Donald W. Forester

Scattering properties of an impedance-matched, ideal, homogeneous, causal “left-handed” sphere

The plane-wave scattering properties of a sphere of material having an ideal, homogeneous, and causal permittivity epsilon(f), and permeability mu(f) were investigated through detailed three-dimensional finite-difference time-domain, method-of-moments, and series-solution simulations. A Lorentzian functional form was chosen for epsilon(f) and mu( f), as it yields causal responses and allows us to study the physics of the left-handed-medium (LHM) regime. Our interest lies mainly in the frequency range where negative refraction [Re(n) < 0] is observed. We found that when operating in the LHM regime, an impedance-matched sphere responds with scattering features strikingly different from those found in ordinary materials. In particular, we found zero back-scattering and forward scattering that exceeds that of a metal sphere of similar size. The equality of E- and H-plane patterns was proved analytically and numerically, and the possibility of internal subwavelength focusing with a zero index sphere is also reported.

Rough ocean surface and sunglint region characteristics

The sunglint geometrical optics equations of a statistically faceted sea, supported by the so-called interaction probability density and employing an averaging hybrid of the Cox-Munk and Mermelstein slope statistics, was successful in simulating 0.5 microm sunglint region characteristics. The results match independent experimental data, and good agreement is reported for various sea conditions and Sun locations, on sunglint amplitude, sunglint location, and azimuth range. In particular, the peak reflectance shift from the specular direction toward the horizon is correctly predicted, and it is found that the physical mechanism responsible for the shift is the accumulation of contributing facets near the horizon.

Exact solution to plane-wave scattering by an ideal "left-handed" wedge.

An exact analytical solution to the problem of plane-wave diffraction by a penetrable left-handed medium (LHM) epsilon = micro = -1 wedge of arbitrary angle (subject to valid physical constraints) is presented. Standard analysis involving discontinuous angular eigenfunctions and even/odd symmetry decomposition resulted in a discrete spectrum leading to a series solution resembling the traditional perfect electric conductor wedge solution but exhibiting the expected negative refraction phenomenology. Numerical results are presented, some of which seemed paradoxical but are explainable by classical means. A new type of illusory edge radiation is observed and explained. Also, a novel edge-launched interface standing wave is observed on the directly illuminated side. The exact analytical solution is verified by comparison with finite-difference time-domain simulation on causal LHM materials.

Bandpass left-handed material optical filter with enhanced stop band rejection

It is shown that a layer of left-handed media can act as a bandpass filter with a roll factor that far exceeds those of state-of-the-art spectral filters. The conditions for enhanced stop band rejection are presented and are deemed feasible, as the models used correspond to physically realizable materials. Roll factors of the order of 10(4)-10(6) dB/GHz are found, together with acceptable insertion losses of the order of 10 dB.