Mid-Infrared thermal emission sources based on graphene were investigated both experimentally and simulated using the finite element method modelling software package COMSOL. Devices were fabricated by transferring graphene onto various substrates. The thermal emission of few-layer and single graphene on SiO2/Si, under a pulsed square wave drive current, was characterised using spatially resolved thermal emission measurements. It was determined that the devices with single-layer graphene maintained characteristic properties of graphene, while few-layer graphene displayed properties typical of a semi-metal. The effect of thermal management on the emission was investigated by comparing simulations to the emission from these devices and a hexagonal boron nitride encapsulated few-layer graphene device. Limiting the vertical heat dissipation was shown to improve device modulation speed. The emission from the graphene devices was determined to be grey-body in nature. Metamaterial structures, including ring resonators and split ring resonators, were integrated with the encapsulated devices in order to narrow the emission spectra. The emission and reflectance of the devices was characterised using Fourier transform infrared spectroscopy. A tuneable electromagnetically induced transparency like spectral response was observed for devices with metamaterial structures. The resonance peaks were shifted by altering the unit cell parameters. Finally, gallium nitride nano-rod arrays were investigated for the potential to incorporate both spectral control and thermal management into the underlying substrate, in addition to the possibility of the optical generation of graphene plasmons. It was determined that the conventional wet transfer technique was inadequate to transfer the graphene onto the nano-rods. Therefore, a modified transfer technique was utilised, with a significant improvement in the graphene coverage observed. Optical characterisation of the nano-rods using Fourier transform infrared reflectance spectroscopy indicated the excitation of localised surface phonon polaritons, while no evidence was observed in the graphene reflectance spectra of the generation of graphene plasmons.

Les sources infrarouges sont indispensables à la détection locale de gaz dans de nombreux domaines, que ce soit pour l'environnement (détection de polluants et gaz à effets de serre) ou la défense (détection de menaces biologiques et chimiques). Elles sont également nécessaires en tant que mires de calibration pour le développement de caméras multispectrales infrarouges. Pour toutes ces applications, il est nécessaire de disposer de sources performantes, capables d'émettre un rayonnement spécifique dans une direction donnée. L'objectif de cette thèse est de concevoir des sources thermiques infrarouges compactes et à coût modéré, à spectre accordable et à pertes réduites, pouvant être juxtaposées dans un même dispositif. Pour cela, ces travaux s'organisent autour de deux axes. Le premier concerne l'étude de nouveaux matériaux nanostructurés résonants, appelés métamatériaux ou métasurfaces selon les directions de la structuration, permettant de contrôler l'émissivité spectrale et spatiale afin de maîtriser la réponse spectrale en tout point. Cette étude repose à la fois sur des simulations numériques et sur des mesures expérimentales et démontre le potentiel de ces résonateurs pour la conception de sources thermiques accordables. Cependant, ces matériaux étant composés de métal, ils présentent des pertes par absorption dans l'infrarouge qui limitent leurs performances. Le deuxième axe de recherche est alors de gérer les pertes liées à l'utilisation de métaux grâce à une ingénierie des champs dans des métamatériaux, menant à des émissions spectralement très fines. Les résultats obtenus sur ce contrôle des pertes ouvrent de nombreuses perspectives pour tout le domaine des métamatériaux. / Infrared sources are essential for local gas detection for civil applications (detection of pollutant and greenhouse gas) or military applications (detection of chemical and biological threats). They are also used as calibration targets for the development of multispectral infrared cameras. For these applications, the sources must be efficient and able to emit a specific light in a given direction. The aim of this thesis is to develop infrared thermal emitters with the following features: low cost with a compact volume, with a tunable spectral response and low losses, able to be juxtaposed on the same device. This work begins with the study of new resonant nanostructured materials, called metamaterials or metasurfaces according to the direction of the structuration, that spectrally and spatially control the emitted light up to the wavelength scale. This study relies on numerical simulations and experimental measurements and demonstrates the potential of these resonators as tunable thermal sources. However, due to the use of metals in these materials, their performance is limited by metal losses. The second study of this work is then to deal with these losses thanks to a field engineering in metamaterials, leading to very narrow spectral responses. The results on this loss control open up promising breakthroughs in the plasmonic and metamaterials field

A negative index material (NIM), which possesses simultaneously negative permittivity and permeability, is an emerging material that has caught many researchers attention after it was first demonstrated in 2001. It has been shown that electromagnetic waves propagating in NIMs have some remarkable properties such as negative phase velocities and negative refraction and hold enormous promise for applications in imaging and optical communications. This dissertation is centered on investigating the unique aspects of the radiative properties of NIMs. Photon tunneling, which relies on evanescent waves to transfer radiative energy, has important applications in thin-film structures, microscale thermophotovoltaic devices, and scanning thermal microscopes. With multilayer thin-film structures, photon tunneling is shown to be greatly enhanced using NIM layers. The enhancement is attributed to the excitation of surface or bulk polaritons, and depends on the thicknesses of the NIM layers according to the phase matching condition. A new coherent thermal emission source is proposed by pairing a negative permittivity (but positive permeability) layer with a negative permeability (but positive permittivity) layer. The merits of such a coherent thermal emission source are that coherent thermal emission occurs for both s- and p-polarizations, without use of grating structures. Zero power reflectance from an NIM for both polarizations indicates the existence of the Brewster angles for both polarizations under certain conditions. The criteria for the Brewster angle are determined analytically and presented in a regime map. The findings on the unique radiative properties of NIMs may help develop advanced energy conversion devices. Motivated by the recent advancement in scanning probe microscopy, the last part of this dissertation focuses on prediction of the radiation heat transfer between two closely spaced semi-infinite media. The objective is to investigate the dopant concentration of silicon on the near-field radiation heat transfer. It is found that the radiative energy flux can be significantly augmented by using heavily doped silicon for the two media separated at nanometric distances. Large enhancement of radiation heat transfer at the nanoscale may have an impact on the development of near-field thermal probing and nanomanufacturing techniques.

In this dissertation, I present my work on the behaviour of different features of radio-loud active galaxies to investigate how energy is transferred from their jets to the environment. To this end, I have studied the knots in the jet in Centaurus A, the radio and X-ray emission from the lobes of the FRII radio galaxies 3C 353 and Pictor A, and the gas properties of a sample of galaxy groups some of which host radio-loud AGN. Using new and archival multi-frequency radio and X-ray data for Centaurus A obtained over almost 20 years with the Very Large Array and with Chandra, I have measured the X-ray and radio spectral indices, flux density variations, polarisation variations and proper motions of the jet knots. I used these measurements to constrain the likely knot formation mechanisms and particle acceleration processes within this jet and compared my results with the variations detected in the properties of the knots in M87. I found that none of the knots are a result of impulsive particle acceleration and that those knots that are detected in both X-ray and radio are likely due to collisions between the jet and an obstacle, while the radio only knots, the majority of which are moving, are likely due to compressions of the fluid flow. Using six frequencies of new and archival radio data and new XMM-Newton observations of 3C 353, I show that inverse-Compton emission is detected in the lobes of this source. By combining this X-ray emission with the radio synchrotron emission, I have constrained the electron population and the magnetic field energy density in the lobes of this radio galaxy. I have argued that the variations in the X-ray/radio ratio in the brighter lobe requires a changing magnetic field strength. I have extended this work using a statistical analysis of the X-ray and radio emission to show that the observed small-scale variation in surface brightness cannot be reproduced by simple combinations of the electron energy distribution and the magnetic field strength. I therefore suggest that the changes in surface brightness that give rise to the filamentary structures seen in the lobes are probably due to strong spatial variations of the magnetic field strength. Finally, I present a study of galaxy groups observed with XMM-Newton in which I measure temperature and surface brightness profiles to examine whether radio-source heating makes radioloud groups hotter and more luminous than radio-quiet groups. I compare my measurements with previous luminosity-temperature relationships and conclude that there is a significant difference in the gas properties of radio-loud and radio-quiet groups.

abstract: Interpreting the petrogenesis of materials exposed on the surface of planets and asteroids is fundamental to understanding the origins and evolution of the inner Solar System. Temperature, pressure, fO2, and bulk composition directly influence the petrogenetic history of planetary surfaces and constraining these variables with remote sensing techniques is challenging. The integration of remote sensing data with analytical investigations of natural samples, lab-based spectroscopy, and thermodynamic modelling improves our ability to interpret the petrogenesis of planetary materials. A suite of naturally heated carbonaceous chondrite material was studied with lab-based spectroscopic techniques, including visible near-infrared and Fourier transform infrared reflectance spectroscopy. Distinct mineralogic, and thus spectroscopic, trends are observed with increasing degree of thermal metamorphism. Characterization of these spectral trends yields a set of mappable parameters that will be applied to remotely sensed data from the OSIRIS-REx science payload. Information about the thermal history of the surface of the asteroid Bennu will aid in the selection of a sampling site, ensuring OSIRIS-REx collects a pristine regolith sample that has not experienced devolatilization of primitive organics or dehydration of phyllosilicates. The evolution of mafic magma results in distinct major element chemical trends. Mineral assemblages present in evolved volcanic rocks are indicators of these processes. Using laboratory spectroscopic analyses of a suite of evolved volcanic rocks from the Snake River Plain, Idaho, I show that these evolutionary trends are reflected in the spectral signatures of ferromagenesian and feldspar minerals. The Athena science package on the Mars Exploration Rover Spirit allows for the in situ investigation of bulk chemistry, texture, and mineralogy on the surface of Mars. Using the bulk composition of the Irvine and Backstay volcanic rocks, thermodynamic modeling was performed to further constrain the formation conditions of Martian volcanics. Irvine and Backstay compositions exhibit dramatic variations in modal mineralogy with changing fO2. Using these results, I show that the observed Mini-TES spectra of Irvine and Backstay can be adequately reproduced, and additional constraints can be placed on their primary fO2. / Dissertation/Thesis / Doctoral Dissertation Geological Sciences 2018

Les connaissances sur l'origine de Radio Halos (RHs), sources radio diffuses de faible brillance de surface observées aux échelles des Mpc dans les amas de galaxies massives, ont progressé vers un consensus général au cours des dernières années. Le scénario généralement accepté pour le mécanisme responsable de ce type d'émission diffuse est la ré-accélération des électrons relativistes par les turbulence générées au cours de la coalescence entre amas. Dans ce cadre, les modèles prévoient une fraction plus importante de RHs dans intervalle z = 0.3-0.4. Cependant, les observations radio des amas de galaxies dans ce régime de redshift sont encore limitées. Le projet MACS-Planck Radio Halo Cluster Project vise à explorer l'origine des RHs, ainsi que leur lien avec l'état dynamique des systèmes hôtes, en explorant une gamme de redshift plus élevée par rapport aux études précédentes. Dans cette thèse, je présente les données publiées du sous-échantillon ATCA du projet et les perspectives pour les travaux futurs. / The knowledge on the origin of Radio Halos (Rhs), Mpc-scale low surface brightness diffuse radio emission observed in massive galaxy clusters, has moved towards a general consensus on the recent years. The generally accepted scenario for the mechanism responsible of this kind of diffuse emission is the re-acceleration of relativistic electrons by the turbulence generated in cluster mergers. On this framework, it is expected from models that a larger fraction of RH occurrence may appear at z=0.3-0.4. However, radio observations of galaxy clusters in this redshift regime are still limited. The MACS-Planck Radio Halo Cluster Project has the aim of exploring the origin and occurrence of RHs, as well as their connection with the dynamical state of the host systems by exploring a higher redshift range than previous studies. In this thesis, I present the published data of the ATCA subsample of the project and prospects for the future work.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第21270号 / 工博第4498号 / 新制||工||1700(附属図書館) / 京都大学大学院工学研究科電子工学専攻 / (主査)教授 野田 進, 教授 藤田 静雄, 教授 川上 養一 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

Reflectarrays are passive quasi-periodic sub-wavelength antenna arrays designed for discrete reflected phase manipulation at each individual antenna element making up the array. By spatially varying the phase response of the antenna array, reflectarrays allow a planar surface to impress a non-planar phasefront upon re-radiation. Such devices have become commonplace at radio frequencies. In this dissertation, they are demonstrated in the infrared for the first time--at frequencies as high as 194 THz. Relevant aspects of computational electromagnetic modeling are explored, to yield design procedures optimized for these high frequencies. Modeling is also utilized to demonstrate the phase response of a generalized metallic patch resonator in terms of its dependence on element dimensions, surrounding materials, angle of incidence, and frequency. The impact of realistic dispersion of the real and imaginary parts of the metallic permittivity on the magnitude and bandwidth of the resonance behavior is thoroughly investigated. Several single-phase reflectarrays are fabricated and measurement techniques are developed for evaluating these surfaces. In all of these cases, there is excellent agreement between the computational model results and the measured device characteristics. With accurate modeling and measurement, it is possible to proceed to explore some specific device architectures appropriate for focusing reflectarrays, including binary-phase and phase-incremental approaches. Image quality aspects of these focusing reflectarrays are considered from geometrical and chromatic-aberration perspectives. The dissertation concludes by briefly considering two additional analogous devices--the transmitarray for tailoring transmissive phase response, and the emitarray for angular control of thermally emitted radiation.

No description available.

The spectral and directional control of radiative properties by utilizing engineered micro/nanostructures has enormous applications in photonics, microelectronics, and energy conversion systems. The present dissertation aims at: (1) design and analysis of micro/nanostructures based on wave interference and magnetic resonance effects to achieve tunable coherent thermal emission or enhanced optical transmission; (2) microfabrication of the designed structures; and (3) development of a high-temperature emissometer to experimental demonstrate coherent thermal emission from fabricated samples at temperatures from 300 K to 800 K. Asymmetric Fabry-Perot resonant cavities were studied as a potential coherent emission source. The reflectance was measured at room temperature using a Fourier-transform infrared spectrometer, and the emittance can be indirectly obtained from Kirchhoff's law. A high-temperature emissometer was built to measure the thermal emission of fabricated samples, and the temperature effect on the emission peaks was discussed. The direct and indirect approaches were unified and a generalized Kirchhoff's law was deduced to calculate thermal emission from layered structures with nonuniform temperatures. Magnetic polaritons were identified as a mechanism for achieving extraordinary optical transmission/absorption, through the comparison between equivalent capacitor-inductor models and the rigorous coupled-wave analysis. With carefully tuned geometric parameters, the resonance frequencies can be tailored for specific applications. A coherent emission source was designed with grating structures by excitation of magnetic polaritons, and is well suitable for thermophotovoltaic applications, thanks to the spectral selectivity and directional insensitivity of magnetic polaritons. Test samples were fabricated, and coherent thermal emission was experimentally observed at room temperatures up to 800 K. The results obtained in this dissertation will facilitate the design and application of micro/nanostructures in energy-harvesting systems.