Omnidirectional Surface Guided Modes And Imaging Properties In Single Negative Materials

The double negative material (DNM) is a kind of metamaterial with both negative permittivity and negative permeability. As the plane waves propagate in such materials, the electric field ( E ), the magnetic field ( H ) and the wave vector ( k ) satisfy the"left-handed"principle and so that such material is called"left-handed"medium (LHM). The DNM has such peculiar optical properties as waveguide, superlens, the atenna , the transparency of the electromagnetic waves and so on. Such materials with only permittivity or only permeability, are called single negative (SNG) materials. These materials include the epsilon-negative (ENG) media, in which the permittivity is negative, but the permeability is positive, and the mu-negative (MNG) media, in which the permeability is negative, but the permittivity is positive. The SNG materials have attracted much attention due to their peculiar properties. The bilayer of SNG materials are constructed as an effective DNM. When the SNG materials are paired together, such interesting properties as resonances, transparency, anomalous tunneling, and zero reflection are found. The one-dimensional photonic crystals made up of SNG materials can form a new kind of photonic band gap, which is very strong. Such ENG materials as bulk metal and metal-dielectric composites are able to break through the conventional diffraction limit, and thus realize the subwavelength imaging. The multilayered structure containing these ENG materials can not only image the source far away from the imaging plane, but also achieve the imaging quality enhancement in a large degree.In this thesis, we concentrate on the optical properties of the symmetric waveguide containing the one-dimensional photonic crystals formed by single-negative materials and the imaging properties of composites. The thesis is organized as follows:1 The optical properties of the symmetric waveguide containing the one-dimensional photonic crystals formed by single-negative materials. We employ both the transfer matrix method (TMM) and the effective medium approximation (EMA) to investigate the guided modes in an air-core layer, which is sandwiched by the one-dimensional photonic crystal with alternate single-negative materials, respectively. The theoretical results show that there are two branches of omnidirectional guided modes around two certain frequencies. Within the framework of effective medium approximation (EMA), the two frequencies are found to correspond to the zero-average-volume-permittivity frequency and the zero-average-volume-permeability frequency , respectively. We have predicted that both the symmetric and antisymmetric surface guided modes are supported within this system. Moreover, this kind of surface guided modes have low group velocity.2 Imaging properties of a superlens based on metal-dielectric composites of nonspherical particlesWe mainly study the subwavelength imaging with a superlens, produced by using an isotropic metal-dielectric composites of nonspherical particles and focus on the investigation of effects of the particles' shape on the imaging properties of the superlens. It is found numerically that, (i) The operational point can be blue-shifted to the optical range by tuning the particles'shape, which is very important in experiments. (ii). The operational wavelength range is able to be widened by the suitable adjustment of the particles'shape. (iii). Tuning the shape of particles is an alternative way to produce the tunable superlens; (iv). An enhanced imaging quality of the superlens can be achieved by the suitable adjustment of the particles' shape. Moreover, we estimate the analytical expression of the subwavelength resolution of the superlens to show that the suitable adjustment of the particles'shape and the metal filling factor is responsible for a better subwavelength resolution. It is also found that an enhanced imaging resolution can be obtained by using a multilayered structure with alternate metal-dielectric composites and host medium. The thinner the layer width, the better subwavelength imaging is achieved.3 Tunable negative refraction and imaging properties of the metal-dielectric compositesThe theoretical results show that the metal-dielectric composite is able to realize the tunable negative refraction by the adjustment of the metallic particles'shape. The tunable slab lenses based on such composites are helpful to realize subwavelength imaging. Moreover, when the particles'shape approaches the needle shape or the plate shape, good imaging quality is achieved.3 Imaging properties of a multilayered structure composed of metal-dielectric compositesWe study a multilayered structure, composed of metal-dielectric composites, which can be modeled as the metamaterials with anisotropic dielectric permittivity. Subwavelength imaging can be achieved within this structure when the principal components of the effective permittivity (εex,εez) have the opposite signs. Since the components of the effective dielectric permittivity are dependent on the shape of particles and the incidental wavelengths, a better subwavelength resolution is able to be achieved by the suitable adjustment of these two physical quantities . In addition, the imaging enhancement is improved by decreasing the layer thickness.