No description available.

The conventional way of using a nonlinear Fabry-Perot cavity as an optical memory requires a negative pulse input to reset the state of the cavity. The possibility of using positive pulses to turn a system of nonlinear Fabry-Perot cavities on and off is studied and it was found that positive pulse switching is possible in a system of two coupled nonlinear cavities. First, Korpel and Lohmann's proposal of using polarization switching in a single nonlinear birefringent cavity was studied. After a detailed investigation of their proposal it was found that positive pulse switching in a single nonlinear Fabry-Perot cavity is not possible. One of the reasons is that the eigen-polarization states of the output of a nonlinear Fabry-Perot cavity cannot be switched independently. Although it is not possible to switch a single nonlinear Fabry-Perot cavity with positive pulses we were able to use the coupling of the eigen-polarization states to implement other kinds of optical switches which were demonstrated experimentally. The cross-talk effect in a metallic Fabry-Perot cavity was also studied. Next, a steady state model of a system of two coupled nonlinear Fabry-Perot cavities was developed and it was found that positive pulse switching is possible in such a system. The output can be turned on and off either by pulses sent into different cavities or by pulses of different magnitudes sent into one cavity. Finally, the dynamic behavior of the coupled cavities system was modeled by extending Goldstone and Garmire's model of a single cavity with one input to a system of two coupled cavities with two inputs. We verified by numerical calculations that positive pulse switching is also possible in the dynamic regime. / Ph. D.

Desenvolvemos um modelo teórico para tratar a mistura de várias ondas em meios absorvedores saturáveis, considerando a auto-difração de duas ondas incidentes numa grade de população, a qual é induzida no meio não-linear. O modelo foi investigado através de resultados experimentais observados em rubi (Al2O3:Cr3+), alexandrita (BeAl2O4:Cr3+) e GdAlO3: Cr3+. Demonstramos, pela primeira vez, transferência de energia por mistura não degenerada de duas ondas (NDTWM) em alexandrita e GdAlO3: Cr3+. Neste ultimo, também observamos a difração de primeira ordem do feixe forte e medimos a variação de sua intensidade com relação a velocidade de deslocamento da grade. No GdAlO3: Cr3+, medimos o espectro de absorção do estado excitado e o espectro da parte real do índice de refração não-linear em quatro linhas do laser de argônio e na região de 560-620 nm de um laser de corante operando com rodamina 6G. Os resultados indicam uma interação entre pares de cromo no estado excitado, seguida da absorção de um fóton, a qual pode explicar a variação da parte imaginaria n2 com a intensidade, conforme observado experimentalmente. Nós tentamos observar bi-estabilidade óptica em GdAlO3: Cr3+ mas não tivemos êxito, provavelmente por causa de efeitos transversais e também pelo aumento da absorção com a intensidade. Por outro lado, observamos um regime multi-estável numa cavidade Fabry-Perot vazia, onde o meio não-linear é o material usado na fabricação dos espelhos, que no caso foi o ZrO2. Também observamos comportamento multi-estável em filtros de inconel, causado pelo acoplamento termo-óptico entre o filtro e a radiação laser. / We have developed a new approach to deal with multi-wave mixing in saturable absorbing media, by considering the self diffraction of two incident waves in a population grating which is created by them in the nonlinear medium. Wehave also made experimental work on ruby (Al2O3:Cr3+), alexandrite (BeAl2O4:Cr3+) and GdAlO3: Cr3+ in order to compare with our theoretical model. We have demonstrated energy transfer by nearly degenerated two wave mixing (NDTWM) in alexandrite and GdAlO3: Cr3+ for the first time. We measured the intensity of the first order diffracted intense beam as a function of the frequency shift between the incident beams in GdAlO3: Cr3+. For this crystal, we have obtained the spectra of the excited state absorption and the real part of the nonlinear index at four wavelengths of an argon laser and in the range 560-620 nm of a rodamine 6G dye laser. These kinds of spectra had never been reported before in that material. The result seems to support our proposal of an excited chromium pair interaction with an additional photon absorption which can explain the observed variation of the imaginary part of the nonlinear Kerr index with the intensity. We tried to observe optical bistability in GdAlO3: Cr3+ but we were unsuccessful, probably due to strong transverse effects and increasing absorption with the intensity. However we observed multistable regime in empty Fabry-Perot cavities in which the mirrors were made of thin films of ZrO2 deposition. A multistable thermo-optical behavior in inconel filters was also observed.

Depuis quelques années, les matériaux à transition de spin présentant une bistabilité thermique ou photoinduite sont très étudiés en raison des applications futures potentielles pour le stockage de l'information. Dans ce contexte, ce travail a pour objectif la synthèse de nouveaux systèmes bistables du fer (ll). Pour ce faire, deux stratégies ont été utilisées : l'une consiste à augmenter les interactions intramoléculaires en substituant le contre-ion d'un système à transition de spin, l'autre consiste à associer un ligand neutre polydentate à un co-ligand anionique pontant.Dans une première partie, Ia modification du contre-ion a permis l'obtention d'un système discret mononucléaire à base d'un ligand macrocyclique présentant de la bistabilité thermique. Le second système discret est un complexe dinucléaire à base du ligand tmpa (triméthylpyridyl amine] qui a permis de mettre en avant les effets de la substitution du Iigand sur les caractéristiques de la transition de spin.Dans un deuxième temps, nous nous sommes orientés vers la synthèse de systèmes à structures étendues en utilisant des ligands anioniques rigides pontants de type tétracyanométallate [M(CN)4 ]²zassociés au ligand organique 8-aminoquinoléine (aqin). Cette association a conduit à l'obtention de chaînes monodimensionnelles présentant une transition abrupte avec hystérésis.Enfin, pour obtenir des systèmes bi- et tri-dimensionnels, nous avons associé le ligand 4-(2pyridyl)-1,2,4, 4H-triazole (trz-pyJ, potentiellement pontant, aux ligands anioniques [tcpd]L et [Pt(CN]al].Le système [Fe[trz-pyJz[Pt[CNJ4)].3H20 obtenu est un réseau 2D de type Hofmann avec des propriétés magnétiques et photo-magnétiques originales se distinguant par la présence d'une hystérésis cachée révélée par pho to-irradiation. / In recent years, Spin Crossover materials [SCO) with thermal or Iight induced bistability are extensively studied because of their futur potential applications in memory display devices. In this context, the aim of this work is the synthesis of bistable new spin crossover systems based on Fe(ll). Two strategies were used: the first one is to increase the intramolecular interactions by substituting the counter-ion nature in a spin crossover system, the second one is to associate a neutral ligand to a bridging polydentate co-ligand.In rhe ffrst part, the modification of the counter-ion enabled us to obtain a discrete mononuclear system based on macrocycle ligand with thermal bistability. The second discrete system is a dinuclear complex based on tmpa (triimethylpyridyl amine) which led us to study ligand substitution effects of the Spin Cross-Over behaviour.In rhe second part, the aim is the synthesis of extended structures systems by using rigid anionic bridging ligands like tetracyanometallate anions [M[CN)4]2-and the organic ligand quinolin-8-amine. This association allowed to obtain 1D chains with abrupt spin crossover presenting hysteresis.Finally, to synthesise SCO 2D and 3D systems, we have associated the potentially bridging 4-[2pyridyl)-t,2,4,4H-triazole (trz-pyJ ligand to inorganic bridging anions tcpd²- and [Pt[CN)4]²-. The [Fe[trzpy)2(Pt[CN)4]].3H20 system obtained is as Hofmann-like 2D network with novel magnetic and photomagnetic properties with hidden hysteresis revealed by photo-switching.

In addition to the canonical photoreceptors, rods and cones, a novelmelanopsin-expressing retinal ganglion cell (mRGC) was recently discovered.The novel photopigment melanopsin in the human retinahas been shown to express invertebrate-like bistable properties bothin vitro and in vivo. In bistable photopigment systems, light elicitsphotosensory responses and drives photoregeneration of the chromophoreto restore photic responsiveness. These studies have shownthat prior light exposure can modulate the amplitude of subsequentphotic responses of melanopsin.In this thesis, the putative bistability of melanopin in humans isexamined. The bistability was studied using 1) pupillary light reflex(PLR) as a tool, 2) developing a method for quantifying the effectsof lens density for melanopsin-mediated photoreception, and 3) providinga quantitative mathematical framework for modeling bistablepigment systems and non-image forming (NIF) visual system.Exploiting the bistable properties of melanopsin could allow foroptimization of spectral light distribution in experimental, industrial,domestic and clinical phototherapy applications by appropriate useof the photoregenerative effects of long wavelength light.

Une nouvelle famille de porphyrines chirales bridées a été mise au point dans le but d'accéder à des systèmes présentant un processus redox irréversible, lié à une bistabilité conformationnelle, dans le but de les appliquer dans le domaine des mémoires moléculaires. Ces nouvelles porphyrines sont constituées de deux brides ancrées sur les quatre positions meso par des groupes cyclohexyle. Une amine secondaire a été insérée au centre des brides dans le but d'obtenir des métalloporphyrines présentant une seule conformation à l'équilibre pour une longueur de bride, un métal et un degré d'oxydation donnés et pour favoriser un changement conformationnel en fonction du degré d'oxydation d'un métal comme le manganèse. Pour cela, une nouvelle voie de synthèse des porphyrines bridées par pré-fonctionnalisation du dialdéhyde autour de la fonction amine a été conçue. Les porphyrines ont été caractérisées par spectroscopie RMN, spectroscopie UV-Visible et dichroïsme circulaire. Les conformations des bases libres, des complexes de zinc(II) et de nickel(II) ont été déterminées par RMN proton. Pour une longueur de bride de 9 atomes avec une amine secondaire, les conformations des complexes de zinc(II) et de nickel(II) sont respectivement αααα et ααββ. En partant de ce modèle, les complexes de manganèse(II) et de chloromanganèse(III) ont été synthétisés et caractérisés par spectroscopie UV-Visible, dichroïsme circulaire et RMN du carbone 13 afin d'étudier si des changements de conformation en fonction du degré d'oxydation du métal ont lieu. / A new family of chiral bridled porphyrins was designed in order to access systems presenting an irreversible redox process linked to a conformational switch. Such systems could be of high interest in the field of molecular memories. These new porphyrins are made of two bridles anchored to the four macrocycle meso positions through cyclohexyl groups. The first objective is to introduce a secondary amine in the centre of the bridles in order to allow metalloporphyrins with defined bridle length and specific metal with a given oxidation degree to be only under one conformation at equilibrium. The second objective is to favor a conformational switch dependent on the oxidation state of a redox metal such as manganese. To reach these goals, a new porphyrin synthetic pathway was established. The key steps of this new protocol were the synthesis of the bridle built around the central amine with two terminal aldehyde functions required for the macrocyle formation. Porphyrins were studied by NMR, UV-Visible and circular dichroism spectroscopies. The conformations of free base porphyrins, zinc(II) complexes and nickel(II) complexes were determined by 1H NMR. For a bridle with a chain length of 9 atoms including the secondary amine, the zinc(II) complex presents only an αααα conformation and nickel(II) complex an ααββ conformation. From these structural models, manganese(II) and chloromanganese(III) complexes were synthesised and characterised by UV-Visible spectroscopy, circular dichroism and 13C NMR in order to study the possible conformational switches dependent on the Mn redox state.

Desenvolvemos um modelo teórico para tratar a mistura de várias ondas em meios absorvedores saturáveis, considerando a auto-difração de duas ondas incidentes numa grade de população, a qual é induzida no meio não-linear. O modelo foi investigado através de resultados experimentais observados em rubi (Al2O3:Cr3+), alexandrita (BeAl2O4:Cr3+) e GdAlO3: Cr3+. Demonstramos, pela primeira vez, transferência de energia por mistura não degenerada de duas ondas (NDTWM) em alexandrita e GdAlO3: Cr3+. Neste ultimo, também observamos a difração de primeira ordem do feixe forte e medimos a variação de sua intensidade com relação a velocidade de deslocamento da grade. No GdAlO3: Cr3+, medimos o espectro de absorção do estado excitado e o espectro da parte real do índice de refração não-linear em quatro linhas do laser de argônio e na região de 560-620 nm de um laser de corante operando com rodamina 6G. Os resultados indicam uma interação entre pares de cromo no estado excitado, seguida da absorção de um fóton, a qual pode explicar a variação da parte imaginaria n2 com a intensidade, conforme observado experimentalmente. Nós tentamos observar bi-estabilidade óptica em GdAlO3: Cr3+ mas não tivemos êxito, provavelmente por causa de efeitos transversais e também pelo aumento da absorção com a intensidade. Por outro lado, observamos um regime multi-estável numa cavidade Fabry-Perot vazia, onde o meio não-linear é o material usado na fabricação dos espelhos, que no caso foi o ZrO2. Também observamos comportamento multi-estável em filtros de inconel, causado pelo acoplamento termo-óptico entre o filtro e a radiação laser. / We have developed a new approach to deal with multi-wave mixing in saturable absorbing media, by considering the self diffraction of two incident waves in a population grating which is created by them in the nonlinear medium. Wehave also made experimental work on ruby (Al2O3:Cr3+), alexandrite (BeAl2O4:Cr3+) and GdAlO3: Cr3+ in order to compare with our theoretical model. We have demonstrated energy transfer by nearly degenerated two wave mixing (NDTWM) in alexandrite and GdAlO3: Cr3+ for the first time. We measured the intensity of the first order diffracted intense beam as a function of the frequency shift between the incident beams in GdAlO3: Cr3+. For this crystal, we have obtained the spectra of the excited state absorption and the real part of the nonlinear index at four wavelengths of an argon laser and in the range 560-620 nm of a rodamine 6G dye laser. These kinds of spectra had never been reported before in that material. The result seems to support our proposal of an excited chromium pair interaction with an additional photon absorption which can explain the observed variation of the imaginary part of the nonlinear Kerr index with the intensity. We tried to observe optical bistability in GdAlO3: Cr3+ but we were unsuccessful, probably due to strong transverse effects and increasing absorption with the intensity. However we observed multistable regime in empty Fabry-Perot cavities in which the mirrors were made of thin films of ZrO2 deposition. A multistable thermo-optical behavior in inconel filters was also observed.

<p dir="ltr">The ability to change the shape of aerodynamic surfaces is necessary for modern aircraft, both to provide control while performing maneuvers and to meet the conflicting requirements of various flight conditions such as takeoff/landing and level cruise. These shape changes have traditionally been accomplished through the use of various mechanical devices actuating discrete aerodynamic surfaces, for example ailerons and flaps. Such control surfaces and high-lift devices are generally limited to their specific functionality and create surface discontinuities which increase drag and aircraft noise. Broadly speaking, the design and study of morphing wings typically seeks to improve the performance of aircraft by completing one or more of the following objectives: reducing the drag from discontinuities in the aerodynamic surface of the wing by closing hinge gaps and creating smooth transitions, reducing weight and/or mechanical complexity by integrating mechanism functionality into compliant structures that can bear aerodynamic load and maintain shape adaptability, and providing unique or optimal functionality to the aircraft by allowing it to adjust its aerodynamic shape to meet the needs of various flight conditions with conflicting objectives and constraints.</p><p dir="ltr">The concepts proposed in this work represent potential methods for addressing these objectives. In each case, a compliant structure with multiple stable states is embedded into the wing. Exploiting elastic structural instabilities in this way provides the advantage that a structure can be made relatively stiff while still allowing for large deformations. In the first case, the development of a 3D-printable rib with an embedded bistable element creates a truss-like 2D structure that allows for modification of the airfoil. Switching states of the elements changes their local stiffness, and therefore the global stiffness of the system. By optimizing the topology of the airfoil, a passive deflection of the trailing edge can be leveraged to change the camber to leverage different lift characteristics for varying operating conditions. Primary work on this concept has included the construction of multiple experimental demonstrators for validating the concept through static structural and wind tunnel testing. In the second case, a cellular material has been investigated incorporating a bistable unit cell with a sinusoidal arch. This provides a metamaterial that can exhibit large, reversible deformations with as many stable configurations as there are rows in the honeycomb. This metamaterial is incorporated into a beam-like structure which can serve as a spar for a spanwise morphing wing, providing sufficient bending and torsional stiffness, particularly when utilized at the wing tip. Extending and retracting the wing by switching the states of the honeycomb rows provides a significant change to the wing’s induced drag and wing loading, making it ideal for optimal flight in both loitering and cruising conditions. Contributions to this concept have been the development and characterization of the bistable unit cell and honeycomb, as well as the design and analysis of the metabeam and morphing wing concept.</p>

No description available.

En plus des photorécepteurs canoniques traditionnels (bâtonnets etcônes), des cellules ganglionnaires contenant le photopigment mélanopsineont récemment été découverts. Une étude récente de notrelaboratoire a suggéré que, dans la rétine humaine, ce nouveau photopigmentexprime des propriétés bistables similaires à celles notéeschez les invertébrés tant in vitro qu’in vivo. Dans les systèmes dephotopigments bistables, la lumière déclenche une réponse photosensoriellemais permet aussi la régénération du chromophore pourrétablir la réactivité lumineuse du photopigment. Cette dernière étudea montré qu’une exposition lumineuse antérieure peut moduler l’amplitudedes réponses lumineuses de la mélanopsine.L’objectif de ma thèse est d’étudier (1) la bistabilité présumée de lamélanopsine chez l’Homme en utilisant comme outil le réflexe photomoteurpupillaire. Ma thèse comporte aussi 2) le développementd’une technique d’évaluation quantitative des effets du brunissementdu cristallin oculaire sur la photoréception impliquant la mélanopsine;3) le développement d’un modèle mathématique portant sur lefonctionnement des photopigments bistables et du système photiquenon visuel.L’exploitation des propriétés bistables de la mélanopsine et l’utilisationappropriée des effets photorégénérateurs des longueurs d’ondeslumineuses longues pourraient servir dans l’optimisation de la compositionspectrale des applications photothérapeutiques (expérimentales,industrielles, domestiques et cliniques). / In addition to the canonical photoreceptors, rods and cones, a novelmelanopsin-expressing retinal ganglion cell (mRGC) was recently discovered.The novel photopigment melanopsin in the human retinahas been shown to express invertebrate-like bistable properties bothin vitro and in vivo. In bistable photopigment systems, light elicitsphotosensory responses and drives photoregeneration of the chromophoreto restore photic responsiveness. These studies have shownthat prior light exposure can modulate the amplitude of subsequentphotic responses of melanopsin.In this thesis, the putative bistability of melanopin in humans isexamined. The bistability was studied using 1) pupillary light reflex(PLR) as a tool, 2) developing a method for quantifying the effectsof lens density for melanopsin-mediated photoreception, and 3) providinga quantitative mathematical framework for modeling bistablepigment systems and non-image forming (NIF) visual system.Exploiting the bistable properties of melanopsin could allow foroptimization of spectral light distribution in experimental, industrial,domestic and clinical phototherapy applications by appropriate useof the photoregenerative effects of long wavelength light. / Perinteisten fotoreseptorien, sauvasolujen ja tappisolujen, lisäksi verkkokalvoltaon löydetty melanopsiinia sisältäviä gangliosoluja. Fotopigmenttimelanopsiinin on huomattu käyttäytyvän ihmisen verkkokalvollaselkärangattomien eläimien bistabiilin näköjärjestelmän tavoinsekä in vivo- ja in vitro- olosuhteissa. Bistabiileissa fotopigmenttijärjestelmissävalo aiheuttaa sensoristen vasteiden lisäksi kromoforin fogeneraationvastevalmiisen tilaan. Nämä aiemmat tutki-mukset ovatosoittaneet, että aiempi valoaltistus voi moduloida siitä seuraaviamelanopsiinivasteita.Tässä väitöskirjassa melanopsiinin oletettua bistabiiliutta tutkittiinkäyttäen 1) Pupillireaktiota työkaluna, 2) kehittämällä kvantitaviinenmenetelmä mykiöntiheyden vaikutuksiin melanopsiini-fotoreseptiossa,ja 3) kehittäen kvantitatiivisen matemaattisen kehyksen bistabiilien pigmenttijärjestelmien ja ei-visuaalisen näköjärjestelmän mallintamiseen.Melanopsiinin bistabiileita ominaisuuksia on mahdollista optimoidavalon spektrikoostumusta niin tieteellisissä, teollisissa, kotitalouksellisissaja kliinisissä valoterapia sovelluksissa hyväksikäyttämälläpunaisen aallonpituusalueen fotoregeneroivia vaikutuksia.