Unfortunately, we were unable to explore the fundamental limits of noise reduction due to the noise floor of our bench. Thirdly, one of the major works of this thesis is the theoretical and experimental study of the noise properties, including frequency noise and relative intensity noise, of a resonant Brillouin laser (for which pump and Stokes waves are resonant inside the cavity). In particular, the impacts of the fiber-ring-cavity quality factor, Brillouin gain detuning, are evaluated very precisely on the laser RIN features such as amplitude noise reduction and relaxation frequency. We emphasize the fact that many characteristics of the frequency noise are related to the RIN properties by a coupling between intensity and phase. We show that the cascade process modifies the dynamics of the Brillouin laser when compared to those of a single-mode Brillouin laser with a single first-order Stokes component. Our experimental results are in excellent agreement with our numerical simulations, obtained thanks to our non-linear system describing the operation of a multi-Stokes Brillouin laser. This good match is mainly due to our ability: to obtain very precise values of the cavity parameters and the Brillouin gain coefficient using the CRDM technique ; to achieve long-term stability (hours); to finely control the detuning between the laser Stokes resonance and the frequency of the Brillouin gain maximum. We demonstrate experimentally for the first time that frequency noise is degraded in the presence of anti-Stokes Brillouin scattering. We also show that a gain detuning of the order of a few hundred kHz can degrade the intensity noise reduction or also increase the linewidth by amplitude-phase coupling. All these very fine observations thus allow us to set the fundamental limits of such laser systems such as: the increase in noise due to anti-Stokes orders; the role of pump noise and its possible interrelation with cavity finesse; the effect of the detuning inherent to higher Stokes orders. All these conclusions are key to the design and engineering of these Brillouin fiber lasers, which are currently attracting a great deal of interest as evidenced by the work in progress in the scientific community. This PhD thesis contributes to a better understanding of multi-Stokes Brillouin lasers
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McGuire, John Andrew. « Femtosecond nonlinear spectroscopy at surfaces Second-harmonic probing of hole burning at the Si(111)7x7 surface and fourier-transform sum-frequency vibrational spectroscopy ». Berkeley, Calif. : Oak Ridge, Tenn. : Lawrence Berkeley National Laboratory ; distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy, 2004. http://www.osti.gov/servlets/purl/836810-xRj01W/native/.
Texte intégralRésumé :
Thesis (Ph.D.); Submitted to the University of California, Berkeley, CA (US); 24 Nov 2004.Published through the Information Bridge: DOE Scientific and Technical Information. "LBNL--56751" McGuire, John Andrew. USDOE Director. Office of Science. Office of Basic Energy Sciences. Materials Science and Engineering Division (US) 11/24/2004. Report is also available in paper and microfiche from NTIS.
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Ahmad, Mahmoud Mohamed Mahmoud [Verfasser]. « Highly Sensitive Sensor Based On Intracavity Laser Absorption Spectroscopy By Means of Relative Intensity Noise / Mahmoud Mohamed Mahmoud Ahmad ». Kassel : Universitätsbibliothek Kassel, 2011. http://d-nb.info/1009650874/34.
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Capra, S. « DEVELOPMENT AND CHARACTERIZATION OF AN INNOVATIVE LOW-NOISE HIGH-DYNAMIC-RANGE VLSI CHARGE-SENSITIVE PREAMPLIFIER FOR SOLID-STATE DETECTORS EMPLOYED IN NUCLEAR PHYSICS EXPERIMENTS WITH RADIOACTIVE ION BEAMS ». Doctoral thesis, Università degli Studi di Milano, 2016. http://hdl.handle.net/2434/359111.
Texte intégralRésumé :
The latest experimental results of the multichannel front-end ASIC of TRACE are shown. The device submitted to the foundry in the middle of 2014 and received at the end of the same year has been installed on a dedicated PCB and tested using a pulser. We then designed and realized a preamplifier board with eight ASICs for a total of 32 front channels and one back channel. We connected it to a highly-segmented planar silicon detector and acquired the spectrum of a 241Am-244Cm-239Pu triple alpha source obtaining an overall resolution around 3.5‰. The chip comprises four channels specifically designed for hole signals and one channel for electron signals. The power consumption is around 10 mW per channel as required by the specifications of TRACE. The main design goals are low noise and fast rise time. With proper shaping of the signals this device is capable of producing energy spectra with resolution of approximatively 1 keV. An innovative circuit architecture based on a Time-Over-Threshold technique boosts the dynamic range of the CSP by more than one order of magnitude. The rise time of the leading edge of the signals is fast enough to perform pulse-shape analysis of the waveforms. A peculiar feature of this device is the possibility to easily adjust a host of key parameters through an I2C bus. The bandwidth and sensitivity of the preamplifier can so be optimized according to the experimental needs on a case-by-case basis.
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Landi, Giovanni. « Organic semiconductor material and device characterization by low-frequency noise and admittance spectroscopy of polymer : fullerene solar cells and silicon/organic thin film heterodiodes ». Doctoral thesis, Universita degli studi di Salerno, 2015. http://hdl.handle.net/10556/1960.
Texte intégralRésumé :
2013-2014The main focus of the present work is addressed to the field of organic electronics, which has attracted increasing interest for the development of flexible, large area and low cost electronic applications, from light emitting diodes to thin film transistors and solar cells. The present work describes initially, the application of low-frequency electronic noise spectroscopy for the characterization of organic electronic devices as an innovative and non-destructive technique. In particular the role of the modification induced by thermal stress on the electronic transport parameters under dark conditions of a bulk-heterojunction polymer solar cell have been investigated in detail. The investigated organic solar cell is based on a blend between poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C6l-butyric acid methyl ester (PCBM), representing the classical reference structure regarding the polymer:fullerene type devices. Before the irreversible modification of the active layer, the solar cell has been modeled at low frequencies as a parallel connection between a fluctuating resistance RX(t) and a capacitance CX. Under dc biasing, the carriers injected into the active layer modify the equivalent electrical impedance thus changing the noise spectra. The experimental spectral trace can be interpreted by means of a theoretical model based on the capacitance Cμ, which takes into account the excess of minority carriers in the blend, and the device resistance Rrec. The measured electric noise is of 1/f-type up to a cut-off frequency fX, after which a 1/f3 dependence has been observed. The analysis of fX gives information regarding the recombination lifetime of the electrons in the active layer, while the voltage dependence of the Cμ provides information about the density of states for the lowest unoccupied molecular orbital (LUMO) level in the PCBM material. Furthermore, the voltage fluctuations spectroscopy has been used to detect modifications of the active layer due to thermal stress. The temperature has been identified as one of the external parameters that can accelerate the parameter degradation. The analysis of the flicker and the thermal noise at low frequency reveals a decrease of the charge carrier zero-field mobility after a thermal cycle. This effect has been related to morphological changes of the solar cell active layer and the interface between the metal contact and the blend. Moreover, the influence of the solvent additives during the film preparation stage on the electronic transport in the solar cells has been studied by means of noise spectroscopy, and a detailed comparison of the optoelectronic properties of solar cells prepared with different blends has been made. On one side, a P3HT/PCBM based bulk heterojunction solar cell is one of the most prominent candidates for a polymer solar cell, but on the other side, its conversion efficiency is limited by poor longwavelength absorption. One way to increase the conversion efficiency is to modify the active layer absorption by the addition of materials, that increase the absorption of light in the red and infrared spectral region. One of the most promising materials for this task are inorganic quantum dots (QDs). In the present study we choose InP/ZnS quantum dots with an emission peak wavelength of about 660 nm. ... [edited by Author]
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Ilhe, Paul. « Estimation statistique des éléments d'un processus shot-noise ». Electronic Thesis or Diss., Paris, ENST, 2016. http://www.theses.fr/2016ENST0052.
Texte intégralRésumé :
Dans le cadre de la spectrométrie gamma, cette thèse introduit de nouveaux estimateurs non paramétriques de l’intensité et de la densité des marques d’un processus shot-noise à partir d’un nombre fini d’observations du processus échantillonné à basse fréquence. Les méthodes proposées utilisent une relation non linéaire reliant la fonction caractéristique de la loi marginale du processus à la densité des marques. Elles sont particulièrement rapides et possèdent l’avantage d’être efficaces mêmes pour des intensités élevées. Les performances de ces méthodes sont étudiées quantitativement et illustrées à la fois pour des données simulées et réelles provenant du CEA Saclay. En particulier, les estimateurs de la densité des marques permettent de corriger les artefacts de pics multiplesIn the context of gamma-spectroscopy, this thesis introduces new nonparametric estimators of the intensity and the mark’s density of a shot-noise process based on a finite sample of low-frequency observations of this stochastic process. The methods developed exploit a nonlinear functional equation linking the characteristic function of the marginal law of the shot-noise with the mark’s density function. They are particularly time-efficient and perform well even for processes with high intensity. The performances of the methods are quantitatively studied and illustrations are provided both on simulated datasets and real datasets stemming from the CEA. In particular, our methods corrects the multiple peak artefacts that arises with classical techniques
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Zhang, Da. « On the Low Frequency Noise in Ion Sensing ». Doctoral thesis, Uppsala universitet, Fasta tillståndets elektronik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-320544.
Texte intégralRésumé :
Ion sensing represents a grand research challenge. It finds a vast variety of applications in, e.g., gas sensing for domestic gases and ion detection in electrolytes for chemical-biological-medical monitoring. Semiconductor genome sequencing exemplifies a revolutionary application of the latter. For such sensing applications, the signal mostly spans in the low frequency regime. Therefore, low-frequency noise (LFN) present in the same frequency domain places a limit on the minimum detectable variation of the sensing signal and constitutes a major research and development objective of ion sensing devices. This thesis focuses on understanding LFN in ion sensing based on both experimental and theoretical studies. The thesis starts with demonstrating a novel device concept, i.e., ion-gated bipolar amplifier (IGBA), aiming at boosting the signal for mitigating the interference by external noise. An IGBA device consists of a modified ion-sensitive field-effect transistors (ISFET) intimately integrated with a bipolar junction transistor as the internal current amplifier with an achieved internal amplification of 70. The efficacy of IGBA in suppressing the external interference is clearly demonstrated by comparing its noise performance to that of the ISFET counterpart. Among the various noise sources of an ISFET, the solid/liquid interfacial noise is poorly studied. A differential microelectrode cell is developed for characterizing this noise component by employing potentiometry and electrochemical impedance spectroscopy. With the cell, the measured noise of the TiN/electrolyte interface is found to be of thermal nature. The interfacial noise is further found to be comparable or larger than that of the state-of-the-art MOSFETs. Therefore, its influence cannot be overlooked for design of future ion sensors. To understand the solid/liquid interfacial noise, an electrochemical impedance model is developed based on the dynamic site-binding reactions of surface hydrogen ions with surface OH groups. The model incorporates both thermodynamic and kinetic properties of the binding reactions. By considering the distributed nature of the reaction energy barriers, the model can interpret the interfacial impedance with a constant-phase-element behavior. Since the model directly correlates the interfacial noise to the properties of the sensing surface, the dependencies of noise on the reaction rate constants and binding site density are systematically investigated.
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Sainton, Grégory. « Spectroscopie des supernovæ à grand décalage vers le rouge ». Phd thesis, Université Claude Bernard - Lyon I, 2004. http://tel.archives-ouvertes.fr/tel-00106153.
Texte intégralRésumé :
Cette thèse a permis de comparer les caractéristiques spectrales des supernovæ de type Ia en fonction dudécalage vers le rouge ("évolution"). Dans le cadre des collaborations Supernova Cosmology Project (SCP) et SuperNova Legacy Survey (SNLS), dont l'objectif scientique commun est l'étude de l'énergie noire à l'aide de supernovæ de type Ia à grand décalage vers le rouge, une part importante du travail de thèse est consacrée à la réduction des données spectrales,
étape nécessaire pour obtenir le spectre physiquement exploitable à partir de données observées. La réduction de l'ensemble des spectres SCP issus du spectrographe à échellettes Keck-ESI a permis d'obtenir des supernovæ de type Ia parmi les plus lointaines jamais observées. Dans l'expérience SNLS, l'identication spectroscopique est essentiellement réalisée avec le spectrographe longue fente FORS1 monté au foyer du VLT UT1. Pour le SNLS, il s'agit de réduire et d'identier une dizaine de spectres par lunaison pendant 5 ans. Dans le cadre de cette thèse, un logiciel d'identication en temps réel de SNIa a été developpé, il permet d'établir le type, le décalage vers le rouge et l'âge du candidat quasi automatiquement. Il évalue aussi la contamination
de la galaxie hôte (dont on peut aussi estimer la morphologie) dans le spectre. Le logiciel a été testé sur un échantillon de spectres analysés en détail.
Par ailleurs, pour certains d'entre eux, on a mesuré la vitesse du CaH&K (3945.12Å) dans la photosphère puis
on a comparé les résultats avec les mêmes mesures réalisées sur un lot de spectres proches. Ce résultat a permis de conrmer l'hypothèse de standardité des SNIa à grand décalage vers le rouge. C'est une hypothèse fondamentale pour mesurer les paramètres cosmologiques avec les supernovæ de type Ia.
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Naji, Majid. « Raman Signal Enhancement and CARS Microscopy ». Thesis, Université d'Ottawa / University of Ottawa, 2014. http://hdl.handle.net/10393/31538.
Texte intégralRésumé :
Raman biosensors are appealing for many biomedical applications, due to their accuracy and speed. In addition, Raman microscopy is a non-labeled imaging technique that offers chemical contrast based on Raman vibrational frequencies. However, the weak Raman signal represents a significant obstacle to using Raman in biological applications. The objective of my PhD research, presented in this thesis, is to enhance the Raman signal, thereby enabling it to be used in a wide variety of biomedical applications.
More specifically, the research focuses on two different Raman signal enhancement techniques. The first is to improve the Raman signal using hollow-core photonic crystal fibers; this enhanced the Raman signal of ethanol 40 times. The second approach is by generating a coherent anti-Stokes Raman scattering (CARS) signal.
We demonstrated CARS microscopy of myelin (lipid-rich) structures using a single femtosecond Ti:sapphire laser, and a photonic crystal fiber (PCF) with two closely lying zero dispersion wavelengths (ZDWs). Generating low noise supercontinuum (Stokes beam) out of two closely lying ZDW PCFs, enabled us to perform fast data acquisition (84 μs per pixel) CARS imaging using a homebuilt microscope. However, the application of this fiber is often limited to CARS imaging of molecular species with vibrations at wavenumbers ≥ 2000 cm−1 Raman shift. In addition, as it is not a polarization maintaining fiber, it cannot be used for polarization CARS microscopy. A polarization-maintaining PCF with two far-lying zero dispersion wavelengths offers important advantages for polarization CARS microscopy, and for CARS imaging in the fingerprint region. This PCF, though commercially available, has had limited use for CARS microscopy in the C-H bond region. The main problem is that the supercontinuum from this fiber is typically noisier than that from a standard PCF with two closely-lying zero dispersion wavelengths. To overcome this, we determined the optimum operating conditions for generating a low-noise supercontinuum out of a PCF with two far-lying zero dispersion wavelengths, in terms of the input parameters of the excitation pulse. We measured the relative intensity noise (RIN) of the Stokes and the corresponding CARS signal, as a function of the input laser parameters in this fiber. We demonstrated that the results of CARS imaging using this alternate fiber are comparable to those achieved using the standard fiber for input laser pulse conditions of low average power, narrow pulse width with a slightly positive chirp, and polarization direction parallel to the slow axis of the selected fiber.
Finally, we demonstrated a novel fiber-delivered, portable, multimodal CARS exoscope, for minimally invasive in-vivo imaging of tissues. The device was based on a micro-electromechanical system-scanning mirror and miniaturized optics, and light delivery by photonic crystal fibre. A single Ti:sapphire femtosecond laser approach is used to produce CARS and two photon excitation fluorescent and second harmonic generation images of different samples using the new setup. The high resolution and distortion-free images achieved with various samples, particularly in the reverse direction (epi), successfully demonstrate proof of concept, and paves the way to minimally or non-invasive in vivo imaging. Moreover, combining this novel endoscope with a portable femtosecond fiber laser will accelerate delivering multimodal nonlinear imaging endoscopy/microscopy to clinical bed-side applications.
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Beaudoin, Normand. « Méthode mathématique et numérique de haute précision pour le calcul des transformées de Fourier, intégrales, dérivées et polynômes splines de tout ordre ; Déconvolution par transformée de Fourier et spectroscopie photoacoustique à résolution temporelle / ». Thèse, Trois-Rivières : Université du Québec à Trois-Rivières, 1999. http://www.uqtr.ca/biblio/notice/resume/03-2201231R.html.
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Naude, Natali. « Proton magnetic resonance spectroscopy to evaluate in vivo breast tissue chemistry at 3.0 Tesla ». Thesis, Queensland University of Technology, 2021. https://eprints.qut.edu.au/225943/1/Natali_Naude_Thesis.pdf.
Texte intégralRésumé :
The research utilised in vivo 2D magnetic resonance spectroscopy in conjunction with standard breast MRI to investigate MR-visible characteristics associated with breast density and menopausal status. Statistically significant differences were recorded in various neutral lipids and metabolites, and with further development, may enable non-contrast MRI to evaluate breast cancer risk, avoiding the use of gadolinium-based contrast media. The tentative assignment of methylmalonic acid (MMA), which has been associated with cancer proliferation, was also made. Another spectral region was identified relating to polyunsaturated fatty acid content in breast tissue. PUFAs have been shown to have a protective effect against breast cancer.
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Zocca, F. « New technologies for low-noise wide-dynamic range preamplification of HPGe segmented detector signals ». Doctoral thesis, Università degli Studi di Milano, 2008. http://hdl.handle.net/2434/60937.
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Foltynowicz, Aleksandra. « Fiber-laser-based noise-immune cavity-enhanced optical heterodyne molecular spectrometry ». Doctoral thesis, Umeå universitet, Institutionen för fysik, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-22269.
Texte intégralRésumé :
Noise-immune cavity-enhanced optical heterodyne molecular spectro-metry (NICE-OHMS) is one of the most sensitive laser-based absorption techniques. The high sensitivity of NICE-OHMS is obtained by a unique combination of cavity enhancement (for increased interaction length with a sample) with frequency modulation spectrometry (for reduction of noise). Moreover, sub-Doppler detection is possible due to the presence of high intensity counter-propagating waves inside an external resonator, which provides an excellent spectral selectivity. The high sensitivity and selectivity make NICE-OHMS particularly suitable for trace gas detection. Despite this, the technique has so far not been often used for practical applications due to its technical complexity, originating primarily from the requirement of an active stabilization of the laser frequency to a cavity mode. The main aim of the work presented in this thesis has been to develop a simpler and more robust NICE-OHMS instrumentation without compro-mising the high sensitivity and selectivity of the technique. A compact NICE-OHMS setup based on a fiber laser and a fiber-coupled electro-optic modulator has been constructed. The main advantage of the fiber laser is its narrow free-running linewidth, which significantly simplifies the frequency stabilization procedure. It has been demonstrated, using acetylene and carbon dioxide as pilot species, that the system is capable of detecting relative absorption down to 3 × 10-9 on a Doppler-broadened transition, and sub-Doppler optical phase shift down to 1.6 × 10-10, the latter corresponding to a detection limit of 1 × 10-12 atm of C2H2. Moreover, the potential of dual frequency modulation dispersion spectrometry (DFM-DS), an integral part of NICE-OHMS, for concentration measurements has been assessed. This thesis contributes also to the theoretical description of Doppler-broadened and sub-Doppler NICE-OHMS signals, as well as DFM-DS signals. It has been shown that the concentration of an analyte can be deduced from a Doppler-broadened NICE-OHMS signal detected at an arbitrary and unknown detection phase, provided that a fit of the theoretical lineshape to the experimental data is performed. The influence of optical saturation on Doppler-broadened NICE-OHMS signals has been described theoretically and demonstrated experimentally. In particular, it has been shown that the Doppler-broadened dispersion signal is unaffected by optical saturation in the Doppler limit. An expression for the sub-Doppler optical phase shift, valid for high degrees of saturation, has been derived and verified experimentally up to degrees of saturation of 100.
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Waldén, Pierre, et Erik Aronson. « Spectroscopic characterization of transiting exoplanets : A study of the possibility to detect atmospheres around exoplanets using SIMPLE ». Thesis, Uppsala universitet, Observationell astrofysik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-149020.
Texte intégralRésumé :
This report describes simulations of observations with the near-infrared high-resolution spectrometer SIMPLE that is proposed to the ESO telescope E-ELT. We simulate M4 and G2 stars with transiting Earth-like planets and the goal is to distinguish spectral features originating from the atmosphere of the exoplanet. Noise levels of different magnitudes are added to the simulations and the minimal signal-to-noise required for detection of the atmosphere is estimated. Our conclusion is that detection of atmospheric features looks promising using this setup.
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Neveu, Pascal. « Propagation de lumière dans l'hélium métastable : stockage, amplification, fluctuations et bruit quantique ». Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLN044/document.
Texte intégralRésumé :
Un état quantique de lumière est caractérisé par la statistique de son nombre de photons. Lorsque qu'un champ électromagnétique se propage dans un milieu, ses statistiques peuvent être modifiées, notamment en présence de phénomènes cohérents. Cette thèse s'intéresse expérimentalement et théoriquement à la propagation d'états quantiques de lumière dans une vapeur d'hélium métastable à température ambiante. Dans un premier temps, on étudie la propagation de lumière en présence d'oscillations cohérentes de populations ultrafines et montre qu'elles permettent de stocker efficacement une quadrature spécifique d'un champ lumineux. Néanmoins, ce protocole ne permet pas de stocker les deux quadratures d'un mode du champ électromagnétique, et les conditions de propagation dans le milieu dégradent leurs propriétés statistiques, empêchant son utilisation pour des applications quantiques. Ce travail montre ensuite qu'il est possible de générer des états comprimés à deux modes dans ce même système, par mélange à 4 ondes. Les états fortement comprimés (9 dB) peuvent être générés en exploitant les fortes non-linéarités induites par piégeage cohérent de population via une transition optique, ainsi que par la proximité d'une autre transition optique voisine. Enfin, une dernière partie s'intéresse au transfert de bruit par effet Faraday entre les fluctuations de spin atomique du milieu et les fluctuations de polarisation d'un champ lumineux. L'étude de ces fluctuations par spectroscopie de bruit de spin a mis en évidence des comportements originaux qui pourraient par la suite être utilisés dans d'autres milieuxA quantum state of light is characterized by its statistics of number of photons. These statistics can change in the presence of coherent phenomena. This PhD focuses both experimentally and theoretically on the propagation of quantum states within a room temperature vapor of metastable helium. First, we show that ultranarrow coherent population oscillations allow to efficiently store a specific quadrature of a light wave. Nevertheless, this protocol cannot be use to store the two quadratures of a light field. Indeed, the propagation conditions deteriorates its statistical properties, forbidding its use for quantum application. Secondly, we show that it is possible to generate twomode squeezed states of light in that system. High amplification can be achieved (9 dB), exploiting the strong nonlinearities enabled by coherent population trapping of a transition, and because of the energy level structure. Finally, we study atomic spin noise transfer to light polarization noise via Faraday effect. These fluctuations, probed by spin noise spectroscopy, show original behaviors that may be useful in another systems
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Landi, Giovanni [Verfasser]. « Organic semiconductor material and device characterization by low-frequency noise and admittance spectroscopy of polymer : fullerene solar cells and silicon/organic thin film heterodiodes / Giovanni Landi ». Hagen : Fernuniversität Hagen, 2014. http://d-nb.info/1060847574/34.
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Stock, Stephan Amir [Verfasser], et Sabine [Akademischer Betreuer] Reffert. « Analysis of High-Precision Spectroscopic Data in Search of Exoplanet Signals Close to the Stellar Noise Limit / Stephan Amir Stock ; Betreuer : Sabine Reffert ». Heidelberg : Universitätsbibliothek Heidelberg, 2021. http://d-nb.info/123415210X/34.
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