Metamaterials Demonstrating Focusing and Radiation Characteristics Applications.

摘要

This dissertation presents theoretical study and numerical evaluation of metamaterials demonstrating near-field focusing and radiation characteristics. We start with physical configuration and performance modeling of all-dielectric metamaterials to develop desired (+/-epsilon, +/-mu) by creating electric and magnetic resonant modes. Arraying these dipole moments can lead to required material properties. Dielectric particles have the potential to offer both electric and magnetic dipole modes. We examine dielectric disks and dielectric spheres as the great candidates for establishing the dipole modes (metamaterial alphabet), and we demonstrate that a structure constructed from unit-cells of two different spheres (or disks), where one set of them develops electric modes, and the other set establishes magnetic modes can provide double negative (DNG) metamaterials. Then some novel applications of metamaterials are investigated. The concept of high resolution focusing of negative index materials is investigated and their performance is compared with those for structures made based on the idea of coupled surface-modes layers. The resonance performance of an electrically small-size radiator made of Epsilon Negative (ENG) material is studied next. It is demonstrated how the material polarization can successfully provide resonance radiation at the negative material constitutive parameters. One of the possible applications of plasmonic materials is to build antenna devices radiating and receiving electromagnetic energy at optical frequencies. Design and fabrication of optical antennas with prescribed spatial patterns is an interesting and challenging task. Based on the concept of scattering resonance of plasmonic particles, we illustrate the concept of a re°ectarray nanoantenna implemented in optics with the use of array of core-shell dielectric-plasmonic materials, each of them optimized properly to achieve the required phase shift. We further present several designs of optical nanoantennas arrays composed of parasitic plasmonic dipoles and loops where they can enhance radiation characteristics and direct the optical energy successfully.