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1
Munhoz, Fabiana. "Polarization resolved four-wave mixing microscopy : structural and vibrational read-out in molecular media". Aix-Marseille 3, 2010. http://www.theses.fr/2010AIX30062.
Testo completoAbstract (sommario):
La microscopie optique non linéaire polarimétrique offre des nouveaux mécanismes de contraste basés sur les propriétés de symétrie des échantillons. Dans ce travail, nous utilisons le mélange à quatre ondes résolu en polarisation en particulier la diffusion cohérente Raman (CRS), pour sonder les symétries structurales et vibrationnelïes dans les milieux moléculaires. Un modèle théorique a été développé, permettant de déterminer les structures des tenseurs de susceptibilité a partir des considérations de symétrie qui impliquent la structure spatiale du milieu et ses modes vibrationnels. Des résultats expérimentaux sur des échantillons isotropes, cristallins et assemblages biomoléculaires ont été accomplis avec succès. Les mesures polarimétriques à résonance fournissent des informations concernant la symétrie des modes vibrationnels considérés et l'écart aux conditions de la symétrie de Kleinman. Hors résonance nous avons mesuré l'écart de l'isotropie dans des cristaux à symétrie cubique et l'ordre de symétrie et orientation de la distribution moléculaire dans les fibres de collagène. En particulier, nous avons montré que les symétries moléculaires d' ordre supérieur ne peuvent être sondées que par les processus optiques non linéaires d'ordre élevé. Enfin ce travail a démontre que le mélange à quatre ondes résolu en polarisation peut être utilisé comme puissant mécanisme de contraste permettant une sélectivité structurale en imagerie microscopique. Associé à un processus résonant une sélectivitéOne of the greatest challenges in nonlinear optics microscopy is the search for new contrast mechanisms. This is one of the reasons of the increasing interest in polarimetric nonlinear optics in the last couple of decades. In this work we have explored the potential of four-wave mixing in probing vibrational and structural symmetries in molecular media. In particular, we have been concerned with coherent Raman scattering (CRS), either at resonance or not. We have developed a theoretical model allowing to determine the structures of the susceptibility tensors from symmetry considerations, involving both the spatial structure of the medium and the vibration of specific molecular modes. Experimental results on isotropic sample, crystals and biomolecular assemblies were successfully achieved. Polarimetric measurements at resonance provide information on the symmetry of the addressed vibrational modes and on departure from Kleinman symmetry conditions. Nonresonant polarimetric measurements are able to reveal departure from isotropy in cubic crystals and the symmetry order and orientation of molecular distribution in biomolecular assemblies, such as collagen fibers. In particular, we have shown that higher-order molecular symmetries can only be probed by high-order nonlinear optical processes. Finally, this work has demonstrated the great potential of polarimetric four-wave mixing as a powerful contrast mechanism, providing structural selectivity in microscopy imaging. When it is further associated with a resonant process (such as CRS), it provides also chemical selectivity, allowing a complete description of the sample, involving both structural and vibrational symmetries
2
Bioud, Fatma Zohra. "Microscopie de mélange à quatre ondes résolue en polarisation pour sonder l’ordre moléculaire dans les milieux biologiques". Thesis, Aix-Marseille, 2013. http://www.theses.fr/2013AIXM4380.
Testo completoAbstract (sommario):
Nous avons développé une méthodologie basée sur phénomène de mélange à quatre ondre polarimétrique « Four wave Mixing FWM » et son équivalen résonant la diffusion Raman cohérente anti-Stokes (CARS, Coherent Anti-Stokes Raman Scattering) polarimétrique et réalisé des mesures sur des systèmes cristallins, simili biologiques : les membranes cellulaires connues sous le nom de « Multilamellar Vesicles MLV » et des échantillons de biologiques : la myeline, et ce, en variant les polarisations des lasers excitateurs, Pompe et Stokes. Le signal anti-Stokes émis est ensuite analysé afin d’en extraire les ordres 2 et 4 de la fonction de distribution angulaire des molécules actives constituant l’échantillon. Pour cela, plusieurs approches sont explorées telles que des algorithmes d’optimisation ou par décomposition en série de fourrier du signal polarimétrique. Ces multiples approches en traitement du signal permettent d’obtenir de manière rapide les coefficients des fonctions de distribution angulaire recherchées, et ainsi d’avoir des informations sur la symétrie des échantillons imagés, allant jusqu’à l’observation d’une symétrie d’ordre 4. La capacité de la microscopie non linéaire résolue en polarisation à sonder des ordres moléculaires est clairement démontrée et ainsi son intérêt dans l’étude de la relation entre la structure et la fonction de systèmes biologiquesThe capacity to quantify molecular orientational order in tissues is of a great interest since pathologies (skin lesion, neurodegenerative diseases, etc) can induce strong modifications in proteins’ organization. While numerous studies have been undertaken using polarization resolved second order nonlinear optical microscopy which is only specific to non-centrosymmetric organizations, higher order effects have been less explored. Four-wave mixing (FWM) microscopy and its resonant counterpart coherent anti-Stokes Raman scattering (CARS) can be of a great utility as label free diagnosis tools benefiting from less constraining symmetry rules. In this work, we implement incident polarizations tuning in FWM and CARS microscopy to probe molecular order, using a generic method to read-out symmetry information.Fourier analysis of the polarization-resolved FWM/CARS signal processed with an analytical model provides a fast and direct determination of the symmetry orders of the distribution function of the probed molecules. This method does not require a priori knowledge of the organization structure and provides quantitatively its second and fourth order symmetries. We applied this technique on different systems, from crystalline to less organized (multilamellar vesicles and proteins aggregates). We show that this new approach brings additional and more refined information on supra-molecular structures in complex media
3
Petch, Jason Charles. "Resonant four-wave mixing in krypton". Thesis, Imperial College London, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.243502.
Testo completo
4
Meacher, D. R. "Laser bandwidth effects on four-wave mixing". Thesis, University of Oxford, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.329927.
Testo completo
5
Charlton, A. "Degenerate four-wave mixing with pulsed lasers". Thesis, University of Oxford, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.376890.
Testo completo
6
Bray, Mark Edgar. "Four wave mixing in semiconductor laser amplifiers". Thesis, University of Cambridge, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.283929.
Testo completo
7
Canto, Edesly J. "Picosecond degenerate four-wave mixing in semiconductors". Thesis, University of North Texas, 1990. https://digital.library.unt.edu/ark:/67531/metadc798147/.
Testo completoAbstract (sommario):
This study reports on a variety of experimental and theoretical studies conducted in ZnSe, CdTe, and in semiconductor-doped glasses. The transient picosecond degenerate four-wave mixing (DFWM) experiments performed in these II-VI direct-gap semiconductors are part of our efforts to understand the picosecond dynamics of the free-carriers generated via two and three-photon absorption.
8
Kucukkara, Ibrahim. "Electromagnetically induced transparency in four wave mixing scheme". Thesis, Imperial College London, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.398877.
Testo completo
9
Bratfalean, Radu T. "Theory and applications of degenerate four-wave mixing". Thesis, University of Oxford, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.301172.
Testo completo
10
Bottrill, Kyle. "All-optical signal regeneration using four-wave mixing". Thesis, University of Southampton, 2016. https://eprints.soton.ac.uk/405476/.
Testo completoAbstract (sommario):
All-optical signal processing schemes are being studied as promising candidates for adoption in future optical transmission systems, where they are hoped to offer benefits such as ultra-fast signal processing, reduced energy consumption and in some cases, multi-channel processing, supporting the deployment of new techniques such as optical burst switching and software defined networks. The topic of this thesis is the all-optical phase and amplitude regeneration of complex signals using four-wave mixing (FWM). Many schemes for all-optical signal regeneration which have so far been demonstrated expose a signal to some undesirable concomitant distortion during regeneration, grossly limiting their practicability. Therefore, the work in this thesis focuses upon eliminating these undesirable effects and pursuing the development of regenerators possessing more ideal performance. To this end, an amplitude preserving phase regenerator is ?first demonstrated using a phase sensitive amplifier (PSA) which functions through the use of an additional phase harmonic beyond that commonly used. The conclusions of this are extended to show that, given a means to coherently add a large number of phase harmonics of a signal, the phase transfer function of a PSA may be tailored exactly as pleased using a method similar to Fourier analysis. Adoption of an exact solution to degenerate FWM allows for the demonstration of phase preservation in a saturated, pump-degenerate FWM-based amplitude regenerator, enabled by adopting a high pump to signal power ratio. Understanding of the phase noise processes present in this amplitude regenerator leads to an alternative scheme for phase preservation being demonstrated, which functions by predistorting the signal using optical nonlinearities, before amplitude squeezing. This technique is then combined with a novel, single stage, wavelength converting idler-free PSA, to realise a system which is capable of regenerating both the phase and amplitude of a signal, and, by making use of the conjugating nature of both stages, allows for the negation of nonlinearity induced phase distortion between the two stages to realise a system which is greater than the sum of its two parts.
11
Walser, Andreas Markus. "Time-resolved four-wave mixing spectroscopy of gaseous formaldehyde /". Zürich : ETH, 2008. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=18044.
Testo completo
12
Sanches, Piaia Monica. "Femtosecond magneto-optical four-wave mixing in Garnet films". Thesis, Strasbourg, 2014. http://www.theses.fr/2014STRAE024/document.
Testo completoAbstract (sommario):
Un des objectifs du Femtomagnetisme est de contrôler l’aimantation des matériaux avec des impulsions laser femtoseconde. Il a été démontré qu’une réponse magnéto-optique (MO) cohérente a lieu avant la thermalisation des populations de spins dans une configuration pompe-sonde MOKE. Elle résulte du couplage cohérent spin-photon dû à l’interaction spin-orbite. Une description simplifiée de cet effet a été faite en tenant compte d’un système à huit niveaux couplés au champ laser. La cohérence MO est définie par le temps de déphasage dépendent du champ T2MO. Dans ce travail, il est montré que la réponse MO cohérente d’un grenat dopé au bismuth peut être mesurée directement avec différentes configurations de mélange à quatre ondes MO. L’importance de connaître la phase spectrale de l’impulsion pour obtenir T2MO a été étudié. Avec des impulsions de 10fs dans le proche infra-rouge, une mesure de T2MO donne (2.8+/-1)fs, c. à d., du même ordre de grandeur que le temps de déphasage des chargesOne of the goals of Femtomagnetism is to manipulate the magnetization of materials using femtosecond optical pulses. It has been shown in ferromagnetic films that a magneto-optical (MO) coherent response takes place before the thermalization of the spins populations in a pump and probe MOKE experiment. It results from the coherent spin-photon coupling mediated by the spin-orbit interaction. A simplified description of this effect has been made by considering an eight-level system coupled with the laser field. The MO coherence can be defined by the magnetic field dependent dephasing time T2MO. In the present work, it is shown that the coherent MO response of a bismuth-doped garnet can be directly measured in different degenerated MO four-wave mixing configurations. The importance of well-knowing the spectral phase of the pulse to measure T2MO was studied. Using 10fs near infra-red pulses, T2MO was shown to be (2.8+/-1)fs that is of the same order of the charges dephasing time
13
Lloyd, Geraint M. "Four wave mixing techniques and applications in combustion diagnostics". Thesis, University of Oxford, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.363830.
Testo completo
14
Attar, Hameed Abdul-Wahid Ahmid Al. "Four-wave mixing and optical bistability in indium antimonide". Thesis, Heriot-Watt University, 1986. http://hdl.handle.net/10399/1065.
Testo completo
15
SILVA, WILTON LACERDA. "THE FOUR-WAVE MIXING ISSUE IN OPTICAL MULTICHANNEL SYSTEMS". PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 1997. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=8688@1.
Testo completoAbstract (sommario):
CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICONeste trabalho, uma análise do fenômeno de mistura de quatro ondas (FWM) em sistemas ópticos multicanais é apresentada. Inicialmente, uma série de simulações determina as limitações impostas aos sistemas ópticos, sendo adotado um nível máximo de crosstalk permitido. Em seguida, os diversos parâmetros que influenciaram a eficiência da geração de FWM são estudados detalhadamente, com resultados apresentados em forma de gráficos. Nestes últimos, o nível de FWM obtido é especificado em função da potência de entrada por canal, comprimento do enlace, número de canais, presença de amplificadores, número de amplificadores e dispersão cromática da fibra utilizada. Um breve estudo discute a deterioração da qualidade do serviço, causada pro FWM, em redes ópticas. O trabalho se encerra com algumas aplicações que utilizam, de forma favorável, o fenômeno de FWM.
This work adresses the four-wave mixing (FWM) issue in optical multichannel systems. First, some simulations are carried out for specifying which are the optical system limitations coping with a maximum allowed crosstalk level. Next, the different parameters affecting the FWM are throughly studied, with these last pertinent results being graphicallly presented. In these, the obtained FWM levels are specified as a function of the channel input power, link span, channel rumber, presence of amplifiers, number of amplifiers and fiber chromatic dispersion. A concise discussion, concerning the quality of service deterioration on optical networks, due to FWM, is also presented. The work is finally closed by presenting some applications that favorably use the FWM phenomena.
16
Gabel, Allan Harley. "Degenerate four wave mixing in semiconductor doped glass waveguides". Diss., The University of Arizona, 1988. http://hdl.handle.net/10150/184367.
Testo completoAbstract (sommario):
This dissertation begins with a study of some of the linear and nonlinear optical properties of composite materials consisting of CdSₓSe₁₋ₓ microcrystallites embedded in a host glass matrix. These studies investigate changes in absorption, refractive index and nonlinear response time under a variety of experimental conditions. The data demonstrates that this class of materials exhibit: a strong saturation of absorption due to band filling; a large n₂ which also saturates; response times which range from <100ps to many nanoseconds; and a permanent darkening and change of n₂ induced by extended exposure to high energy pulses. These measurements were used to identify the optimum sample of the semiconductor doped glasses to demonstrate an efficient degenerate four-wave mixing process within a planar waveguide. High quality single mode waveguides were fabricated from the semiconductor doped glass by K⁺-ion exchange. Four wave mixing was performed in the waveguide that produced a peak reflectivity of ≅.003, which is 8 orders of magnitude larger than that achieved previously in a similar experiment where CS₂ was used as the nonlinear medium.
17
Thompson, John Russell. "Multiple four-wave mixing processes in single-mode optical fiber". Diss., Georgia Institute of Technology, 1991. http://hdl.handle.net/1853/30955.
Testo completo
18
Williams, R. B. "Degenerate four wave mixing for combustion diagnostics of nitric oxide". Thesis, University of Oxford, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.308746.
Testo completo
19
Tookey, Andrew. "Ultrafast four-wave-mixing in wide-bandgap II-VI semiconductors". Thesis, Heriot-Watt University, 1998. http://hdl.handle.net/10399/1261.
Testo completo
20
Barrett, Graham Robert. "Temporal solutions of the four wave mixing interaction in photorefractives". Thesis, King's College London (University of London), 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.244196.
Testo completo
21
Marciu, Daniela. "Optical Limiting and Degenerate Four-Wave Mixing in Novel Fullerenes". Diss., Virginia Tech, 1999. http://hdl.handle.net/10919/26285.
Testo completoAbstract (sommario):
Two experimental methods, optical limiting and degenerate four-wave mixing, are employed to study the nonlinear optical properties of various novel fullerenes structures. Optical limiting refers to decreased transmittance of a material with increased incident light intensity. Detailed measurements of the wavelength-dependence of fullerene optical limiters have illustrated several key features of reverse saturable absorption. Most important among these is the requirement of weak but non-negligible ground state absorption. We have shown that the optical limiting performance of C₆₀ can be extended into the near infrared range by appropriate modifications of the structure such as higher cage fullerenes or derivatization of the basic C₆₀ molecule. The higher cage fullerene C₇₆ shows improved optical limiting behavior compared to C₆₀, for wavelengths higher than 650 nm, but becomes a weak limiter in the 800 nm range. C₈₄, even at high concentrations in [alpha]-chloronaphthalene, does not reach the good performance of C₆₀, but instead shows weak optical limiting in the 800 nm range.
We also demonstrate that by attaching various groups to the C₆₀ molecule, we can extend the optical limiting performance in the near infrared regime. The C₆₀ derivatives studied, (C₆₀ cyclic ketone, C₆₀ secondary amine, C₆₀CHC₆H₄CO₂H, and C₆₀C₄H₄(CH₃)CH₂O₂C(CH₂)CO₂H), have a similar characteristic: the attached groups cause a symmetry-breaking of the C₆₀ sphere and, therefore, there are new allowed transitions that appear as absorption features up to 750 nm. The optical limiting measurements show that these materials, even for low input energies, have an exceptionally strong optical limiting response in the 640 to 750 nm spectral region. For wavelengths higher than 800 nm, however, they become transparent and no optical limiting is observed. Excited state absorption cross-sections obtained from analysis of the optical limiting data reveal that the C₆₀ derivatives have a maximum triplet-triplet absorption cross-section at 700 nm, which is shifted from the 750 nm value for the C₆₀ molecule. For the first time, optical limiting measurements are performed on five separate C₈₄ isomers. These intriguing results show that the optical limiting behavior is strongly dependent on the cage symmetry. It is also found that the most abundant isomer does not have the strongest optical limiting performance, but is in fact one of the weaker optical limiters of the isomers isolated so far.
The endohedral metallofullerenes are a unique class of fullerene materials and consist of one or more metal atoms encapsulated inside the buckyball cage. An important characteristic of these materials is the charge-transfer from the dopant atoms to the fullerene cage, which has a high electron affinity. The charge-transfer is similar to the optical excitation in a material, but although the electrons are placed in the lowest unoccupied molecular orbital (LUMO), there are no holes produced in the highest occupied molecular orbital (HOMO). This is an important analogy, since it has been previously shown that optical excitation enhances the nonlinear optical properties of a material. The nonresonant degenerate four-wave mixing experiments performed on the endohedral metallofullerene Er₂@C₈₂, at 1064 nm, show that the third order nonlinear susceptibility value is increased by orders of magnitude relative to the empty cage fullerenes, thus, confirming the charge-transfer process from the encapsulated atoms to the fullerene cage. We obtain a value [gamma]xyyx(3)( [omega]; [omega], [omega], [omega])= 8.65 × 10⁻³² esu for the molecular second order hyperpolarizability, which is almost three orders of magnitude larger than the values reported in literature for an empty cage fullerene.Ph. D.
22
Gattobigio, Giovanni Luca. "Manipulation of a Large Magneto-Optical Trap:application to Four-Wave Mixing". Phd thesis, Université de Nice Sophia-Antipolis, 2008. http://tel.archives-ouvertes.fr/tel-00312718.
Testo completoAbstract (sommario):
Dans cette thèse, nous présentons une recherche expérimentale détaillée des lois caract érisant la taille et la densité atomique de grands pièges magnéto-optiques contenant typiquement 10^10 atomes. Il est bien connu que les interactions induites par laser, produites par la diffusion multiple, y constituent la limitation principale à l'obtention de densités atomiques élevées. Pour contourner cette limite, nous avons réalisé un piège magnéto-optique 'noir' combiné un piège dipolaire. Les forces de répulsion assistées par la lumière ont ainsi pu être considérablement réduites et une augmentation de près de deux ordres des grandeur sur le densité (jusqu'à 10^12 atm/cm^3) a été corrélativement observée. Nous avons proposé également un modèle qualitatif pour rendre compte de la densité atomique (et également pour la taille) o`u nous avons introduit les interactions mécaniques induites par les photons du laser repompeur quand son épaisseur optique devient importante. Ce travail fait partie d'un projet de recherche qui vise à terme à observer la localisation d'Anderson de la lumière dans des nuages d'atomes froids, mais pour laquelle des densités de l'ordre (10^13-10^14 atm/cm^3) sont requises. Pour des densités inférieures, des mécanismes de gain peuvent toutefois être mis à profit pour amplifier des modes pre-localisés. Nous avons, ainsi, mis en place une technique pompe-sonde pour la création d'un gain dans l'échantillon atomique. La configuration des pompes a autorisé l'observation du signal de mélange a quatre ondes. Une analyse détaillée de ses propriétés et de ses caractéristiques a été présentée. En particulier, une asymétrie rouge-bleu dans le spectre, pour des intensités élevées des faisceaux pompes, a été mise en évidence. Cette asymétrie a pu tre expliquée en tenant compte du regroupement des atomes dans les noeuds ou dans les ventres de l'onde stationnaire des faisceaux de pompe.
23
Memon, Muhammad Irfan. "Optical injection locking and four-wave mixing in semiconductor ring lasers". Thesis, University of Bristol, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.535213.
Testo completo
24
Darwish, Ali Mohamed. "Wavelength conversion by four wave mixing in passive InGaAsP/InP waveguides". Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/38839.
Testo completo
25
Signorini, Stefano. "Intermodal four wave mixing for heralded single photon sources in silicon". Doctoral thesis, Università degli studi di Trento, 2019. https://hdl.handle.net/11572/368239.
Testo completoAbstract (sommario):
High order waveguide modes are nowadays of great interest for the development of new functionalities in photonics. Because of this, efficient mode couplers are required.
In this thesis a new strategy for mode coupling is investigated, based on the interference arising from two coherent tilted beams superimposed in a star-coupler.
Handling the high order modes allows to explore new processes within the photonics platform, as the intermodal four wave mixing. Intermodal four wave mixing is a new nonlinear optical process in waveguide, and it is here demonstrated on a silicon chip. Via intermodal four wave mixing it is possible to achieve a large and tunable frequency conversion, with the generation of photons spanning from the near to the mid infrared. The broadband operation of this process is of interest for the field of quantum photonics. Single photon sources are the main building block of quantum applications, and they need to be pure and efficient. Via intermodal four wave mixing, it is here demonstrated the generation of single photons above 2000 nm heralded by the idler at 1260 nm. Thanks to the discrete band phase matching of this
nonlinear process, high purity single photons without narrow band spectral filters are demonstrated. Intermodal four wave mixing enables a new class of classical and
quantum sources, with unprecedent flexibility and spectral tunability. This process is particularly useful for the developing field of mid infrared photonics, where a
viable integrated source of light is still missing.
26
Signorini, Stefano. "Intermodal four wave mixing for heralded single photon sources in silicon". Doctoral thesis, University of Trento, 2019. http://eprints-phd.biblio.unitn.it/3713/1/PhdThesis_Signorini.pdf.
Testo completoAbstract (sommario):
High order waveguide modes are nowadays of great interest for the development of new functionalities in photonics. Because of this, efficient mode couplers are required.
In this thesis a new strategy for mode coupling is investigated, based on the interference arising from two coherent tilted beams superimposed in a star-coupler.
Handling the high order modes allows to explore new processes within the photonics platform, as the intermodal four wave mixing. Intermodal four wave mixing is a new nonlinear optical process in waveguide, and it is here demonstrated on a silicon chip. Via intermodal four wave mixing it is possible to achieve a large and tunable frequency conversion, with the generation of photons spanning from the near to the mid infrared. The broadband operation of this process is of interest for the field of quantum photonics. Single photon sources are the main building block of quantum applications, and they need to be pure and efficient. Via intermodal four wave mixing, it is here demonstrated the generation of single photons above 2000 nm heralded by the idler at 1260 nm. Thanks to the discrete band phase matching of this
nonlinear process, high purity single photons without narrow band spectral filters are demonstrated. Intermodal four wave mixing enables a new class of classical and
quantum sources, with unprecedent flexibility and spectral tunability. This process is particularly useful for the developing field of mid infrared photonics, where a
viable integrated source of light is still missing.
27
Smith, P. G. R. "Spectroscopic and imaging aspects of degenerate four-wave mixing for combustion diagnostics". Thesis, University of Oxford, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239399.
Testo completo
28
Kaczmarek, M. "Dynamics of resonant degenerate four-wave mixing and applications in gaseous media". Thesis, University of Oxford, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.291286.
Testo completo
29
Gattobigio, Giovanni Luca. "Manipulation of a large magneto-optical trap : application to four-wave mixing". Nice, 2008. http://www.theses.fr/2008NICE4022.
Testo completo
30
SIMBULA, ANGELICA. "Microring Resonators as Integrated Sources of Nonclassical States of Light". Doctoral thesis, Università degli studi di Pavia, 2017. http://hdl.handle.net/11571/1203285.
Testo completoAbstract (sommario):
The experimental work that is reported in the thesis explores some properties and possible uses of silicon microring resonators as integrated sources of non-classical states of light, based on the enhancement of non-linear effect of four-wave mixing (FWM).The experimental work that is reported in the thesis explores some properties and possible uses of silicon microring resonators as integrated sources of non-classical states of light, based on the enhancement of non-linear effect of four-wave mixing (FWM).
31
Offer, Rachel Frances. "Four-wave mixing in rubidium vapour with structured light and an external cavity". Thesis, University of Strathclyde, 2018. http://digitool.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=30381.
Testo completo
32
Goldberg, Benjamin M. "Electric Field Measurements in Non-Equilibrium ElectricDischarge Plasmas Using Picosecond Four-Wave Mixing". The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1449236861.
Testo completo
33
Donaldson, Paul Murray. "Two dimenstional infrared four wave mixing spectroscopy of simple molecules, peptides and proteins". Thesis, Imperial College London, 2008. http://hdl.handle.net/10044/1/1245.
Testo completoAbstract (sommario):
In this thesis, measurements of electron-vibration-vibration two dimensional infrared (EVV 2DIR) spectra are demonstrated for the first time from aliphatic, aromatic and amide containing compounds. Bioanalytical applications of EVV 2DIR spectroscopy are explored and the first EVV 2DIR measurements on proteins reported. Operational protocols for collecting EVV 2DIR spectra are described and it is shown for the case of benzene Fermi resonances how excitation pulse ordering can be used to isolate different EVV coherence pathways, giving signals that report on several aspects of a molecule’s electrical and mechanical anharmonicity. Experimental spectra are compared with first principles simulations and in general found to be in good agreement with one another. It is shown that inter-pulse delays can substantially clean up frequency domain spectra and for the range of compounds studied, the 2DIR spectra are significantly decongested compared with their 1D infrared and Raman counterparts. EVV 2DIR coherence lifetime measurements are reported and applied to a range of simple organic compounds. Measurements of exponential dephasing, nonexponential dephasing and quantum beating are demonstrated, with the exponential decays used to accurately measure vibrational linewidths and the quantum beats to measure line splittings.
34
Monti, Federico. "Time sampling using four-wave mixing to measure the dynamics of semiconductor nanolasers". Electronic Thesis or Diss., université Paris-Saclay, 2024. http://www.theses.fr/2024UPASP026.
Testo completoAbstract (sommario):
Les nanolasers PhC suscitent de plus en plus d'attention en raison de leur capacité unique à manipuler et à confiner la lumière à une très petite échelle. Leur empreinte réduite et leur seuil bas en font des candidats idéaux pour la réalisation de connexions optiques, répondant ainsi à la demande croissante en matière de vitesse de transmission des données et de consommation d'énergie. De plus, leur géométrie singulière permet de contrôler leurs propriétés d'émission spontanée. Cela révèle l'unicité des nanolasers PhC d'un point de vue fondamental, soulignant leur potentiel à servir de sujets de recherche novateurs dans l'interaction lumière-matière. Malgré ces avantages, une caractérisation de leur émission et de leurs propriétés dynamiques fait toujours défaut, en raison des limitations actuelles des capacités de détection aux longueurs d'onde infrarouges.Dans cette thèse, j'ai développé une technique de détection à porte temporelle basée sur FWM, pour mesurer la réponse ultra-rapide des nanolasers 1D. En étudiant attentivement l'interaction entre les non-linéarités et la dispersion, il a été possible d'atteindre une sensibilité élevée de quelques photons et une résolution de 2 ps. Des améliorations supplémentaires de la sensibilité, jusqu'à moins d'une détection de photon, sont prévues en utilisant des puissances de pompe plus élevées. Cela peut ouvrir la voie à l'étude des statistiques des photons et des effets quantiques au cœur du régime quantique.Les profils des nanolasers 1D présentent un début très rapide de l'émission et une décroissance longue, compatible avec un facteur β de 0,12 et une durée de vie du photon de 20 ps. Une nouvelle approche pour obtenir les valeurs de ces deux paramètres contrôlant la dynamique du laser a été développée : elles ont été directement extraites de la réponse ultra-rapide des nanolasers, au lieu de se baser uniquement sur des mesures à l'état stationnaire telles que la courbe S, qui, dans de nombreux cas, peuvent conduire à des estimations inexactes en raison de l'interdépendance de ces paramètres. La réponse dynamique des nanolasers 1D est compatible avec une vitesse maximale de modulation d'environ 30 GHz, répondant à l'exigence de sources laser ultra-compactes à faible seuil pour les circuits intégrés photoniques et les communications optiques.La haute sensibilité et résolution de la technique nous ont permis de mesurer, pour la première fois à notre connaissance, une conversion de longueur d'onde adiabatique de photons avec un décalage de longueur d'onde aussi important que 1,2 nm. Cela montre le potentiel de la technique dans l'étude des dynamiques ultra-rapides aux longueurs d'onde NIRPhC nanolasers are receiving more and more attention due to their unique capacity to manipulate and confine light at a very small scale. Their small footprint and low thresholds make them ideal candidates for realizing optical interconnects, thus addressing the increasing demands for data transmission speed and power consumption. Moreover, their singular geometry enables the control of their spontaneous emission properties. This reveals PhC nanolasers' uniqueness from a fundamental point of view, highlighting their potential to serve as candidates for novel research in light-matter interaction. Despite these advantages, a characterization of their emission and their dynamical properties is still missing, due to the current limitations of the detection capabilities at infrared wavelengths.In this thesis, I have developed a time gating detection technique based on FWM, to measure the ultra fast response of 1D nanolasers. By carefully studying the interplay between nonlinearities and dispersion, it was possible to reach a high sensitivity of a few photons and a resolution of 2 ps. Further improvements in sensitivity, down to less than a photon detection, is predicted by employing higher gate powers. This can open the way to study photon statistics and quantum effects deep in the quantum regime.The profiles of 1D nanolasers feature a very fast onset of the emission and a long decay, compatible with a β factor of 0.12 and a photon lifetime of 20 ps. A novel approach to obtaining the values of these two parameters controlling laser dynamics has been developed: they have been directly retrieved from the%The manner in which these two parameters controlling laser dynamics have been obtained constitutes a novel approach, as they have been directly retrieved from theultra-fast response of nanolasers, instead of solely relying on steady state measurements such as the S curve, which, in many cases, can lead to inaccurate estimations due to the interdependence of these parameters. The dynamical response of 1D nanolasers is compatible with a maximum modulation speed of around 30 GHz, fullfiling the requirement for low threshold ultra compact laser sources for photonic integrated circuits and optical communications.The high sensitivity and resolution of the technique allowed us to measure for the first time, to the best of our knowledge, an adiabatic wavelength conversion of photons with a wavelength shift as large as 1.2 nm. This shows the potential of the technique in studying ultra fast dynamics at NIR wavelengths
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Embrey, Christopher. "Controlling local quantum fluctuations of light using four-wave mixing in an atomic vapour". Thesis, University of Birmingham, 2016. http://etheses.bham.ac.uk//id/eprint/6440/.
Testo completoAbstract (sommario):
The spatial character of the noise on a light field affects its usefulness for imaging. Multi-spatial-mode (MSM) squeezed light has noise below the quantum noise limit in multiple spatial modes, and can be used for super resolution imaging. The generation of such light has long been an experimental goal within the field of quantum optics. This work introduces the theory behind the generation of squeezed light, and its measurement using a homodyne detector. A four-wave mixing process in a rubidium 85 vapour is used to experimentally generate squeezed light. The properties of this squeezed light are investigated, through the use of homodyne detection with a bichromatic LO. This thesis further investigates how the squeezed quadrature changes from amplitude to phase over a range of 40 MHz. The MSM nature of a squeezed light field is directly investigated. The field is shown to contain at least 75 squeezed spatial modes in the frequency domain, each squeezed at a level of up to -2.5 dB. This thesis develops techniques to measure the spatial character of noise on a light field in the time domain. These are promising techniques for the analysis of the MSM nature of a squeezed light in the time domain.
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Turnbull, Matthew. "Multi-spatial-mode quadrature squeezing from four-wave mixing in a hot atomic vapour". Thesis, University of Birmingham, 2014. http://etheses.bham.ac.uk//id/eprint/5148/.
Testo completoAbstract (sommario):
Noise suppression across multiple spatial modes of a light field would serve to improve the field's imaging capabilities and allow it to act as a more effective carrier of quantum information. This thesis describes a scheme that utilises a nonlinear process (four wave mixing (4WM)) in Rubidium 85 in order to generate a single beam of light that demonstrates sub quantum noise limit (QNL) quadrature fluctuations of up to -4dB across a multitude of spatial modes simultaneously. Included is a description of sub-QNL (squeezed) light, followed by a breakdown of how this 4WM arrangement generates the desired quantum noise suppression. Analysis has been performed that displays explicitly how the phase matching arrangement that maximises the noise suppression differs from that which optimises the efficiency of the process. This consideration is crucial to understanding why the setup achieves the levels of squeezing observed despite the presence of a strong absorption feature. Finally, the multi-spatial-mode nature of the generated squeezing is observed directly via homodyne detection using local oscillators with a range of transverse profiles. These profiles select the mode of the signal to be analysed and as such the ability to detect squeezing using a range of them demonstrates its presence across all of these modes simultaneously.
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Ostatnicky, Tomas. "Model calculation of four-wave mixing polarization and dynamics in bulk and confined semiconductors". Université Louis Pasteur (Strasbourg) (1971-2008), 2005. https://publication-theses.unistra.fr/public/theses_doctorat/2005/OSTATNICKY_Tomas_2005.pdf.
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Haidar, El-Abed. "Analysis of the modification of four-wave mixing phase matching by stimulated Brillouin scattering". Thesis, The University of Sydney, 2017. http://hdl.handle.net/2123/17062.
Testo completoAbstract (sommario):
My thesis is a theoretical and numerical investigation of the feasibility of enhancing the four wave mixing bandwidth by tuning the phase matching condition via stimulated Brillouin scattering. This technique was experimentally demonstrated in 2013 by introducing the amplitude and phase optical gain/loss frequency responses of stimulated Brillouin scattering (SBS) pump and Stokes waves onto the FWM pump or the FWM signal. Both SBS amplitude and phase responses originate from modifying the refractive index of the optical fibre while the FWM interaction takes place. As a result the FWM phase-matching condition and hence the signal gain can be flexibly controlled. The theoretical investigation was carried out with both processes considered separately. In this thesis, we show that with modest optical power, exponential gain is achievable for normal dispersion, which leads to a gain bandwidth which is comparable in size to that for anomalous dispersion without SBS. This is equivalent to a sign change of the nonlinear contribution to the phase matching condition. However the method is limited by SBS-induced power variations and by the need to limit the SBS power levels. The thesis is illustrated while using highly nonlinear silica fibre, a well-known platform for efficient gain in telecommunications as an example. Our results can be equally applied to other materials and to other geometries, for example that of chalcogenide photonic chips, which is an interesting and exciting platform for all-optical signal processing devices. This platform is considered in Chapter 3.
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Siebert, Torsten Uwe. "Four-wave mixing techniques applied to the investigation of non-adiabatic dynamics in polyatomic molecules". Doctoral thesis, [S.l. : s.n.], 2002. http://deposit.ddb.de/cgi-bin/dokserv?idn=966017331.
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Babocsi, Krisztina. "Characterization of II-VI semiconductor nanostructures by low wavenumber raman- and four-wave-mixing spectroscopy". Doctoral thesis, [S.l. : s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=975014862.
Testo completo
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Walker, D. J. W. "Spectroscopic studies of four wave mixing and its application to velocimetry and combustion species detection". Thesis, University of Oxford, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.389041.
Testo completo
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Kuebler, Stephen Michael. "Studies of the third-order nonlinear optical properties of materials by degenerate four-wave mixing". Thesis, University of Oxford, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.389007.
Testo completo
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Filion, Benoît. "Wavelength converters based on four-wave mixing in semiconductor optical amplifiers for advanced modulation formats". Doctoral thesis, Université Laval, 2016. http://hdl.handle.net/20.500.11794/26796.
Testo completoAbstract (sommario):
Les convertisseurs de longueur d’onde sont essentiels pour la réalisation de réseaux de communications optiques à routage en longueur d’onde. Dans la littérature, les convertisseurs de longueur d’onde basés sur le mélange à quatre ondes dans les amplificateurs optiques à semi-conducteur constituent une solution extrêmement intéressante, et ce, en raison de leurs nombreuses caractéristiques nécessaires à l’implémentation de tels réseaux de communications. Avec l’émergence des systèmes commerciaux de détection cohérente, ainsi qu’avec les récentes avancées dans le domaine du traitement de signal numérique, il est impératif d’évaluer la performance des convertisseurs de longueur d’onde, et ce, dans le contexte des formats de modulation avancés. Les objectifs de cette thèse sont : 1) d’étudier la faisabilité des convertisseurs de longueur d’onde basés sur le mélange à quatre ondes dans les amplificateurs optiques à semi-conducteur pour les formats de modulation avancés et 2) de proposer une technique basée sur le traitement de signal numérique afin d’améliorer leur performance. En premier lieu, une étude expérimentale de la conversion de longueur d’onde de formats de modulation d’amplitude en quadrature (quadrature amplitude modulation - QAM) est réalisée. En particulier, la conversion de longueur d’onde de signaux 16-QAM à 16 Gbaud et 64-QAM à 5 Gbaud dans un amplificateur optique à semi-conducteur commercial est réalisée sur toute la bande C. Les résultats démontrent qu’en raison des distorsions non-linéaires induites sur le signal converti, le point d’opération optimal du convertisseur de longueur d’onde est différent de celui obtenu lors de la conversion de longueur d’onde de formats de modulation en intensité. En effet, dans le contexte des formats de modulation avancés, c’est le compromis entre la puissance du signal converti et les non-linéarités induites qui détermine le point d’opération optimal du convertisseur de longueur d’onde. Les récepteurs cohérents permettent l’utilisation de techniques de traitement de signal numérique afin de compenser la détérioration du signal transmis suite à sa détection. Afin de mettre à profit les nouvelles possibilités offertes par le traitement de signal numérique, une technique numérique de post-compensation des distorsions induites sur le signal converti, basée sur une analyse petit-signal des équations gouvernant la dynamique du gain à l’intérieur des amplificateurs optiques à semi-conducteur, est développée. L’efficacité de cette technique est démontrée à l’aide de simulations numériques et de mesures expérimentales de conversion de longueur d’onde de signaux 16-QAM à 10 Gbaud et 64-QAM à 5 Gbaud. Cette méthode permet d’améliorer de façon significative les performances du convertisseur de longueur d’onde, et ce, principalement pour les formats de modulation avancés d’ordre supérieur tel que 64-QAM. Finalement, une étude expérimentale exhaustive de la technique de post-compensation des distorsions induites sur le signal converti est effectuée pour des signaux 64-QAM. Les résultats démontrent que, même en présence d’un signal à bruité à l’entrée du convertisseur de longueur d’onde, la technique proposée améliore toujours la qualité du signal reçu. De plus, une étude du point d’opération optimal du convertisseur de longueur d’onde est effectuée et démontre que celui-ci varie en fonction des pertes optiques suivant la conversion de longueur d’onde. Dans un réseau de communication optique à routage en longueur d’onde, le signal est susceptible de passer par plusieurs étages de conversion de longueur d’onde. Pour cette raison, l’efficacité de la technique de post-compensation est démontrée, et ce pour la première fois dans la littérature, pour deux étages successifs de conversion de longueur d’onde de signaux 64-QAM à 5 Gbaud. Les résultats de cette thèse montrent que les convertisseurs de longueur d’ondes basés sur le mélange à quatre ondes dans les amplificateurs optiques à semi-conducteur, utilisés en conjonction avec des techniques de traitement de signal numérique, constituent une technologie extrêmement prometteuse pour les réseaux de communications optiques modernes à routage en longueur d’onde.Wavelength converters are essential building blocks of future all-optical wavelength-routed optical networks. Wavelength converters based on four-wave mixing in semiconductor optical amplifiers have been proposed since they possess many of the features required for the implementation of such networks. In the literature, they have been extensively studied in the context of direct detection optical communication systems. With the recent emergence of commercial coherent systems together with the advances in digital signal processing, there is an imperative need to study the performance of wavelength converters for advanced modulation formats. The objective of this thesis is to investigate the feasibility of wavelength converters based on four-wave mixing in semiconductor optical amplifiers for advanced modulation formats and subsequently propose a digital signal processing technique that aims to improve their performance. An experimental investigation of m-ary quadrature amplitude modulation (QAM) wavelength conversion is first performed. In particular, wideband wavelength conversion of 10 Gbaud 16-QAM and, for the first time, 5 Gbaud 64-QAM signals is successfully achieved over the whole C-band using a commercial semiconductor optical amplifier. The results show that the induced nonlinear distortions on the wavelength converted signal lead to a different optimal wavelength converter operating condition compared to wavelength conversion of intensity modulation formats. For wavelength conversion of advanced modulation formats, the tradeoff between the wavelength converted signal power and the nonlinearities dictates the optimal wavelength converters operating condition. The digital signal processing capabilities of coherent receivers renders possible the compensation of the signal impairments in the digital domain after detection. Making use of this, a digital post-compensation technique based on a small-signal analysis of the equations governing the gain dynamics of semiconductor optical amplifiers is developed in order to mitigate the nonlinear distortions imposed on the wavelength converted signal. The proof of concept is realized both via numerical simulations and experimental measurements of 10 Gbaud 16-QAM and 5 Gbaud 64-QAM: the post-compensation technique significantly improve the wavelength converter especially in the case of high-order advanced modulation formats such as 64-QAM. Finally, a thorough experimental investigation of the post-compensation technique performance for 5 Gbaud 64-QAM wavelength conversion is done. The results indicate that the signal quality is still improved even in the presence of a noisy signal at the wavelength converter input. Furthermore, it is shown that the optimal wavelength converter operating condition varies upon the amount of optical loss that follows. In a wavelength-routed optical network, the signal will likely pass through multiple wavelength conversion stages. The experimental investigation is extended to cascaded wavelength conversion stages and, for the first time, dual stage wavelength conversion of 5 Gbaud 64-QAM signal is performed. In this context, the proposed post-compensation technique still successfully improves the wavelength converter performance. The results of this thesis strongly suggest that wavelength converters based on four-wave mixing in semiconductor optical amplifiers, together with the use of digital signal processing techniques, is a promising candidate for advanced modulation formats wavelength conversion in future wavelength routed optical networks.
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McGinnis, Brian Patrick. "Four-wave mixing and the study of optical nonlinearities in semiconductors and semiconductor quantum dots". Diss., The University of Arizona, 1989. http://hdl.handle.net/10150/184890.
Testo completoAbstract (sommario):
This dissertation describes the study of various nonlinear optical effects in both bulk and quantum-confined semiconductors. Transverse effects in increasing absorption optical bistability are considered in bulk CdS for both single beam and wave mixing geometries. Measurement of the temporal response of BiI₃ quantum dots is described using degenerate four-wave mixing and explained theoretically. Finally, the experimental techniques developed to measure the one- and two-photon absorption coefficients of CdS quantum dots in glass are described along with the latest theoretical description and interpretation of the experimental spectra. The basic theory of increasing absorption optical bistability is presented along with experimental observation of this effect in CdS at low temperature. Transverse effects in increasing absorption optical bistability were observed in single beam experiments with CdS at low temperatures. The ring structures observed experimentally are explained theoretically. Degenerate four-wave mixing performed with this nonlinearity is theoretically shown to produce new scattering orders compared with a standard Kerr analysis. Experimental observation of these new scattering orders is presented. The temporal response of the nonlinearity in a solution of BiI₃ quantum dots in acetonitrile is determined using degenerate four-wave mixing. The independent contributions to the phase-conjugate signal are determined for both of the spatial gratings induced in the solution. The observed temporal responses indicated that a thermal mechanism was responsible for the nonlinearity. A theoretical analysis based on a thermal nonlinearity is presented which provides good agreement with the observed responses. The experimental techniques necessary to measure the one- and two-photon absorption coefficients of CdS quantum dots are described. The resultant measurements of quantum dot samples with microcrystallites ranging from 3.6 to 10.8 nm in diameter indicate no splitting of the energy levels associated with the hole. Theoretical spectra indicate this can be partially explained by the inclusion of Coulombic effects of the charged electron-hole pair.
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Islam, Md Samiul. "Coherent ultrafast spectroscopy of excitons in Van der Waals materials". Electronic Thesis or Diss., Strasbourg, 2024. http://www.theses.fr/2024STRAE011.
Testo completoAbstract (sommario):
Dans cette thèse, basée sur un développement original de microscopie de mélange à quatre ondesultrarapide, la première mesure directe de la dynamique de cohérence excitonique dans le disulfurede rhénium a été obtenue. Ces résultats ont démontré une robustesse unique de la cohérenceexcitonique par rapport à d'autres matériaux dichalcogénures de métaux de transition(TMD). Le potentiel de contrôle des propriétés intrinsèques des excitons dans les matériaux van der Waals (vdW) a été exploré dans des assemblages bidimensionnels innovants. En particulier, l'impact du graphène sur l'environnement excitonique d'une hétérostructure et sur les propriétés dynamiques de ces excitons a été étudié. Enfin, une avancée significative vers la compréhension et l'ingénierie des propriétés optiques des défauts émetteurs de photons uniques dans le nitrure de bore hexagonal (hBN) a été réaliséeIn this thesis, based on an original development of ultrafast four wave mixing microscopy, the firstdirect measurement of excitonic coherence dynamics in rhenium disulfide was obtained. Theseresults demonstrated a unique robustness of excitonic coherence compared to other Transition metal dichalcogenide (TMD) materials. The potential for controlling the intrinsic properties of excitons in van der Waals (vdW) materials was explored in innovative two-dimensional assemblies. In particular, the impact of graphene in the excitonic environment of a heterostructure on the dynamic properties of these excitons has been investigated. Finally, a significant step towards understanding and engineering the optical properties of single photon emitting defects in hBN has been achieved
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KARAGULEFF, CHRIS. "DEGENERATE FOUR WAVE MIXING IN THIN FILM OPTICAL WAVEGUIDES (NONLINEAR OPTICS, INTEGRATED, PHASE CONJUGATION, SIGNAL PROCESSING)". Diss., The University of Arizona, 1985. http://hdl.handle.net/10150/187908.
Testo completoAbstract (sommario):
The incentive for conducting Degenerate Four Wave Mixing (DFWM) within guided wave devices is two-fold: (1) By coupling the optical beams into guided wave devices, the optical power densities can be increased orders of magnitude due to the tight confinement of the beams. Such an increase in power density means a concomitant increase in conversion efficiency of the signal beam. (2) The potential signal processing applications of DFWM (logic gates, switching, correlation/convolution), particularly for ultra-fast serial processing, would be better exploited, and adjoined to existing integrated circuit technology, by such an integrated optic/guided wave approach. In this dissertation we describe experiments and present data confirming the presence of DFWM within a planar glass thin film with carbon disulphide as the nonlinear cover medium. Optical pulses from a Q-switched, frequency doubled Nd:YAG laser are coupled into the glass film. The nonlinear polarization required to produce the desired conjugate signal is generated within the CS₂ by the evanescent tails of the guided input beams as they probe the nonlinear cover medium. The signals measured agree well with theory, but because they were so small in magnitude, signal-to noise ratios were small due to stray background radiation scattering from beamsplitters and other associated optics. Additionally, recent studies (Jain & Lind, 1983) indicate nonlinear responses in semiconductor (CdS/Se) doped glasses, commercially available as color glass filters, that are orders of magnitude higher than corresponding nonlinearities within CS₂, in addition to possessing subnanosecond response times. We have performed experiments upon such glasses in an effort to fabricate nonlinear optical waveguides within them via ion-exchange techniques. We have successfully fabricated single mode planar guides, but they are currently too lossy to allow demonstration of any guided wave nonlinearities. Also, we describe experiments in which we have measured (bulk) DFWM grating lifetimes with greater precision than previously reported. Results indicate a fast (20 to 50 pico-seconds, depending on the particular glass) electronic response, superimposed upon, but clearly distinguishable from, a slower (10's of nanoseconds) thermal response.
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Patel, Meena. "Numerical study of non-linear spectroscopy and four-wave-mixing in two and multi-level atoms". Thesis, Cape Peninsula University of Technology, 2017. http://hdl.handle.net/20.500.11838/2623.
Testo completoAbstract (sommario):
Thesis (MTech (Electrical Engineering))--Cape Peninsula University of Technology, 2018.In this research, we undertake a numerical study of the interaction between laser beams and two as well as multi-level atoms. The main aim of this research is to obtain a deeper understanding of laser-atom interactions and non-linear processes such as optical four-wave mixing. This work will supplement experiments to be conducted by other members of the group, who are involved in generating entangled photons via four-wave mixing in cold rubidium atoms. We begin by performing a basic study of the interaction between laser beams and two-level atoms as an aid to gain knowledge of numerical techniques, as well as an understanding of the physics behind light-atom interactions. We make use of a semi-classical approach to describe the system where the atoms are treated quantum mechanically and the laser beams are treated classically. We study the interaction between atoms and laser beams using the density matrix operator and Maxwell's equations respectively. By solving the optical Bloch equations for two-level atoms we examine the atomic populations and coherences and present plots of the density matrix elements as a function of time. The e ects of various parameters such as laser intensity, detuning and laser modulation have been tested. The behaviour of the laser beam as it propagates through the atomic sample is also studied. This is determined by Maxwell's equation where the atomic polarization is estimated from the coherence terms of the density matrix elements.
French South African Institute of Technology National Research Foundation
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Kölle, Andreas [Verfasser]. "Coherent Phenomena in Four-Wave Mixing via a Rydberg State in Thermal Vapor of Rubidium / Andreas Kölle". München : Verlag Dr. Hut, 2015. http://d-nb.info/106770809X/34.
Testo completo
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Namboodiri, Vinu V. [Verfasser]. "Femtosecond Time-Resolved Four-Wave Mixing Applied to the Investigation of Excited State Dynamics / Vinu V. Namboodiri". Bremen : IRC-Library, Information Resource Center der Jacobs University Bremen, 2010. http://d-nb.info/1035033917/34.
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Hamilton, James Patrick. "Vibrationally enhanced infrared four wave mixing". 1994. http://catalog.hathitrust.org/api/volumes/oclc/31627052.html.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--University of Wisconsin--Madison, 1994.Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 275-283).