I. Introduction
We treat here an important wave phenomenon, the surface wave. It occurs in many physical systems both mechanical and electromagnetic. Mechanical surface waves can exist at the interface between two media with different densities such as the oceans and air. Ordinary sea waves and tsunamis are surface waves. Seismic events can produce both longitudinal and shear waves at the earth’s surface, resulting in earthquakes. Electromagnetic surface waves can occur at the interface between dielectric and con-ductive media or between two dielectrics satisfying appropriate boundary conditions. Air–salt water or glass–metal interfaces support electromagnetic surface waves. Here we focus on electromagnetic waves at the interface between common dielectrics and noble metals, such as air or glass and silver or gold, respectively. We will characterize these waves by their distinctive properties of dispersion, spatial field distribution, and polarization. These properties will be used to analyze useful phenomena such as wave guiding within subwavelength structures and spatial light localization below the diffraction limit.
II. Definition of Surface Wave
A Surface wave is a mechanical wave that propagates along the interface between differing media, usually two fluids with different densities. A surface wave can also be an electromagnetic wave guided by a refractive index gradient. In radio transmission, a ground wave is a surface wave that propagates close to the surface of the Earth.
Surface wave is a wave in which particles of the medium undergo a circular motion. Surface waves are neither longitudinal nor transverse. In longitudinal and transverse waves, all the particles in the entire bulk of the medium move in a parallel and a perpendicular direction (respectively) relative to the direction of energy transport. In a surface wave, it is only the particles at the surface of the medium that undergo
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