Scattering of light in the presence of nano-structured materials, i.e. with features in the order of the wavelength of the light or smaller, reveals details of how light interacts with matter at... Show moreScattering of light in the presence of nano-structured materials, i.e. with features in the order of the wavelength of the light or smaller, reveals details of how light interacts with matter at the nanoscale. In this dissertation we present four cases of light scattering on nano-structures. First we describe how light confined in 2D structures, namely a dielectric membrane and a metal layer, interacts with either a single nano-hole or a hole-array. Then, we study two cases of light propagating in random scattering media: we show how phase modulation can be used to measure scattering properties in a volume scatterer (e.g. white paint), and we investigate light transport in a rough thin-film silicon solar cell. Show less
Gold nanorods are ideal candidates for complementing fluorophores in labelling applications. The presence of the surface plasmon resonance generates large absorption and scattering cross sections,... Show moreGold nanorods are ideal candidates for complementing fluorophores in labelling applications. The presence of the surface plasmon resonance generates large absorption and scattering cross sections, thus making the detection of single nanoparticles possible under a light microscope. The plasmon of gold nanorods depends on the ratio between their width and length and covers the range between 540nm for spheres and even above 800nm for elongated particles, thus almost the entire visible and near-infrared spectrum. The surface plasmon presents great opportunities in (bio-)sensing, enhanced spectroscopies, photothermal therapy and for concentrating light below the diffraction limit. Show less
A surface plasmon is light that is bound to a metal surface. The main merit of a surface plasmon is that is provides confinement below the diffraction limit. In this thesis, we first study the... Show moreA surface plasmon is light that is bound to a metal surface. The main merit of a surface plasmon is that is provides confinement below the diffraction limit. In this thesis, we first study the excitation and scattering of surface plasmons by subwavelength holes in the metal. Thereafter we show that an array of these hole acts as a surface plasmon laser when the surface plasmons are sufficiently amplified using a semiconductor gain medium Show less
This dissertation contains scientific research within the realm of quantum optics, which is a branch of physics. An experimental and theoretical study is made of two-photon interference phenomena... Show moreThis dissertation contains scientific research within the realm of quantum optics, which is a branch of physics. An experimental and theoretical study is made of two-photon interference phenomena in various optical systems. Spatially entangled photon pairs are produced via the nonlinear optical process of spontaneous parametric down-conversion. These entangled photons are then passed through different optical systems to study various aspects of two-photon interference. Firstly, an experimental analysis is made of the high-dimensional entanglement that is present in the orbital angular momentum of the photons. Secondly, we present a comprehensive description of two-photon quantum interference behind a double slit. We demonstrate how to control the quantum correlations and present the first observations of complete two-photon diffraction patterns behind a double slit. Finally, we present pioneering experiments on spatially entangled two-photon states that are scattered of random media. We have observed and theoretically analyzed the structure in the random two-photon interference patterns called two-photon speckle patterns. Spatial entanglement gives two-photon speckle a much richer structure than ordinary one-photon speckle. Our experiments also demonstrate a two-photon interference phenomenon that survives averaging over different realizations of disorder. The latter results are closely related to bosonic, fermionic, and anyonic particle exchange symmetries. Show less
The study of gas-surface interaction dynamics is important both for the fundamental knowledge it provides and also to aid the development of applications involving processes such as sputtering,... Show moreThe study of gas-surface interaction dynamics is important both for the fundamental knowledge it provides and also to aid the development of applications involving processes such as sputtering, plasma etching and heterogeneous catalysis. Elementary steps in the interactions, such as chemical reactions, adsorption and scattering are prototypical of more complex processes and better understanding of them deepens our knowledge of such processes. In addition, experimental measurements of specific interactions can be used to validate advanced computer models. Hence the experiments in this thesis have been carried out under well-defined condition, namely in ultrahigh vacuum and using high-purity single-crystal samples. The thesis is primarily focussed on understanding the interaction of hyperthermal Ar and N (~4-6 eV) with Ru(0001) and Ag(111) via scattering studies. Ar is very inert and its interaction with surfaces is primarily repulsive in nature, while N atoms probe the surface chemisorption well. From the study of Ar scattering dynamics, surface properties have been probed. From N scattering studies, chemisorption dynamics have been investigated. It is found that the electronic state of the incident particle may play an important role in the gas-surface interaction. Separately, the influence of pre-adsorbed CO on Ru(0001) on D2 dissociation have been unravelled. Show less
The theoretical foundation for the work reported here is provided by Landauer's scattering theory of electron transport. The three main ingredients of a scattering problem are (1) a set of... Show moreThe theoretical foundation for the work reported here is provided by Landauer's scattering theory of electron transport. The three main ingredients of a scattering problem are (1) a set of reservoirs that emit and absorb particles, (2) the particles themselves, that propagate as waves between the reservoirs and (3) a scatterer that obstructs free propagation. In this thesis two classes of problems are considered. The first class results when the physical quantities characterizing the reservoirs or the scatterer are not constant in time. The second class results when wave propagation is described by the Dirac equation rather than the Schroedinger equation, as is the case in a 2D form of carbon, called graphene. Show less
The initial goal of this thesis was to demonstrate chaos in an open two-mirror resonator. We have designed a bifocal mirror that forms a resonator with an unstable inner and a stable outer part. To... Show moreThe initial goal of this thesis was to demonstrate chaos in an open two-mirror resonator. We have designed a bifocal mirror that forms a resonator with an unstable inner and a stable outer part. To be able to distinguish phenomena unique for configuration from phenomena also present in conventional resonators, i.e., roughness-induced scattering and aberrations, the performance of a conventional stable resonator is investigated first. Roughness-induced scattering turns out to affect the cavity finesse as well as the average power throughput and produces mode coupling close to frequency-degenerate points. We demonstrate, furthermore, a method to accurately determine aberrations by measuring the Gouy phase of subsequent higher-order modes around frequency-degeneracy. The bifocal mirror is not fabricated by traditional grinding and polishing, but by diamond-machining. The eigenmodes of a resonator with one diamond-machined bifocal mirror turn out to be Laguerre-Gaussian. We demonstrate furthermore, the coupling of two resonators based on transmission spectra and patterns, and report on the ability of the configuration to fulfill the basic requirements to obtain chaos. Show less
