Theoretical and experimental study on electromagnetic surface modes in structured metal surfaces in microwave region

Abstract

This dissertation presents basic studies on the propagation properties of the electromagnetic surface modes generated on structured metal surfaces to investigate the possibility of controlling the flow of surface modes for device applications. In the frequency range from roughly DC up to 10 terahertz, normal metals which support little surface plasmon polaritons can be considered as perfect electric conductors. In this regime, structured metal surfaces support different types of surface bound states according to the geometry of surface corrugation. Signals are carried by these surface modes as coupling between the incident electromagnetic waves and the electro-magnetic resonance modes or waveguide modes in individual metallic structures which compose the structured metal surfaces.

The diffraction theory and effective medium theory are employed to analyze the three types of structures on perfect metal surfaces: one-dimensional grooves, two-dimensional arrays of rods and of holes. In the three cases, it is known that these structures support electromagnetic surface modes and the dispersion relations of these modes have similarities with the dispersion relations of effective mediums. The dispersion relations of surface modes in one-dimensional grooves and two-dimensional arrays of rods are similar to those of waveguide modes in anisotropic dielectric slabs. Also, the two-dimensional array of holes has dispersion relations similar to those of surface plasmon polaritons on a metal-dielectric interface in optical region, that is the reason why surface modes in this structure is called `spoof surface plasmons (SSPs)`. Also, the finite-difference time-domain (FDTD) simulations support the results of these theoretical models. Additionally, we explore that their electromagnetic responses in these structures as metamaterials can be engineered by controlling the geometrical parameters defining the structured surfaces.

To investigate the properties of surface modes, expe...