Monocentric lenses provide compact, broadband, high resolution, wide-field imaging. However, they produce a curved image surface and have found limited use. The use of an appropriately machined fiber bundle to relay the curved image plane onto a flat focal plane array (FPA) has recently emerged as a potential solution. Unfortunately the spatial sampling that is intrinsic to the fiber bundle relay can have a negative effect on image resolution, and vignetting has been identified as another potential shortcoming of this solution. This thesis describes a metamaterial lens yielding a high-performance image relay from a curved surface to a flat focal plane. Using quasi-conformal transformation optics, a Maxwell's fish-eye lens is transformed into a concave-plano shape. A design with a narrower range of constitutive parameters is deemed more likely to be manufacturable. Therefore, the way in which the particular shape of the concave-plano reimager influences the range of needed constitutive parameters is explored. Finally, image quality metrics, such as spot size and light efficiency, are quantified.

This thesis deals with microstrip antennas covered by the metamaterials. First, are described planar antennas, their problems and the emergence of surface waves. Surface waves can cause unwanted coupling among particular parts of the structure and can degrade its parameters. The problem can be solved using an electromagnetic band gap structure (EBG). These periodic structures are able to suppress surface waves in different frequency bands. It is shown how the EBG structure in the function superstate improve directivity and antenna gain. Radiation conventional microstrip antenna with metallo-dielectric EBG superstrate and with the purely dielectric double-layer superstrate is described. The both structures are designed and simulated in CST Microwave Studio program. Further is described the antenna radiation with so-called mushroom structure and metallo-dielectric EBG superstate. The structure is again designed and simulated in CST MWS program. Finally, there are two structures with metallo-dielectric superstate implemented and measured.

Cette thèse a pour but de mettre en avant les récentes avancées dans le domaine des métasurfaces. Ces structures ont été utilisées dans le but d’améliorer les performances des antennes classiques ou de concevoir de nouveaux concepts d’antenne. Les travaux menés s’inscrivent dans le cadre d’une collaboration avec des partenaires industriels qui sont Airbus Safran Lunchers, Airbus Group Innovations et le CNES. La thèse est organisée en deux parties. La première partie est consacrée aux métasurfaces utilisées comme des surfaces partiellement réfléchissantes (SPR) pour concevoir des antennes à cavité Fabry-Perot. Un modèle analytique permettant de prédire le dépointage du faisceau d’antenne par une modulation de la phase sur la SPR a été développé. Ensuite, un nouveau concept de métasurface permettant de réaliser du dépointage de faisceau est proposé. Il consiste à appliquer un gradient de phase en faisant varier l’indice effectif le long du substrat diélectrique de la SPR. La deuxième partie de cette thèse est quant à elle consacrée à la conception d’une métasurface active permettant d’émuler plusieurs fonctions. Dans un premier temps, la métasurface est utilisée comme un réflecteur présentant une reconfigurabilité fréquentielle et angulaire. Ensuite cette métasurface est utilisée comme polariseur reconfigurable où une polarisation linéaire de l'onde incidente est convertie en polarisation circulaire. Enfin, la dernière étude concerne l’utilisation de la métasurface active pour la réalisation d’une antenne à réflecteur cylindro-parabolique et à réflecteur dièdre reconfigurables. / This thesis aims at highlighting recent advances in the field of metasurfaces. These structures have been used to improve the performances of conventional antennas or to design new antenna concepts. The work has been carried in the framework of a collaboration with industrial partners, namely Airbus Safran Launchers, Airbus Group Innovations and CNES. The manuscript is organized into two parts. The first part is devoted to metasurfaces used as partially reflecting surfaces (PRS) to design Fabry-Perot cavity antennas. In this part, an analytical model allowing to predict the beam steering angle by a phase modulation along the PRS is developed. Then, a new concept of metasurface allowing to steer the main antenna beam is proposed. It consists in applying a phase gradient by varying the effective index of the substrate that constitutes the PRS. The second part of this thesis is devoted to the design of an active metasurface that allows emulating different functionalities. First, the metasurface is utilized as a reflector with frequency and steering reconfigurability characteristics. Then, this metasurface is used as a reconfigurable polarizer where linearly polarized incident waves are converted into circularly polarized ones. Finally, the last study concerns the use of the active metasurface for the design of reconfigurablecylindro-parabolic and corner reflector antennas.

No description available.

<p>Advances in additive manufacturing technologies enable the rapid, high-throughput generation of mechanically soft microelectromechanical devices with tailored designs for many applications spanning from optical to biomedical applications. These devices can be softly interfaced with biological tissues and mechanically fragile systems, which enables to open up a whole new range of applications. However, the scalable production of these devices faces a significant challenge due to the complexity of the microfabrication process and the intolerable thermal, chemical, and mechanical conditions of their flexible polymeric substrates. To overcome these limitations, I have developed a set of advanced additive manufacturing technologies enabling (1) mechanics-driven manufacturing of quasi-three-dimensional (quasi-3D) nanoarchitectures with arbitrary substrate materials and structures; (2) repetitive replication of quasi-3D nanoarchitectures for infrared (IR) bandpass filtering; (3) electrochemical reaction-driven delamination of thin-film electronics over wafer-scale; (4) rapid custom printing of soft poroelastic materials for biomedical applications. </p> <p>First, I have developed a new mechanics-driven nanomanufacturing method enabling large-scale production of quasi-3D plasmonic nanoarchitectures that are capable of controlling light at nanoscale length. This method aims to eliminate the need for repetitive uses of conventional nanolithography techniques that are time- and cost-consuming. This approach is innovative and impactful because, unlike any of the conventional manufacturing methods, the entire process requires no chemical, thermal, and mechanical treatments, enabling a large extension of types of receiver substrate to nearly arbitrary materials and structures. Pilot deterministic assembly of quasi-3D plasmonic nanoarrays with imaging sensors yields the most important advances, leading to improvements in a broad range of imaging systems. Comprehensive experimental and computational studies were performed to understand the underlying mechanism of this new manufacturing technique and thereby provide a generalizable technical guideline to the manufacturing society. The constituent quasi-3D nanoarchitectures achieved by this manufacturing technology can broaden considerations further downscaled plasmonic metamaterials suggest directions for future research.</p> <p>Second, I have developed mechanics-driven nanomanufacturing that provides the capability to repetitively replicate quasi-3D plasmonic nanoarchitectures even with the presence of an extremely brittle infrared-transparent spacer, such as SU-8, thereby manipulating IR light (e.g., selectively transmitting a portion of the IR spectrum while rejecting all other wavelengths). Comprehensive experimental and computational studies were performed to understand the underlying nanomanufacturing mechanism of quasi-3D plasmonic nanoarchitectures. The spectral features such as the shape of the transmission spectrum, peak transmission and full width at half maximum (FWHM), etc. were studied to demonstrate the bandpass filtering effect of the assembled quasi-3D plasmonic nanoarchitecture.</p> <p>Third, I have developed an electrochemical reaction-driven transfer printing method enabling a one-step debonding of large-scale thin-film devices. Conventional transfer printing methods have critical limitations associated with an efficient and intact separation process for flexible 3D plasmonic nanoarchitectures or bio-integrated electronics at a large scale. The one-step electrochemical reaction-driven method provides rapid delamination of large-scale quasi-3D plasmonic nanoarchitectures or bio-integrated electronics within a few minutes without any physical contact, enabling transfer onto the target substrate without any defects and damages. This manufacturing technology enables the rapid construction of quasi-3D plasmonic nanoarchitectures and bio-integrated electronics at a large scale, providing a new generation of numerous state-of-art optical and electronic systems.</p> <p>Lastly, I have developed a new printing method enabling the direct ink writing (DIW) of multidimensional functional materials in an arbitrary shape and size to rapidly prototype stretchable biosensors with tailored designs to meet the requirement of adapting the geometric nonlinearity of a specific biological site in the human body. Herein, we report a new class of a poroelastic silicone composite that is exceptionally soft and insensitive to mechanical strain without generating significant hysteresis, which yields a robust integration with living tissues, thereby enabling both a high-fidelity recording of spatiotemporal electrophysiological activity and real-time ultrasound imaging for visual feedback. Comprehensive <i>in vitro</i>, <i>ex vivo</i>, and <i>in vivo</i> studies provide not only to understand the structure-property-performance relationships of the biosensor but also to evaluate infarct features in a murine acute myocardial infarction model. These features show a potential clinical utility in the simultaneous intraoperative recording and imaging on the epicardial surface, which may guide a definitive surgical treatment.</p>

Plasmonic metasurfaces enable functionalities that extend beyond the possibilities of classical optical materials and as a result, have gained significant research interest over the years. This thesis aims towards introducing plasmonic metamaterials and metasurfaces, a two-dimensional subset of metamaterials. The thesis also provides insights into the nonlinear optical responses from subwavelength metallic nanostructures manifesting as extraordinary physical phenomena like the second harmonic generation (SHG). The hydrodynamic Drude model is a theory that characterizes electron conduction in a hydrodynamic way to predict optical responses of metals. The thesis discusses the various contributions to the second-order optical nonlinearities from the terms in the hydrodynamic model: Coulomb, convection, and the Lorentz magnetic force. The significance of these terms, specifically the Lorentz magnetic term, is validated in contrast with existing research. The details of the work carried out to achieve a significant contribution to SHG from the Lorentz magnetic term are provided. A dominant Lorentz magnetic force for SHG was achieved through engineering T-shaped aperture arrays milled into a thin gold film. The dimensions of these structures were tuned for fundamental wavelength resonance. The structures exhibit both magnetic and electric field enhancements at the plasmonic resonance. Furthermore, a revised theoretical model is developed to accurately predict both linear and nonlinear optical responses of metamaterials. The model is based on the hydrodynamic Drude model and nonlinear scattering theory. Results from the finite difference time domain simulations performed on the metasurface are presented. It is observed that the T-shaped structure provides 65% greater nonlinear generation from the Lorentz magnetic term than the sum of the other two hydrodynamic terms. The influence of incident beam polarization on SHG conversion efficiency was also investigated. It was discovered that even though the contributions of hydrodynamic (Coulomb and convection) terms are maximum at 0◦ and 90◦, the metasurface shows maximum SHG intensity at 45◦ which indicates a dominant Lorentz magnetic term. Experimental validation was performed using the fabricated metasurface and a good agreement between the experiment and theoretical calculations was observed. Another aspect of the magnetic Lorentz force contribution, Bethe’s aperture theory was evaluated for a circular aperture at off-normal incident light. It is shown that the Lorentz force dominates the SHG by an order of magnitude at angled incidence where the generation is maximized. The angular dependence was observed to match the magnetic and electric dipole interaction effects as predicted from Bethe’s theory. The revised theory developed in this thesis predicts the linear and nonlinear optical responses of metamaterials including their angular dependency. The analysis and numerical calculations for a circular aperture agree well with past experiments. To conclude, the thesis provides an outlook on future developments in the field of nonlinear plasmonic research with regards to the development of highly efficient nonlinear metasurfaces through optimization of the Lorentz contributions. An insight into the recent developments in nanofabrication capabilities, design methodologies, nano-characterization techniques, modern electromagnetic simulations is discussed as avenues for future research in nanophotonic and nanoplasmonic device design and development. / Graduate

Programmable matter is a material whose properties can be programmed to achieve particular shapes or mechanical properties upon command. This is an essential technique that could one day lead to morphing aircraft and ground vehicles. Metamaterials are the rationally designed artificial materials whose properties are not observed in nature. Their properties are typically controlled by geometry rather than chemical compositions. Combining metamaterials with a programmable function will create a new area in the intelligent material design. The objective of this study is to design and demonstrate a tunable metamaterial and to investigate its thermo-mechanical behavior. An integrated approach to the metamaterial design was used with analytical modeling, numerical simulation, and experimental demonstration. The dynamic thermo-mechanical analysis was used to measure base materials' modulus and thermal expansion coefficient as a function of temperature. CPS, the unit cell of the metamaterial, is composed of circular holes and slits. By decomposing kinematic rotation of the arm and elastic deformation of a bi-material hinge, thermo-mechanical constitutive models of CPS were developed and it was extended to 3D polyhedral structures for securing isotropic properties. Finite element based numerical simulations of CPS and polyhedral models were conducted for comparison with the analytical model. 3D printing of multi-materials was used for sample fabrication followed by tests with uniaxial compressive mechanical tests and thermal tests at 50℃. From the analytical model of the metamaterial, the contour plots were obtained for the effective properties – Poisson's ratio, the effective coefficient of thermal expansion of the metamaterial as a function of geometry and materials. A controllable range of temperature and strain was identified associated with maximized thermal expansion mismatch and contact on the slit surface of CPS, respectively. This work will pave the road toward the design of programmable metamaterials with both mechanically- and thermally- tunable capability and provide unique thermo-mechanical properties with a programmable function.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第18469号 / 工博第3905号 / 新制||工||1599(附属図書館) / 31347 / 京都大学大学院工学研究科機械理工学専攻 / (主査)教授 西脇 眞二, 教授 椹木 哲夫, 教授 松原 厚 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第18470号 / 工博第3906号 / 新制||工||1600(附属図書館) / 31348 / 京都大学大学院工学研究科電子工学専攻 / (主査)教授 北野 正雄, 教授 和田 修己, 准教授 山田 啓文 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第21754号 / 工博第4571号 / 新制||工||1712(附属図書館) / 京都大学大学院工学研究科機械理工学専攻 / (主査)教授 西脇 眞二, 教授 北村 隆行, 教授 小森 雅晴 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM