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We report a critical narrowing of resonances of a driven potential well, when their eigenfrequencies approach the edge of the continuum. The resonances also obtain unusual sharp-peak shapes at the continuum boundary. The situation can be realized for the electromagnetic wave propagating across the dielectric thin films with a periodically modulated interface(s). We show the general phenomenon semi-analytically on a simplified model of a driven quantum potential well, also by rigorous numerical analysis of Maxwell equations for the wave propagation across the thin film with a modulated interface(s). We justify the phenomenon experimentally, by the measurements of light reflection from the dielectric thin film deposited on a periodically modulated surface. The narrow and sharp-peak resonances can be used for an efficient narrow-band frequency- and spatial filtering of light.

International audience; We present an analytical and numerical study of the possibility of existence of surface localized modes, the so-called Tamm states, in a one-dimensional (1D) comb-like phononic crystal (PnC). The structure is made out of periodic array of stubs of lengths d2grafted along a waveguide and separated from each other by a tube of length d1. We show the existence of surface modes for the semi-infinite structure. In particular, when one considers two complementary semi-infinite systems obtained by cutting the infinite one into two parts, we obtain one surface mode per gap induced by the surface of the two complementary systems. Furthermore, we demonstrate that these surface modes can be detected from the maxima and minima of the transmission spectrum, when the finite structure is grafted vertically along a homogeneous acoustic waveguide. That means that one can observe experimentally this type of modes for acoustic waves in slender tubes. These results may find many practical applications in noise control and highly sensitive PnC sensors. © 2021 Elsevier Ltd. All rights reserved.

The authors solve the problem of estimating the best rotation aligning two sets of corresponding vectors (also known as Wahba's problem or point cloud registration). The proposed method is among the fastest methods reported in recent literatures, moreover it is robust to noise, accurate and simpler than most other methods. It is based on solving the linear equations derived from the formulation of the problem in Euclidean Geometric Algebra. The authors show its efficiency in two applications: the as-rigid-as-possible (ARAP) surface modelling and the more smooth rotation enhanced ARAP mesh animation which is the only method capable of deforming surface modes with quality of tetrahedral models. Mesh deformation is a key technique in games, automated construction and robotics. The ARAP technique along with its improved variants, although have been extensively studied, can still not be achieved efficiently. Linear geometric algebra based rotor solution proposed in this study gives another perspective of the kernel problem. This, however, not only improves the real performance of the three-dimensional mesh deformation, but also provides a brand new computationally efficient solution to the Wahba's problem and point cloud registration, which has been closely related to the automation science and engineering.

This thesis focuses on topological insulators and their surface states. Topology is a field in mathematics which focuses on the conservation of the relations of points within a geometric object under smooth deformations of the material. It can be used to find nontrivial properties of the electronic bands of an insulating material. At a boundary of a topologically nontrivial material and a trivial one, the collective electronic band gap must go to zero to account for the change in the topological phase. This is the defining property which separates topological insulators from regular ones. Topological insulators have a topological phase in which they have conductive channels on their edges or surfaces, which often have a spin based direction and are required to travel without resistance. This allows for interesting applications ranging from LASERs to supercomputers. In the first part, the theoretical background of electronic band theory and topological materials are examined. The second part introduces the transfer matrix method, in which the material is divided into layers, and connected to adjacent layers by the transfer matrix. Also, topological models are introduced in a logical order where the latter is derived from the former and their edge states and their properties are solved using the transfer matrix method. In the last part the surface states of the four band 3D BHZ-model are solved using the transfer matrix method as introduced earlier. In this way the versatility and ease of the transfer matrix becomes apparent.

Acoustic bubbles are known to allow a contactless and localized action on a surrounding body, as for example in ultrasound therapies or for engineering applications. These bubbles are often encountered as more or less dense groups, called bubble clouds. The behavior of such clouds are driven by acoustic and fluid interactions. The work presented in this dissertation aims at studying the streaming flow induced by such oscillating bubbles as well as the interactions undergone by a bubble couple. Under specific conditions on the size of the bubbles and the acoustic pressure amplitude they are submitted to, a bubble interface can demonstrate shape oscillations. Such deformations give rise to a slow mean flow around the bubble: the so-called microstreaming. A recent theoretical approach is used to understand the diversity of microstreaming patterns that are observed experimentally around bubbles trapped in a resonant water tank. It is shown that the cross-like patterns (large scale action) are linked to self interaction of the main triggered mode and that lobe-like patterns (local action) are associated to the cross-interaction between the breathing mode and the parametrically excited one.The study of a large variety of bubble couples is achieved through the use of a bi-frequency acoustic levitation chamber. Bubbles are maintained at controlled distances in an infinite fluid. Such a technique allows the quantification of the secondary radiation force acting on each bubble, their spherical or nonspherical oscillations, the acoustic coupling at the ultrasonic time scale and the fluid flow they generate. It is shown that the triggering of nonspherical oscillations induce an additional hydrodynamic force which modifies the bubble pair equilibrium. The inversion of the secondary radiation force is evidenced when the bubbles sufficiently attract and migrate to a specific equilibrium location in the trapping field. At this location, the presence of shape modes has been shown to be responsible for bouncing between the bubbles. The acoustic coupling is also studied. Two regimes are evidenced: either the bubbles are both smaller than the resonance size for the chosen excitation frequency and hence the coupling is constructive or they are greater than this resonance size and hence the coupling is destructive. While nonspherical oscillations do not seem to have a huge impact on this coupling, they are at the origin of a large scale hydrodynamic interaction. In this case, the shear stress induced in the bulk is quantified, and appears greater than the threshold required to induce biological effects on cell membranes., Les microbulles de gaz sont des agents physiques permettant une redistribution dans leur voisinage de l’énergie ultrasonore. Dans des applications médicales ou industrielles, elles permettent entre autre la perméabilisation de membrane cellulaire, le nettoyage de surface, l’optimisation de réactions chimiques ... Ces bulles sont généralement rencontrées sous forme d’ensembles plus ou moins denses. Le comportement de ces groupes, ou nuages, de bulles est piloté par différentes interactions, acoustiques ou fluidiques. La compréhension d’un nuage de bulles nécessite d’étudier dans un premier temps un couple de bulles, considéré alors comme une brique élémentaire de ce nuage. Les travaux présentés dans ce mémoire ont pour objectifs d’étudier les couplages acoustiques et fluidiques gouvernant le comportement d’un couple de bulles. Dans un premier temps, le comportement d’une bulle unique est étudié. Sous certaines conditions de taille et de pression acoustique, son interface peut osciller selon des modes non-sphériques. De telles déformations permettent la mise en place d’un écoulement lent et localisé autour des bulles : le microstreaming. Une nouvelle approche théorique, confrontée à des données expérimentales, montre que les motifs de l’écoulement induit varient en fonction de l’interaction modale prédominante, et peuvent permettre une action localisée (motifs en lobes confinés autour de la bulle) ou à plus grande échelle (motifs en croix). Dans un second temps, l’analyse est étendue à un couple de bulle. Pour cela un dispositif expérimental original est proposé, afin de piéger deux bulles à distance contrôlée, loin de toute frontière, dans une chambre acoustique résonante bi-fréquentielle. Ce dispositif permet de quantifier aussi bien la force de radiation secondaire à laquelle les bulles sont soumises, leurs déformations sphériques et non-sphériques, le couplage acoustique à l’échelle ultrasonore et les écoulements induits. Les travaux présentés ici montrent l’influence d’oscillations non-sphériques sur la force de radiation secondaire et la possible inversion de cette force pour des distances inter-bulles faibles. Pour une fréquence d’excitation donnée, le couplage acoustique est constructif ou destructif si les deux bulles du couple sont respectivement sous-résonantes ou sur-résonantes. Les oscillations non-sphériques sont sources d’un couplage significatif uniquement lorsque les deux bulles sont presque en contact. En revanche, les écoulements qui leurs sont associés peuvent interagir à plus grande échelle. Une quantification des contraintes générées dans le milieu par ces écoulements est réalisée, et semblent suffisantes pour induire l’ouverture temporaire de membranes biologiques.

We investigate both theoretically and experimentally the properties of electromagnetic waves propagation and localization in periodic and quasi-periodic stub structures of Fibonacci type. Each block constituting the Fibonacci sequence (FS) is composed of an horizontal segment and a vertical stub. The origin of the primary and secondary gaps shown in such systems is discussed. The behaviors and scattering properties of the electromagnetic modes are studied in two geometries, when the FS is inserted horizontally between two semi-infinite waveguides or grafted vertically along a guide. Typical properties of the Fibonacci systems such as the fragmentation of the frequency spectrum, the self-similarity following a scaling law are analyzed and discussed. It is found that certain modes inside these two geometries decrease according to a power law rather than an exponential law and the localization of these modes displays the property of self-similarity around the central gap frequency of the periodic structure where the quasi-periodicity is most effective. Also, the eigenmodes of the FS of different generation order are studied depending on the boundary conditions imposed on its extremities. It is shown that both geometries provide complementary information on the localization of the different modes inside the FS. In particular, in addition to bulk modes, some localized modes induced by both extremities of the system exhibit different behaviors depending on which surface they are localized. The theory is carried out using the Green&rsquo, s function approach through an analysis of the dispersion relation, transmission coefficient and electric field distribution through such finite structures. The theoretical findings are in good agreement with the experimental results performed by measuring in the radio-frequency range the transmission along a waveguide in which the FS is inserted horizontally or grafted vertically.

The Gent–McWilliams parameterization is commonly used in global ocean models to model the advective component of tracer transport effected by unresolved mesoscale eddies. The vertical structure of the transfer coefficient in this parameterization is studied using data from a 0.1° resolution global ocean‐ice simulation. The vertical structure is found to be well approximated by a baroclinic mode structure with no flow at the bottom, though horizontal anisotropy is crucial for obtaining a good fit. This vertical structure is motivated by reference to the vertical structure of mesoscale eddy velocity and density anomalies, which are also diagnosed from the data.

Microbubbles find use in several domains, one of them being medical ultrasound applications. Different characteristics of those bubbles such as their acoustic resonance or their destructive effect during inertial cavitation can be exploited. Another phenomenon induced around acoustically excited bubbles is microstreaming, that means a relatively slow mean flow with respect to the fast bubble oscillations. Microstreaming and its associated shear stresses are commonly agreed to play a role in the permeabilization of cell membranes, a detailed understanding of the induced flows is however missing. To acquire basic physical knowledge, this work focuses on the characterization of streaming induced around an air bubble in water, more precisely around a single acoustically trapped and excited, nonspherically oscillating bubble. The experimental part consists of two steps. First, the bubble dynamics, in particular the triggered shape mode and the orientation of the bubble have to be controlled. For this, the use of bubble coalescence proves to be an adequate method. In a second step, the microstreaming is recorded in parallel to bubble dynamics. This allows to correlate the obtained streaming patterns to the respective shape oscillations. The large number of obtained pattern types can be classified, in particular with respect to the mode number and bubble size. A close investigation of the bubble dynamics allows furthermore deducing the important physical mechanisms which lead to such a variety of streaming patterns. In order to confirm the experimental findings, an analytical model has been developed. It is based upon time-averaged second-order fluid mechanics equations and the experimentally obtained bubble dynamics serves as input parameters. Supplementary to the microstreaming work, this manuscript contains a short section on directed jetting of contrast agent microbubbles, which might appear at high acoustic driving. The impact of those microjets on cell membranes presents another mechanism made responsible for the permeabilization of cell membranes.; Des bulles micrométriques sont utilisées dans divers domaines, notamment dans des applications médicales basées sur les ultrasons. Il est possible d’exploiter différents effets des bulles, comme par exemple leur résonance acoustique ou leur effet destructeur en cavitation inertielle. Un autre mécanisme exploitable est la génération de micro-écoulements, appelé microstreaming, induits autour d’une bulle. Ces écoulements sont relativement lents par rapport aux oscillations rapides de la bulle. Le microstreaming et les contraintes de cisaillement associées jouent un rôle important dans la perméabilisation d’une membrane cellulaire, mais il manque encore une compréhension détaillée de l’écoulement induit. Afin d’améliorer la compréhension des phénomènes physiques, ce travail se concentre sur les écoulements induits autour d’une bulle d’air dans piégée et excitée acoustiquement dans de l’eau et oscillante en modes de surface. La partie expérimentale se décompose de deux étapes. Dans un premier temps, il est nécessaire de contrôler la dynamique de la bulle, en particulier ses modes de surface et son orientation. Ceci est réalisé par coalescence entre deux bulles. Dans un second temps, le microstreaming est généré et enregistré simultanément à la dynamique de bulle. De cette manière il est possible de corréler les motifs d'écoulement aux oscillations de la bulle. Le grand nombre de motifs obtenus peut être classé selon le mode dominant et la taille de la bulle. Une étude plus détaillée de la dynamique de bulle permet de déduire les paramètres importants qui mènent à une telle variété de motifs de microstreaming. Afin de confirmer les résultats expérimentaux, un modèle analytique a été développé. Il est basé sur les équations de la mécanique des fluides de deuxième ordre et moyennées en temps, la dynamique d'interface de la bulle obtenue expérimentalement sert de donnée d’entrée au modèle. Ce manuscrit contient en supplément une section sur la génération de microjets par l'implosion d'agents de contraste. Ces jets peuvent apparaître en cas d’excitation acoustique suffisamment élevée. L’impact de ces jets sur parois présente un autre mécanisme responsable de la perméabilisation de membranes cellulaires.

Microbubbles find use in several domains, one of them being medical ultrasound applications. Different characteristics of those bubbles such as their acoustic resonance or their destructive effect during inertial cavitation can be exploited. Another phenomenon induced around acoustically excited bubbles is microstreaming, that means a relatively slow mean flow with respect to the fast bubble oscillations. Microstreaming and its associated shear stresses are commonly agreed to play a role in the permeabilization of cell membranes, a detailed understanding of the induced flows is however missing. To acquire basic physical knowledge, this work focuses on the characterization of streaming induced around an air bubble in water, more precisely around a single acoustically trapped and excited, nonspherically oscillating bubble. The experimental part consists of two steps. First, the bubble dynamics, in particular the triggered shape mode and the orientation of the bubble have to be controlled. For this, the use of bubble coalescence proves to be an adequate method. In a second step, the microstreaming is recorded in parallel to bubble dynamics. This allows to correlate the obtained streaming patterns to the respective shape oscillations. The large number of obtained pattern types can be classified, in particular with respect to the mode number and bubble size. A close investigation of the bubble dynamics allows furthermore deducing the important physical mechanisms which lead to such a variety of streaming patterns. In order to confirm the experimental findings, an analytical model has been developed. It is based upon time-averaged second-order fluid mechanics equations and the experimentally obtained bubble dynamics serves as input parameters. Supplementary to the microstreaming work, this manuscript contains a short section on directed jetting of contrast agent microbubbles, which might appear at high acoustic driving. The impact of those microjets on cell membranes presents another mechanism made responsible for the permeabilization of cell membranes., Des bulles micrométriques sont utilisées dans divers domaines, notamment dans des applications médicales basées sur les ultrasons. Il est possible d’exploiter différents effets des bulles, comme par exemple leur résonance acoustique ou leur effet destructeur en cavitation inertielle. Un autre mécanisme exploitable est la génération de micro-écoulements, appelé microstreaming, induits autour d’une bulle. Ces écoulements sont relativement lents par rapport aux oscillations rapides de la bulle. Le microstreaming et les contraintes de cisaillement associées jouent un rôle important dans la perméabilisation d’une membrane cellulaire, mais il manque encore une compréhension détaillée de l’écoulement induit. Afin d’améliorer la compréhension des phénomènes physiques, ce travail se concentre sur les écoulements induits autour d’une bulle d’air dans piégée et excitée acoustiquement dans de l’eau et oscillante en modes de surface. La partie expérimentale se décompose de deux étapes. Dans un premier temps, il est nécessaire de contrôler la dynamique de la bulle, en particulier ses modes de surface et son orientation. Ceci est réalisé par coalescence entre deux bulles. Dans un second temps, le microstreaming est généré et enregistré simultanément à la dynamique de bulle. De cette manière il est possible de corréler les motifs d'écoulement aux oscillations de la bulle. Le grand nombre de motifs obtenus peut être classé selon le mode dominant et la taille de la bulle. Une étude plus détaillée de la dynamique de bulle permet de déduire les paramètres importants qui mènent à une telle variété de motifs de microstreaming. Afin de confirmer les résultats expérimentaux, un modèle analytique a été développé. Il est basé sur les équations de la mécanique des fluides de deuxième ordre et moyennées en temps, la dynamique d'interface de la bulle obtenue expérimentalement sert de donnée d’entrée au modèle. Ce manuscrit contient en supplément une section sur la génération de microjets par l'implosion d'agents de contraste. Ces jets peuvent apparaître en cas d’excitation acoustique suffisamment élevée. L’impact de ces jets sur parois présente un autre mécanisme responsable de la perméabilisation de membranes cellulaires.

Birim hücresinde farklı boyutlu elemanlara sahip yapılar, yüksek simetrili olanlara göre daha büyük bant genişliklerine, iletim spektrumunda daha zengin karakteristiklere, düşük geri yansıma kayıplarına sahip oldukları için son zamanlarda fotonikte yeni nesil aygıt tasarımlarında yaygın şekilde kullanılmaktadır. Bu tez çalışmasında dönme simetrisi azaltılmış periyodik yapılarda asimetrik iletim özelliği, yüzey modları ve yavaş ışık karakteristiği incelenmiştir. Ayrıca aperiyodik olan kuazi kristallerin yüksek olan dönel simetrisi kırılarak kavite yapısı ve yüzey dalga kılavuzları tasarlanmıştır. Optik sinyali bir yönde iletirken ters yönde yansıtarak yapının diğer tarafına ulaşmasını engelleyen optik diyotlar gelişmiş fotonik uygulamalarında kullanılmaya başlanmıştır. Tezin ilk bölümünde, telekom dalgaboyunda geniş bantlı asimetrik iletim özelliğinin yanında ışığı farklı kırınım mertebelerine ayıran fotonik kristal yapı tasarlanmıştır. Silikon malzemeden oluşan farklı yarıçaplı dielektrik silindirler kullanılarak hetero yapılı tasarlanan kırınım ızgarası ışığın geliş açısına oldukça toleranslıdır. Tasarım gelen ışığı +x yönünde %73 oranında iletebilirken, zıt yön olan –x yönünde ise ışığı belli frekanslarda %99'lara kadar yansıtabilmektedir. Ayrıca fotonik kristal ızgara yapısı ileri yönde gelen dalgayı başarılı şekilde kırınım mertebelerine bölmektedir. Farklı frekanslar yapı tarafından farklı kırınım derecelerine ayrılmaktadır. Gösterdiği bu özellikler sayesinde tasarlanan kristal yapı spektrometre alanında kullanım için uygun bir adaydır. Tezin üçüncü bölümünde ise düşük simetrili periyodik yapılarda frekans seçici ve yavaşlatılmış yüzey Bloch dalgaların yönlü iletiminin kontrolü çalışılmıştır. Bunun için kare örgülü periyodik yapıya ikincil saçıcı elemanlar eklenmiş ve sadece yüzeyde yer alan ikincil silindirlerin konumları modifiye edilerek yüzey modun frekansının yanı sıra, ilerleme hızı ve ilerleme yönü de kolayca kontrol edilmiştir. Dizilim açısının düşük değerlerinde yüzeyin grup indisi 237'ye kadar yükselmiştir. Yüzeye tutunan dalgalar indis güdümlü olduğu için dizilimsel değişiklik elektik alan dağılımının farklılaşmasına sebep olmuştur. Böylece yapının etkin kırılma indisi değişerek yüzey mod frekansın modifiye edilmesini sağlamıştır. Bu özelliklerinin yanı sıra bant diyagramında ortaya çıkan yüzey modların negatif eğime sahip olmalarını ters yönlü iletimin mümkün olduğunu göstermiştir. Düşük dizilim açılarında ışık her iki yönde birden ilerlerken, dizilim açısı arttıkça geri yönlü iletim baskın hale gelmektedir. Yüzeyde kolayca modifiye edilebilen yavaş ışık sayesinde tasarım, güneş pillerinde, sensör uygulamalarında ve ışın ayırıcı dalga kılavuzu olarak interferometrelerde kullanılabilir. Tezin son bölümünde ise sekizgen simetrili kuazi kristallerin yüksek olan dönel simetrisi düşürülerek kavite etkisinde ve yüzey modlarda yüksek simetrili olan standart yapıya göre üstün özellikler sergilemesi sağlanmıştır. Kuazi kristalde kavite modlarının frekansı, mod alanları ve kalite faktörleri kontrol edilmiştir. Yüzeyde meydana getirilen modifikasyon bu dizilimlerde de yüzey dalgaların elde edilmesini sağlamıştır. Yüzeyde yer alan silindirlerin büyüklük ve konum değişimi sayesinde frekans ayarlaması mümkün hale gelmiştir., Recently in new generation photonic devices, the designs having elements with different sizes in the unit cell are widely used in photonics, since they have larger bandwidths, richer characteristics in the transmission spectrum, lower back reflection losses than those with high symmetry. In this thesis, asymmetric transmission properties, surface modes, and slow light characteristics are examined in the periodic structures with reduced rotational symmetry. In addition, cavity structure and surface waveguides are designed by breaking the high rotational symmetry of quasicrystals. The optical diodes are used in advanced photonics applications that prevent the optical signal to reach the other side of the structure. In the first part of the thesis, in addition to the broadband feature of the asymmetric transmission at the telecom wavelength, the photonic crystal structure has been designed to separate the light into different diffraction orders. The diffraction grating, which is designed in a heterogeneous manner using dielectric cylinders with different radii of silicon material, is very tolerant of the incident angle of the light wave. The design can transmit the light in the direction of +x by 73%, while the photonic crystal diffraction grating can reflect light at certain frequencies up to 99% in the opposite direction. In addition, the grating structure successfully divides the forward wave into the diffraction orders. The crystal structure designed with these features is a suitable candidate for use in the field of the spectrometer. In the third part of the thesis, control of the directional transmission of frequency selective and decelerated surface Bloch waves in low symmetric periodic structures is studied. For this purpose, additional elements have been added to the periodic structure and only the positions of the cylinders on the surface have been modified, as well as the frequency of the surface mode, the group velocity and the direction of propagation have been easily controlled. At the low values of the orientation angle, the group index of the surface increased to the value of 237. Since the waves that are attached to the surface are index guided, the position change of the rods causes the electric field distribution to vary. The changing effective refractive index of the structure allows the modulation of the surface frequency. Also, the negative slope of the surface modes appearing in the band diagram shows that backward transmission is possible on the structure surface. For the low orientation angles, the light travels in both directions, while the backward propagation becomes more dominant as the angle of orientation increases. Owing to the slow light property of the surface modes which can be easily modified on the surface, the design can be used in solar cells, sensor applications, and interferometers as a beam splitter waveguide. In the last part of the thesis, the high rotational symmetry of the octagonal quasicrystals is reduced to enhance the performance of the design in terms of cavity effect and surface modes. In quasicrystal, frequency, mode areas, and quality factors of the cavity modes are easily controlled. The surface-induced modification provides surface waves in this arrangement. Thanks to the size and position change of the cylinders located on the surface, frequency adjustment has become possible.

A theoretical study is made for the bulk and surface plasmon-polaritons in one-dimensional semi-infinite layered semiconductor photonic crystals with graphene interlayers. The retarded dispersion relations are calculated in a general way and applied to two cases, depending on whether a graphene sheet is present or absent at the first interface of the semi-infinite structure. We apply the result to doped GaAs as the constituent material, considering the layers to be arranged in a periodic fashion with alternating layer thicknesses. Both s- and p-polarized modes are evaluated with the effects of retardation on the polaritons being included in the general expressions. Simplifications, particularly for the surface modes, are studied for the case when retardation effects are small. Through numerical examples, we illustrate the important role of the graphene sheets in modifying the plasmon-polariton properties (focusing on the region near the bulk plasma frequency). A strong dependence on the mode polarization is found

International audience; Conventional techniques for food and water quality control and environmental monitoring in general have a number of drawbacks. Below we propose a label-free highly accurate analytical technique for multiplex detection of biomarkers based on the analysis of propagation of Bloch waves on the surface of a photonic crystal. The technique can be used to measure molecular and cell affinity interactions in real time by recording critical and excitation angles of the surface wave on the surface of a photonic crystal. Based on the analysis of photonic crystal surface modes, we elaborated a protocol for the detection of the exotoxin A of Pseudomonas aeruginosa and the heat-labile toxin LT of Escherichia coli. The protocol exploits detection of affinity interactions between antigens pumped through a microfluidic cell and detector antibodies conjugated to the chemically activated silica chip. The proposed technique is highly sensitive, cheap and less time-consuming in comparison with surface plasmon resonance.

[EN] The dynamics of continuous systems that exhibit circular or spherical symmetry like drops, bubbles or some macromolecules, under the influence of some external excitation, develop surface patters that are hard to predict in most practical situations. In the particular case of acoustically driven microbubbles (ultrasound contrast agent), the study of the behavior of the bubble shell requires complex modeling even for describe the most simple oscillation patterns. Furthermore, due to the smallness of the spatio-temporal scale of the problem, an experimental approach requires expensive hardware setup. Despite the complexity of the particular physical problem, the basic dynamical features of some continuous physical systems can be captured by simple models of coupled oscillators. In this work we consider an analogy between a shelled-gas bubble cavitating under the action of an acoustic field and a discrete mechanical system. Thus, we present a theoretical and experimental study of the spatial instabilities of a circular ring of coupled pendulums parametrically driven by a vertical harmonic force. The system is capable of wave propagation and exhibit nonlinearities and dispersion, so manifest rich dynamics: normal oscillation modes (breathing, dipole, quadrupole...) and localized patterns of different types (breathers and kinks) witch are predicted by finite-differences numerical solutions and observed experimentally. On the basis of this analogy, the oscillation patterns and localized modes observed experimentally in acoustically driven bubbles are interpreted and discussed., [ES] La dinámica de sistemas continuos que muestran simetría circular o esférica como gotas, burbujas, o algunas macromoléculas, bajo la influencia de una excitación externa desarrollan patrones de superficie que en muchas situaciones prácticas son difíciles de predecir. En el caso particular de una microburbuja bajo la acción de un campo acústico (agente de contraste ultrasónico), el estudio de la dinámica de la burbuja requiere un complejo modelado incluso para describir los modos de oscilación más simples. Además, debido a la pequeña escala espacio-temporal del problema, el estudio experimental requiere un hardware extremadamente sofisticado y costoso. Por otro lado, la dinámica de muchos sistemas complejos continuos puede ser modelada por medio de agrupaciones de osciladores acoplados. Así, en este trabajo se considera una analogía entre la microburbuja cavitando bajo la acción del campo acústico y un sistema de discreto de osciladores mecánicos excitados paramétricamente. De esta manera, se presenta un estudio teórico y experimental de las inestabilidades de un anillo de péndulos acoplados paramétricamente excitados por una fuerza armónica vertical. Así, el sistema presenta propagación de ondas, exhibiendo no linealidad y dispersión, por lo que una rica dinámica se observa: modos propios, como el modo radial o “breathing mode”, dipolar, cuadripolar, etc. y estructuras localizadas como breathers o modos intrínsecos localizados, kinks, etc. Todos ellos han sido observados experimentalmente y numéricamente obtenidos mediante diferencias finitas. A la vista de los resultados, el presente experimento es un excelente banco de pruebas para el estudio de sistemas no lineales en un curso de grado o máster. La presencia de forzamiento paramétrico y pérdidas, así como la interacción entre linealidad y dispersión provoca que el sistema presente la rica dinámica el amplio abanico de fenómenos estudiados de una manera muy visual e intuitiva para el estudiante., The authors acknowledge financial support from the Spanish Ministry of Science and Innovation and European Union FEDER through project FIS2011-29731-C02-02.

We report the first experimental observation of an excitonic optical Tamm state supported at the interface between a periodic multilayer dielectric structure and an organic dye-doped polymer layer. The existence of such states is enabledby the metal-like optical properties of the excitonic layer based on aggregated dye molecules. Experimentally determined dispersion curves, together with simulated data, including field profiles, allow us to identify the nature of these new modes. Our results demonstrate the potential of organic excitonic materials as a powerful means to control light at the nanoscale, off ering the prospect of a new alternative photonic building block for nanophotonics designs based on molecular materials.

This is a very comprehensive review article on electromagnetic metamaterials, written with one of the foremost experts in the field, S.A. Ramakrishna. Our collaboration is supported by a grant from the french-indian funding body IFCPAR CEFIPRA entitled 'Plasmonic properties of checkerboard metallic structures and films' (2008-2012); International audience; Newly discovered metamaterials have opened new vistas for better control of light via negative refraction, whereby light refracts in the “wrong” manner. These are dielectric and metallic composite materials structured at subwavelength lengthscales. Their building blocks consist of local resonators such as conducting thin bars and split rings driving the material parameters such as the dielectric permittivity and magnetic permeability to negative (complex) values. Combined together, these structural elements can bring about a (complex valued) negative effective refractive index for the Snell–Descartes law and result in negative refraction of radiation. Negative refractive index materials can support a host of surface plasmon states for both polarizations of light. This makes possible unique effects such as imaging with subwavelength image resolution through the Pendry–Veselago slab lens. Other geometries have also been investigated, such as cylindrical or spherical lenses that enable a magnification of images with subwavelength resolution. Superlenses of three-fold (equilateral triangle), four-fold (square) and six-fold (hexagonal) geometry allow for multiple images, respectively two, three, and five. Generalization to rectangular and triangular checkerboards consisting of alternating cells of positive and negative refractive index represents a very singular situation in which the density of modes diverges at the corners, with an infinity of images. Sine-cosecant anisotropic heterogeneous square and triangular checkerboards can be respectively mapped onto three-dimensional cubic and icosahedral corner lenses consisting of alternating positive and negative refractive regions. All such systems with corners between negative and positive refractive media display very singular behavior with the local density of states becoming infinitely large at the corner, in the limit of no dissipation. We investigate all of these, using the unifying viewpoint of transformation optics.

International audience; The efficient and reliable computation of guided modes in photonic crystal wave-guides is of great importance for designing optical devices. Transparent boundary conditions based on Dirichlet-to-Neumann operators allow for an exact computation of well-confined modes and modes close to the band edge in the sense that no modelling error is introduced. The well-known super-cell method, on the other hand, introduces a modelling error which may become prohibitively large for guided modes that are not well-confined. The Dirichlet-to-Neumann transparent boundary conditions are, however, not applicable for all frequencies as they are not uniquely defined and their computation is unstable for a countable set of frequencies that correspond to so called Dirichlet eigenvalues. In this work we describe how to overcome this theoretical difficulty introducing Robin-to-Robin transparent boundary conditions whose construction do not exhibit those forbidden frequencies. They seem, hence, well suited for an exact and reliable computation of guided modes in photonic crystal wave-guides.

The temperature dependence of the Casimir-Polder interaction addresses fundamental issues for understanding vacuum and thermal fluctuations. It is highly sensitive to surface waves, which, in the near field, govern the thermal emission of a hot surface. Here we use optical reflection spectroscopy to monitor the atom-surface interaction potential between a Cs*(7D3/2) atom and a hot sapphire surface at distances of ~100 nm. In our experiments, that explore a large range of temperatures (500-1,000 K), the surface is at thermal equilibrium with the vacuum. The observed increase of the interaction with temperature, by up to 50%, relies on the coupling between atomic virtual transitions in the infrared range and thermally excited surface-polariton modes. We extrapolate our findings to a broad distance range, from the isolated atom to the short distances relevant to physical chemistry. Our work also opens the prospect of controlling atom-surface interactions by engineering thermal fields.

In this paper, experimental evidences about the resonance phenomena in a negative 2D photonic crystal are shown. Localized plasmon-like modes and guided mode resonances are detected in the reflectivity spectrum of a photonic crystal slab irradiated with out-of-plane incident radiation. The strong confinement of the radiation, in addition to the field enhancement, make photonic crystals a very appealing alternative to plasmonic substrates, avoiding the limits of absorption losses in metals. © The Authors. All rights reserved.

This work is devoted to the analysis of propagating and surface acoustic waves in granular phononic crystals in thelinear regime. First, the propagation and localization of transversal-rotational waves in a two-dimensional granularchain of equal masses are analyzed. By considering the semi-infinite chain with a boundary condition applied at itsbeginning, the analytical study demonstrates the existence of localized modes, each mode composed of two evanescentmodes. Secondly, the phononic properties of a two-dimensional discrete phononic crystal, made of circular cross-section, infinitely long contacting elastic cylinders arranged on a simple cubic lattice, are described analytically. The theoretical analysis provides a clear physical explanation for the existence of a zero-group velocity point of the lowest-energy acoustic mode in particular directions of the phononic crystal and demonstrates the birefraction phenomenon. Finally, the existence of surfaces elastic waves at mechanically free surface of granular phononic crystals is presented. Depending on the degrees of freedom of the particles, different types of surface waves exist in the structure. First, Rayleigh type surface waves aredemonstrated in a granular phononic crystal with particles possessing two translational and one rotational degrees offreedom; and secondly, shear-horizontal surface waves are studied in a granular phononic crystal with particlespossessing two rotational and one translational degrees of freedom. A comparison with surface waves predicted by theCosserat theories is made in order to establish the limitations of the Cosserat theories., Ce travail de thèse porte sur l’étude de la propagation d’ondes de volume et d’ondes de surface dans des cristauxphononiques granulaires en régime linéaire. Différents aspects sont développés dans ce manuscrit. L’effet de la prise encompte des degrés de liberté en rotation des particules sur la structure de bande de différents cristaux phononiquesgranulaires est étudié. En effet, l’introduction de ces degrés de liberté additionnels rend possible l’existence de modes derotation qui interagissent fortement avec les modes transverses. Ce travail s’intéresse aussi à l’existence d’ondeslocalisées et d’ondes de surface dans des cristaux phononiques granulaires et en particulier à la comparaison des théoriesdéveloppées avec les prédictions de la théorie de Cosserat. Dans un premier temps, l’étude d’une chaîne phononique granulaire monoatomique est présentée. En considérant lachaîne semi-infinie avec une condition aux limites appliquée à son extrémité, le modèle analytique démontre l’existence demodes localisés, chaque mode étant composé de deux modes évanescents. Ensuite, une description théorique des modes se propageant dans un cristal phononique granulaire en deux dimensions est présentée. Les particules possèdent trois degrés de liberté, deux en translation et un en rotation. L’analyse des interactions entre ondes de translation et ondes de rotation permet de mettre en évidence une grande richesse de structure de bandes ainsi que des phénomènes particuliers (bandes interdites complètes, cône de Dirac, modes non-monotones, phénomène de double réfraction). Dans un dernier temps, une analyse de l’existence d’ondes de Rayleigh et de cisaillement horizontal dans un cristal phononique granulaire en trois dimensions est effectuée. Les limites de la théorie de Cosserat dans la description d’ondes acoustiques de surface dans les milieux micro- et nano-inhomogènes sont établies.

We consider a magnetic impurity deposited on the surface of a strong topological insulator and interacting with the surface modes by a Kondo exchange interaction. Taking into account the warping of the Fermi line of the surface modes, we derive a mapping to an effective one dimensional model and show that the impurity is fully screened by the surface electrons except when the Fermi level lies exactly at the Dirac point. Using an Abrikosov fermion mean-field theory, we calculate the shape of the electronic density Friedel oscillation resulting from the presence of the Kondo screening cloud. We analyze quantitatively the observability of a six-fold symmetry in the Friedel oscillations for two prototype compounds: Bi$_2$Se$_3$ and Bi$_2$Te$_3$., 22 pages, 6 figures

Electromagnetic periodic structures are of great interest. These structures act as frequency filters and allow the manufacturing of meta-materials which appear to be composite and artificial. They exhibit electromagnetic properties that are unusual to natural materials such as band gaps. This allows new devices to guide, focus or stop the propagation. This is for example useful to avoid coupling between various radiating elements via the characterization of the surface waves which propagate at the interface between air and the periodic structure. This thesis provides a description of the finite element method dedicated to the characterization of periodic structures. Numerical modelling results in eigenvalue problems of large sizes. It involves solving linear systems compounds of sparse matrices. A method is therefore discussed for solving this type of problem, optimizing and combining different algorithms. Before discussing the different aspects of the developed method, we establish an exhaustive list of all the existing methods by stating their advantages and drawbacks. We note that the finite element method can handle a wide range of periodic structures in three dimensions without limitation on their shape. We present different formulations of this method. Then the algorithmic aspects of the method are detailed. We show that an analysis of the resolution settings can impact the physical interpretations of the results. Finally we show the performance of our tool on classical validation results from the bibliography and we discuss the characterization of surface waves. Therefore, the study of a patch antenna array included in metal cavities is conducted. To conclude we can say that the studies conducted in this thesis have resulted in the production of a code used in an environment calculation initially present at ONERA.; En électromagnétisme les structures périodiques suscitent un grand intérêt. Ces structures agissent ainsi comme des filtres fréquentiels et permettent la fabrication de méta-matériaux, composites et artificiels. Elles présentent des propriétés électromagnétiques inédites pour les matériaux naturels telles que des bandes interdites. On a ainsi pu fabriquer de nouveaux dispositifs permettant de guider, de focaliser ou de stopper la propagation. C'est par exemple utile pour éviter le couplage entre différents éléments rayonnants notamment via la caractérisation des ondes de surface qui se propagent à l'interface entre l'air et la structure périodique. Ce travail de thèse s'inscrit dans ce contexte et propose une description de la méthode des éléments finis dédiée à la caractérisation des structures périodiques. La modélisation numérique aboutit à des problèmes de valeurs propres de grandes tailles. Elle implique la résolution de systèmes linéaires composés de matrices creuses. Une méthode est abordée pour résoudre ce type de problème, en optimisant et combinant différents algorithmes. Avant d'aborder les différents aspects de la méthode développée, nous établissons une liste exhaustive de l'ensemble des méthodes qui existent en énonçant leurs avantages et leurs inconvénients. Nous constatons notamment que la méthode des éléments finis permet de traiter un large éventail de structures périodiques en trois dimensions sans limitation sur leur forme géométrique. Nous présentons alors les différentes formulations de cette méthode. Ensuite les aspects algorithmiques de la méthode sont détaillés. Nous montrons notamment qu'une analyse des paramètres de résolution permet de préciser les interprétations physiques des résultats obtenus. Finalement nous présentons les performances de notre outil sur des cas d'applications issus de la littérature et nous abordons la caractérisation des ondes de surface. Pour cela, l'étude d'un réseau d'antennes patchs insérées dans des cavités métalliques est conduite. Notons pour conclure que les études conduites au cours de cette thèse ont abouti à la production d'un code utilisable dans un environnement de calcul initialement présent à l'ONERA.

Electromagnetic periodic structures are of great interest. These structures act as frequency filters and allow the manufacturing of meta-materials which appear to be composite and artificial. They exhibit electromagnetic properties that are unusual to natural materials such as band gaps. This allows new devices to guide, focus or stop the propagation. This is for example useful to avoid coupling between various radiating elements via the characterization of the surface waves which propagate at the interface between air and the periodic structure. This thesis provides a description of the finite element method dedicated to the characterization of periodic structures. Numerical modelling results in eigenvalue problems of large sizes. It involves solving linear systems compounds of sparse matrices. A method is therefore discussed for solving this type of problem, optimizing and combining different algorithms. Before discussing the different aspects of the developed method, we establish an exhaustive list of all the existing methods by stating their advantages and drawbacks. We note that the finite element method can handle a wide range of periodic structures in three dimensions without limitation on their shape. We present different formulations of this method. Then the algorithmic aspects of the method are detailed. We show that an analysis of the resolution settings can impact the physical interpretations of the results. Finally we show the performance of our tool on classical validation results from the bibliography and we discuss the characterization of surface waves. Therefore, the study of a patch antenna array included in metal cavities is conducted. To conclude we can say that the studies conducted in this thesis have resulted in the production of a code used in an environment calculation initially present at ONERA.; En électromagnétisme les structures périodiques suscitent un grand intérêt. Ces structures agissent ainsi comme des filtres fréquentiels et permettent la fabrication de méta-matériaux, composites et artificiels. Elles présentent des propriétés électromagnétiques inédites pour les matériaux naturels telles que des bandes interdites. On a ainsi pu fabriquer de nouveaux dispositifs permettant de guider, de focaliser ou de stopper la propagation. C'est par exemple utile pour éviter le couplage entre différents éléments rayonnants notamment via la caractérisation des ondes de surface qui se propagent à l'interface entre l'air et la structure périodique. Ce travail de thèse s'inscrit dans ce contexte et propose une description de la méthode des éléments finis dédiée à la caractérisation des structures périodiques. La modélisation numérique aboutit à des problèmes de valeurs propres de grandes tailles. Elle implique la résolution de systèmes linéaires composés de matrices creuses. Une méthode est abordée pour résoudre ce type de problème, en optimisant et combinant différents algorithmes. Avant d'aborder les différents aspects de la méthode développée, nous établissons une liste exhaustive de l'ensemble des méthodes qui existent en énonçant leurs avantages et leurs inconvénients. Nous constatons notamment que la méthode des éléments finis permet de traiter un large éventail de structures périodiques en trois dimensions sans limitation sur leur forme géométrique. Nous présentons alors les différentes formulations de cette méthode. Ensuite les aspects algorithmiques de la méthode sont détaillés. Nous montrons notamment qu'une analyse des paramètres de résolution permet de préciser les interprétations physiques des résultats obtenus. Finalement nous présentons les performances de notre outil sur des cas d'applications issus de la littérature et nous abordons la caractérisation des ondes de surface. Pour cela, l'étude d'un réseau d'antennes patchs insérées dans des cavités métalliques est conduite. Notons pour conclure que les études conduites au cours de cette thèse ont abouti à la production d'un code utilisable dans un environnement de calcul initialement présent à l'ONERA.

This paper investigates the near field focusing behavior corresponding to the hyperbolic dispersion regime at the second band of the square lattice photonic crystal (PC). Numerical studies reveal the influence of the corner part negative refraction in the observed focusing effect, though the major part of the ref179{190raction is divergent at this hyperbolic regime. It is further observed that the investigated dispersion shows the surface mode behavior when the effective index of the PC slab is higher than the air medium. This aspect may be implemented for the excitation and transfer of near fields for an evanescent wave microscopy.

In this paper we have demonstrated the existence of surface intrinsic localized modes in one-dimensional classical spin systems. These modes have frequencies above the top of the magnon band and are more localized than the corresponding modes that were found in the lattice dynamics. By numerical methods we have studied the forward evolution in time. These entities are stable in time for many time steps. Also, we consider the interaction of these surface excitations with an external dipolar field. We have first considered the case in which the external dipole is parallel to the spins of the bulk. According to the distance of the impurity from the surface we find that at a particular distance a new surface mode appears, that we have called a mixed mode because it is formed by a localized state at the surface plus a plane wave. At large distances the dipole traps the surface mode, while at small distances the external impurity potential is so strong that all the spins are forced to be aligned in the $z$ direction. For the case in which the external magnetic dipole is antiparallel to the bulk spins there are no mixed modes and the external impurity is so strong that the surface modes are trapped at large distances, and the bulk modes are trapped at very short distances.

7 pages, 5 figures., In this paper, we study how extraordinary transmission through an array of holes in a metallic film appears as a function of the number of holes and their distribution. We have used a theoretical formalism able to analyze the optical properties of finite collections of apertures placed at arbitrary positions in a metallic film. First, we describe how the total transmission in a hexagonal two-dimensional hole array evolves as the number of holes in the array is increased. Second, we study the extraordinary transmission appearing in a single one-dimensional chain of holes. We find that the transmission through this structure is very sensitive to the incident polarization. Third, we show that a single hole flanked symmetrically by two finite chains of dimples can also present extraordinary transmission properties., This work was supported in part by the Spanish MCyT under Grant BES-2003-0374, Contract MAT2002-01534, and Contract MAT2002-00139, and in part by the European Commission (EC) under Project FP6-2002-IST-1-507879 and Project FP6-NMP4-CT-2003-505699.

The existence of surface waves on materials like metals, doped semiconductors, polar materials or photonic crystals modifies their radiative properties.The 1st part of this thesis deals with the coherent and amplified thermal emission by surface plasmon-polaritons. We have designed and fabricated a highly directional tungsten thermal source in the near infrared. We have also studied the radiative cooling of doped silicon thanks to the amplified thermal emission by surface plasmons. We have compared the efficiencies of those coherent sources with the one of an anti-reflective system : the Salisbury screen.In the 2nd part, we study the impact of the near-field radiative transfer on thermophotovoltaic (TPV) energy conversion. The resonant excitation of surface waves on the thermal source illuminating the TPV cell generates an amplified and quasi-monochromatic radiative transfer. We propose a quantitative model of the calculation of the photogeneration current and the efficiency. We show a significant enhancement of both the efficiency and the output electric power of a near-field TPV converter.The 3rd part is dedicated to the radiative properties of photonic crystals induced by surface waves. Two phenomena known in plasmonics have been obtained : the resonant transmission through an opaque film and the coherent thermal emission. A key advantage of photonic crystals is that the resonant frequency can be modified by changing the lattice parameters.; La présence d'ondes de surface sur certains matériaux (métaux, semiconducteurs dopés, cristaux polaires, cristaux photoniques) modifie leurs propriétés radiatives.La 1ère partie de cette thèse est consacrée au phénomène d'émission thermique cohérente et amplifiée par plasmon-polaritons de surface. Nous avons tout d'abord conçu et réalisé une source thermique de tungstène avec une directivité exceptionnelle dans le proche infrarouge. Nous avons ensuite étudié le refroidissement radiatif du silicium dopé grâce à l'amplification d'émission thermique par plasmons de surface. Nous avons comparé les performances de ces sources cohérentes avec celles d'un système anti-réfléchissant : l'écran de Salisbury.Dans la 2ème partie, nous étudions l'impact du transfert radiatif en champ proche sur la conversion thermophotovoltaïque (TPV). L'excitation d'ondes de surface sur la source éclairant la cellule TPV engendre un transfert radiatif amplifié et quasi-monochromatique. Nous présentons un modèle quantitatif permettant de calculer le photocourant et le rendement. Nous montrons que l'on peut obtenir une augmentation significative de la puissance électrique extraite et du rendement d'un dispositif TPV éclairé en champ proche.La 3ème partie porte sur les propriétés radiatives des cristaux photoniques induites par ondes de surface. Deux phénomènes connus en plasmonique ont pu être obtenus : la transmission résonante à travers un film opaque et l'émission thermique cohérente. Un avantage des cristaux photoniques est la possibilité de modifier la fréquence d'excitation des ondes de surface en faisant varier les paramètres du cristal.

The existence of surface waves on materials like metals, doped semiconductors, polar materials or photonic crystals modifies their radiative properties.The 1st part of this thesis deals with the coherent and amplified thermal emission by surface plasmon-polaritons. We have designed and fabricated a highly directional tungsten thermal source in the near infrared. We have also studied the radiative cooling of doped silicon thanks to the amplified thermal emission by surface plasmons. We have compared the efficiencies of those coherent sources with the one of an anti-reflective system : the Salisbury screen.In the 2nd part, we study the impact of the near-field radiative transfer on thermophotovoltaic (TPV) energy conversion. The resonant excitation of surface waves on the thermal source illuminating the TPV cell generates an amplified and quasi-monochromatic radiative transfer. We propose a quantitative model of the calculation of the photogeneration current and the efficiency. We show a significant enhancement of both the efficiency and the output electric power of a near-field TPV converter.The 3rd part is dedicated to the radiative properties of photonic crystals induced by surface waves. Two phenomena known in plasmonics have been obtained : the resonant transmission through an opaque film and the coherent thermal emission. A key advantage of photonic crystals is that the resonant frequency can be modified by changing the lattice parameters., La présence d'ondes de surface sur certains matériaux (métaux, semiconducteurs dopés, cristaux polaires, cristaux photoniques) modifie leurs propriétés radiatives.La 1ère partie de cette thèse est consacrée au phénomène d'émission thermique cohérente et amplifiée par plasmon-polaritons de surface. Nous avons tout d'abord conçu et réalisé une source thermique de tungstène avec une directivité exceptionnelle dans le proche infrarouge. Nous avons ensuite étudié le refroidissement radiatif du silicium dopé grâce à l'amplification d'émission thermique par plasmons de surface. Nous avons comparé les performances de ces sources cohérentes avec celles d'un système anti-réfléchissant : l'écran de Salisbury.Dans la 2ème partie, nous étudions l'impact du transfert radiatif en champ proche sur la conversion thermophotovoltaïque (TPV). L'excitation d'ondes de surface sur la source éclairant la cellule TPV engendre un transfert radiatif amplifié et quasi-monochromatique. Nous présentons un modèle quantitatif permettant de calculer le photocourant et le rendement. Nous montrons que l'on peut obtenir une augmentation significative de la puissance électrique extraite et du rendement d'un dispositif TPV éclairé en champ proche.La 3ème partie porte sur les propriétés radiatives des cristaux photoniques induites par ondes de surface. Deux phénomènes connus en plasmonique ont pu être obtenus : la transmission résonante à travers un film opaque et l'émission thermique cohérente. Un avantage des cristaux photoniques est la possibilité de modifier la fréquence d'excitation des ondes de surface en faisant varier les paramètres du cristal.

We report beaming and enhanced transmission of electromagnetic waves by use of surface corrugated photonic crystals. The modes of a finite-size photonic crystal composed of dielectric rods in free space have been analyzed by the plane-wave expansion method. We show the existence of surface propagating modes when the surface of the finite-size photonic crystal is corrugated. We theoretically and experimentally demonstrate that the transmission through photonic crystal waveguides can be substantially increased by the existence of surface propagating modes at the input surface. In addition, the power emitted from the photonic crystal waveguide is confined to a narrow angular region when an appropriate surface corrugation is added to the output surface of the photonic crystal. © 2005 Optical Society of America.

In this paper we will review recents results relative to localized modes induced by anharmonicity in one-dimensional lattices. We will show that localized modes exists in monoatomic chains with and without a local inhomogeneity in the anharmonic force field. We will compare the discrete and the quasi-continuum intrinsic even and odd localized solutions. This analysis is carried out by taking into account harmonic and quartic anharmonic interactions. We will also present results for the diatomic chains showing the presence of surface modes and gap modes related to the maximum of the acoustic band. In this analysis will be also studied the effect of the cubic anharmonicity. One of the major effects of the cubic anharmonicity is to produce gap modes that split off from the bottom of the optical branch.

A theoretical investigation has been made of the linewidth of the Rayleigh mode on the Al(111) surface due to cubic anharmonic interactions between atoms. The normal-mode frequencies and eigenvectors for the harmonic crystal were calculated by using a model containing central interactions extending up to tenth-nearest neighbors and three-body interactions extending up to second-nearest neighbors. This model reproduces with great accuracy the experimental bulk-phonon frequencies as well as the surface-phonon frequencies. The linewidths were evaluated along the \ensuremath{\Sigma}\ifmmode\bar\else\textasciimacron\fi{} direction as a function of the lateral momentum transfer and at the M\ifmmode\bar\else\textasciimacron\fi{} point as a function of the temperature. The results compare favorably with recent experimental data.

We report measurements on a new collective spin-wave mode trapped by the textural boundary layers of 3 He-A within a stack of thin Mylar plates. The surface mode was seen as a new peak in the cw NMR spectrum measured at H0=284 Oe. Rotation of the sample, with Ω orthogonal to the gaps, increased the spectral weight of the surface mode, indicating an increase in the textural boundary layers caused by a counterflow-induced transition. This phenomenon was used to study vortex creation and persistent currents.

Birim hücresinde farklı boyutlu elemanlara sahip yapılar, yüksek simetrili olanlara göre daha büyük bant genişliklerine, iletim spektrumunda daha zengin karakteristiklere, düşük geri yansıma kayıplarına sahip oldukları için son zamanlarda fotonikte yeni nesil aygıt tasarımlarında yaygın şekilde kullanılmaktadır. Bu tez çalışmasında dönme simetrisi azaltılmış periyodik yapılarda asimetrik iletim özelliği, yüzey modları ve yavaş ışık karakteristiği incelenmiştir. Ayrıca aperiyodik olan kuazi kristallerin yüksek olan dönel simetrisi kırılarak kavite yapısı ve yüzey dalga kılavuzları tasarlanmıştır. Optik sinyali bir yönde iletirken ters yönde yansıtarak yapının diğer tarafına ulaşmasını engelleyen optik diyotlar gelişmiş fotonik uygulamalarında kullanılmaya başlanmıştır. Tezin ilk bölümünde, telekom dalgaboyunda geniş bantlı asimetrik iletim özelliğinin yanında ışığı farklı kırınım mertebelerine ayıran fotonik kristal yapı tasarlanmıştır. Silikon malzemeden oluşan farklı yarıçaplı dielektrik silindirler kullanılarak hetero yapılı tasarlanan kırınım ızgarası ışığın geliş açısına oldukça toleranslıdır. Tasarım gelen ışığı +x yönünde %73 oranında iletebilirken, zıt yön olan –x yönünde ise ışığı belli frekanslarda %99'lara kadar yansıtabilmektedir. Ayrıca fotonik kristal ızgara yapısı ileri yönde gelen dalgayı başarılı şekilde kırınım mertebelerine bölmektedir. Farklı frekanslar yapı tarafından farklı kırınım derecelerine ayrılmaktadır. Gösterdiği bu özellikler sayesinde tasarlanan kristal yapı spektrometre alanında kullanım için uygun bir adaydır. Tezin üçüncü bölümünde ise düşük simetrili periyodik yapılarda frekans seçici ve yavaşlatılmış yüzey Bloch dalgaların yönlü iletiminin kontrolü çalışılmıştır. Bunun için kare örgülü periyodik yapıya ikincil saçıcı elemanlar eklenmiş ve sadece yüzeyde yer alan ikincil silindirlerin konumları modifiye edilerek yüzey modun frekansının yanı sıra, ilerleme hızı ve ilerleme yönü de kolayca kontrol edilmiştir. Dizilim açısının düşük değerlerinde yüzeyin grup indisi 237'ye kadar yükselmiştir. Yüzeye tutunan dalgalar indis güdümlü olduğu için dizilimsel değişiklik elektik alan dağılımının farklılaşmasına sebep olmuştur. Böylece yapının etkin kırılma indisi değişerek yüzey mod frekansın modifiye edilmesini sağlamıştır. Bu özelliklerinin yanı sıra bant diyagramında ortaya çıkan yüzey modların negatif eğime sahip olmalarını ters yönlü iletimin mümkün olduğunu göstermiştir. Düşük dizilim açılarında ışık her iki yönde birden ilerlerken, dizilim açısı arttıkça geri yönlü iletim baskın hale gelmektedir. Yüzeyde kolayca modifiye edilebilen yavaş ışık sayesinde tasarım, güneş pillerinde, sensör uygulamalarında ve ışın ayırıcı dalga kılavuzu olarak interferometrelerde kullanılabilir. Tezin son bölümünde ise sekizgen simetrili kuazi kristallerin yüksek olan dönel simetrisi düşürülerek kavite etkisinde ve yüzey modlarda yüksek simetrili olan standart yapıya göre üstün özellikler sergilemesi sağlanmıştır. Kuazi kristalde kavite modlarının frekansı, mod alanları ve kalite faktörleri kontrol edilmiştir. Yüzeyde meydana getirilen modifikasyon bu dizilimlerde de yüzey dalgaların elde edilmesini sağlamıştır. Yüzeyde yer alan silindirlerin büyüklük ve konum değişimi sayesinde frekans ayarlaması mümkün hale gelmiştir., Recently in new generation photonic devices, the designs having elements with different sizes in the unit cell are widely used in photonics, since they have larger bandwidths, richer characteristics in the transmission spectrum, lower back reflection losses than those with high symmetry. In this thesis, asymmetric transmission properties, surface modes, and slow light characteristics are examined in the periodic structures with reduced rotational symmetry. In addition, cavity structure and surface waveguides are designed by breaking the high rotational symmetry of quasicrystals. The optical diodes are used in advanced photonics applications that prevent the optical signal to reach the other side of the structure. In the first part of the thesis, in addition to the broadband feature of the asymmetric transmission at the telecom wavelength, the photonic crystal structure has been designed to separate the light into different diffraction orders. The diffraction grating, which is designed in a heterogeneous manner using dielectric cylinders with different radii of silicon material, is very tolerant of the incident angle of the light wave. The design can transmit the light in the direction of +x by 73%, while the photonic crystal diffraction grating can reflect light at certain frequencies up to 99% in the opposite direction. In addition, the grating structure successfully divides the forward wave into the diffraction orders. The crystal structure designed with these features is a suitable candidate for use in the field of the spectrometer. In the third part of the thesis, control of the directional transmission of frequency selective and decelerated surface Bloch waves in low symmetric periodic structures is studied. For this purpose, additional elements have been added to the periodic structure and only the positions of the cylinders on the surface have been modified, as well as the frequency of the surface mode, the group velocity and the direction of propagation have been easily controlled. At the low values of the orientation angle, the group index of the surface increased to the value of 237. Since the waves that are attached to the surface are index guided, the position change of the rods causes the electric field distribution to vary. The changing effective refractive index of the structure allows the modulation of the surface frequency. Also, the negative slope of the surface modes appearing in the band diagram shows that backward transmission is possible on the structure surface. For the low orientation angles, the light travels in both directions, while the backward propagation becomes more dominant as the angle of orientation increases. Owing to the slow light property of the surface modes which can be easily modified on the surface, the design can be used in solar cells, sensor applications, and interferometers as a beam splitter waveguide. In the last part of the thesis, the high rotational symmetry of the octagonal quasicrystals is reduced to enhance the performance of the design in terms of cavity effect and surface modes. In quasicrystal, frequency, mode areas, and quality factors of the cavity modes are easily controlled. The surface-induced modification provides surface waves in this arrangement. Thanks to the size and position change of the cylinders located on the surface, frequency adjustment has become possible.

We determine the presence of plasmonic surface modes under TE polarization in an optical fiber made of a dispersive left handed material. These modes keep clearly localized at a constant frequency within the numerical error, despite strong geometrical changes in the physical system. To prove this fact we analyze systems having random roughness on their surfaces and consider other geometry variations. The electromagnetic field distribution is determined in the region where plasmonic and non plasmonic modes exist.