The interaction of light with small designed particles and structures gives rise to an increasing number of phenomena of potentially dramatic technological importance, such as metamaterials, superlens focusing, and enhanced spectroscopy. Metallic nanostructures with their geometry-dependent optical resonances are a topic of intense current interest due to their ability to manipulate light in ways not possible with conventional optical materials. A particularly fascinating aspect of these systems is the recently realized possibility of creating optical frequency “magnetic plasmon” responses of comparable magnitude to the “electric plasmon” response. Au nanocups at their magnetoinductive resonance have the unique ability to redirect scattered light in a direction dependent on cup orientation, as a true three-dimensional nanoantenna. As optical frequency nanoantennas, reduced-symmetry plasmonic nanoparticles have light-scattering properties that depend strongly on geometry, orientation, and variations in dielectric environment. Here we investigate how these factors influence the spectral and angular dependence of light scattered by Au nanocups. A simple dielectric substrate causes the axial, electric dipole mode of the nanocup to deviate substantially from its characteristic cos square free space scattering profile, while the transverse, magnetic dipole mode remains remarkably insensitive to the presence of the substrate. Nanoscale irregularities of the nanocup rim and the local substrate permittivity have a surprisingly large effect on the spectral- and angle-dependent light-scattering properties of these structures. The different angular scattering and wavelength response from the axial and transverse nanocup modes make the nanocup an interesting particle for the nanoscale manipulation of light in three dimensions. The sensitivity of this system to geometric and environmental factors may present opportunities for active, substrate-mediated control of light scattering.

The interaction of light with small designed particles and structures gives rise to an increasing number of phenomena of potentially dramatic technological importance, such as metamaterials, superlens focusing, and enhanced spectroscopy. Metallic nanostructures with their geometry-dependent optical resonances are a topic of intense current interest due to their ability to manipulate light in ways not possible with conventional optical materials. A particularly fascinating aspect of these systems is the recently realized possibility of creating optical frequency “magnetic plasmon” responses of comparable magnitude to the “electric plasmon” response. Au nanocups at their magnetoinductive resonance have the unique ability to redirect scattered light in a direction dependent on cup orientation, as a true three-dimensional nanoantenna. As optical frequency nanoantennas, reduced-symmetry plasmonic nanoparticles have light-scattering properties that depend strongly on geometry, orientation, and variations in dielectric environment. Here we investigate how these factors influence the spectral and angular dependence of light scattered by Au nanocups. A simple dielectric substrate causes the axial, electric dipole mode of the nanocup to deviate substantially from its characteristic cos square free space scattering profile, while the transverse, magnetic dipole mode remains remarkably insensitive to the presence of the substrate. Nanoscale irregularities of the nanocup rim and the local substrate permittivity have a surprisingly large effect on the spectral- and angle-dependent light-scattering properties of these structures. The different angular scattering and wavelength response from the axial and transverse nanocup modes make the nanocup an interesting particle for the nanoscale manipulation of light in three dimensions. The sensitivity of this system to geometric and environmental factors may present opportunities for active, substrate-mediated control of light scattering.

Orientador: Antonio Accioly / Banca: José Geraldo Pereira / Banca: José Wadih Maluf / Banca: Ilya Lvovich Shapiro / Banca: João Barcelos Neto / Resumo: A gravitação quadrática em (2 + 1)D, ao contrário da gravitação tridimensional de Einstein, é localmente não trivial e possui um potencial extremamente bem comportado. Analisa-se esta teoria neste trabalho. Obtém-se a solução geral das equações de campo linearizadas numa versão tridimensional do gauge de Teyssandier, e a partir desta encontra-se a solução geral no caso de uma fonte pontual estática. Esta métrica se assemelha à métrica quadridimensional relativa a uma corda cósmica reta com simetria de gauge do tipo U(1). Existe uma força gravitacional atuando sobre uma partícula teste movendo-se em baixa velocidade, o que não acontece no contexto da relatividade geral em (2 + 1)D, e raios luminosos sofrem deflexão gravitacional. Considera-se também as mudanças que ocorrem quando um termo topológico de Chern-Simons é adicionado à gravitação quadrática em (2 + 1)D. Acha-se que o inofensivo modo escalar massivo da última, dá origem a um problemático ghost massivo de spin O, enquanto que o ghost massivo de spin 2 é substituído por duas partículas físicas massivas, ambas de spin 2 / Abstract: Quadratic gravity in (2 +1)D, unlike three-dimensional Einstein's gravity, is locally nontrivial and has an extremely well-behaved potential. Here we consider this theory. The general solution of the linearized field equations in a three-dimensional version of the Teyssandier gauge is obtained, and from that the solution for a static pointlike source is found. This metric greatly resembles the four-dimensional metric of a straight U(1)-gauge cosmic string in the framework of linearized quadratic gravity. It is found that a gravitational force is exerted on a slowly moving test particle, a feature not present in general relativity in (2 + 1)D. The deflection of light rays is analyzed as well. We also consider the changes that occur when a topological Chern-Simons term is added to quadratic gravity in (2 + 1)D. It is found that the harmless massive scalar mode of the latter gives rise to a troublesome massive spin-0 ghost, while the massive apin-2 ghost is replaced by two massive particles both of spin-2 / Doutor

Made available in DSpace on 2014-06-11T19:32:10Z (GMT). No. of bitstreams: 0 Previous issue date: 2002-11Bitstream added on 2014-06-13T19:42:32Z : No. of bitstreams: 1 azeredo_ad_dr_ift.pdf: 316259 bytes, checksum: b4ba597ae1ef380cae2698c4e75b0737 (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / A gravitação quadrática em (2 + 1)D, ao contrário da gravitação tridimensional de Einstein, é localmente não trivial e possui um potencial extremamente bem comportado. Analisa-se esta teoria neste trabalho. Obtém-se a solução geral das equações de campo linearizadas numa versão tridimensional do gauge de Teyssandier, e a partir desta encontra-se a solução geral no caso de uma fonte pontual estática. Esta métrica se assemelha à métrica quadridimensional relativa a uma corda cósmica reta com simetria de gauge do tipo U(1). Existe uma força gravitacional atuando sobre uma partícula teste movendo-se em baixa velocidade, o que não acontece no contexto da relatividade geral em (2 + 1)D, e raios luminosos sofrem deflexão gravitacional. Considera-se também as mudanças que ocorrem quando um termo topológico de Chern-Simons é adicionado à gravitação quadrática em (2 + 1)D. Acha-se que o inofensivo modo escalar massivo da última, dá origem a um problemático ghost massivo de spin O, enquanto que o ghost massivo de spin 2 é substituído por duas partículas físicas massivas, ambas de spin 2 / Quadratic gravity in (2 +1)D, unlike three-dimensional Einstein's gravity, is locally nontrivial and has an extremely well-behaved potential. Here we consider this theory. The general solution of the linearized field equations in a three-dimensional version of the Teyssandier gauge is obtained, and from that the solution for a static pointlike source is found. This metric greatly resembles the four-dimensional metric of a straight U(1)-gauge cosmic string in the framework of linearized quadratic gravity. It is found that a gravitational force is exerted on a slowly moving test particle, a feature not present in general relativity in (2 + 1)D. The deflection of light rays is analyzed as well. We also consider the changes that occur when a topological Chern-Simons term is added to quadratic gravity in (2 + 1)D. It is found that the harmless massive scalar mode of the latter gives rise to a troublesome massive spin-0 ghost, while the massive apin-2 ghost is replaced by two massive particles both of spin-2