Lateral Electromagnetic Waves Research Articles

Generation of surface plasmon-polaritons by edge effects

By using numerical and analytical methods, we describe the generation of fine-scale lateral electromagnetic waves, called surface plasmon-polaritons (SPPs), on atomically thick, metamaterial conducting sheets in two spatial dimensions (2D). Our computations capture the two-scale character of the total field and reveal how each edge of the sheet acts as a source of an SPP that may dominate the diffracted field. We use the finite element method to numerically implement a variational formulation for a weak discontinuity of the tangential magnetic field across a hypersurface. An adaptive, local mesh refinement strategy based on a posteriori error estimators is applied to resolve the pronounced two-scale character of wave propagation and radiation over the metamaterial sheet. We demonstrate by numerical examples how a singular geometry, e.g., sheets with sharp edges, and sharp spatial changes in the associated surface conductivity may significantly influence surface plasmons in nanophotonics.

The detection of dielectric spheres submerged in water

The basic theory is developed for the use of lateral electromagnetic waves to detect dielectric spheres submerged in fresh or salt water or human flesh. The source and receiver are, respectively, center-driven and center-loaded eccentrically insulated dipoles. A numerical example is computed to determine the magnitude of the scattered field that must be detected.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Lateral electromagnetic waves and pulses on open microstrip

The propagation of lateral electromagnetic waves and pulses on microstrip is investigated. Interference patterns generated by the superposition of the lateral and direct waves along the air-substrate surface are shown. The field generated by the pulse excitation of a horizontal dipole on the air-substrate boundary is shown to consist of a lateral-wave pulse and a slower direct-wave pulse. Their differences in shape and decay rate are clarified. It is shown that the shape of a Gaussian pulse propagating along an open microstrip transmission line is closely related to the shape of the lateral electric-field pulse generated by a Gaussian current pulse in a dipole on the air-substrate boundary. >

Lateral electromagnetic waves from a horizontal antenna for remote sensing in the ocean

The properties of lateral electromagnetic waves on the one hand and antennas in material media on the other are applied to the problem of locating a submerged submarine from measurements of the scattered field observed on the surface of the sea. The method parallels an earlier study on locating a conductor buried in the earth. However, major changes are required because of the quite different properties of the media and the consequent very much lower frequencies. An important improvement is also incorporated in the use of circularly polarized lateral waves. Representative calculations are made to illustrate the relative orders of magnitude of the dimensions and fields involved and the required sensitivity of a receiver.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

On the reflection of lateral electromagnetic waves from perpendicular boundaries

Lateral electromagnetic waves propagate along the boundary between an electrically dense half space (z≥0) with the wave number k1 (earth, water) and a less dense half space (z≤0) with the wave number k2 (‖k2‖2≪‖k1‖2). The scattering of such waves by vertical discontinuities in the denser half space (k1 changes to k3) is analyzed. It is shown that the reflected field is very small even when k3→∞. Also analyzed are the reflections from thin vertical walls of height L of the denser medium projecting vertically into the less dense medium. These are studied specifically when the walls are made of metal. It is shown that reflections are small when k2L≪1, but very significant when k2L&amp;gt;1. The standing-wave patterns due to incident and reflected lateral waves are determined and shown graphically.

Lateral electromagnetic waves along plane boundaries: A summarizing approach

Lateral electromagnetic waves along a plane boundary between homogeneous half-spaces are reviewed. The electromagnetic fields generated by vertical and horizontal electric dipoles near the boundary between air and the earth (salt or fresh water, soil, ice, etc.) are summarized in terms of a new unified theory of lateral-wave propagation. Complete theoretically determined fields are displayed and compared with measured fields at f = 601 MHz relative to the boundary between air and salt water (σ = 3.5 S/m, e r = 80). Near, intermediate, and asymptotic fields are related graphically to the new general theory and to the approximate and restricted formulas of Norton and Banos as well as to the Zenneck wave. Application is made to the specific problem of communication with submerged submarines by means of transmitters consisting of electrically short monopoles in air and horizontal traveling-wave antennas and directional arrays in sea water. The properties of the antennas are evaluated in the frequency range 10 ≤ f ≤ 30 kHz which is optimum for receiver depths near 10 m, and at f = 1 kHz which is optimum for depths up to 50 m. The effects of reflections from the ionosphere and of the earth's curvature are not included.