Free-standing THz electromagnetic metamaterials.

Using micromanufactured S-shaped gold strings suspended in free space by means of window-frames, we experimentally demonstrate an electromagnetic meta-material (EM(3)) in which the metallic structures are no longer embedded in matrices or deposited on substrates such that the response is solely determined by the geometrical parameters and the properties of the metal. Two carefully aligned and assembled window-frames form a bi-layer chip that exhibits 2D left-handed pass-bands corresponding to two different magnetic resonant loops in the range of 1.4 to 2.2 THz as characterized by Fourier transform interferometry and numerical simulation. Chips have a comparably large useful area of 56 mm(2). Our results are a step towards providing EM(3) that fulfill the common notions of a material.

Multi-frequency resonator based on dual-band S-shaped left-handed material.

In this paper, we experimentally realize a one-dimensional RHM (Right-handed Material)-LHM (Left-handed Material) multi-frequency resonator that consists of a dual-negative-band LHM and air arranged in an X-band waveguide. Multi-resonant frequencies are observed within two left-handed bands of the LHM. The effects of the loss and the hyperbolic dispersion relation of LHM layer are discussed. The incorporation of such a LHM into the resonator design allows more flexibility to realize multi-resonance.

Power propagation in homogeneous isotropic frequency-dispersive left-handed media.

We study transmission at a boundary between a right-handed medium (RHM: epsilon>0, mu>0) and a frequency dispersive left-handed medium [LHM: epsilon(omega)<0, mu(omega)<0 for some omega], both homogeneous and isotropic. In order to account for the dispersion, two types of signal spectra are considered. The first consists of two discrete frequencies, while the second is Gaussian. Explicit expressions for the time-domain fields are obtained, from which the time-averaged Poynting vectors and hence power flow vectors are calculated. In both cases, we find that waves refract at negative angles at a RHM-LHM interface.

Scattering of electromagnetic waves from dense distributions of spheroidal particles based on Monte Carlo simulations.

In a dense discrete random medium, the propagation and scattering of waves are affected not only by the individual properties of the particles such as size, shape, and permittivity, but also by group properties such as the statistics of relative particle positions and relative orientations. We use Monte Carlo simulations to investigate the interactions of electromagnetic waves with a dense medium consisting of spheroidal particles for cases of random orientation and for cases of aligned orientation. A shuffling process is used to generate the positions of densely packed spheroids. Multiple-scattering equations are formulated by means of the volume integral equation and are solved numerically. The scattering results are averaged over realizations. Numerical results are presented for the extinction rates and the phase matrices. Salient features of the numerical results indicate that (1) the extinction rates of densely packed small spheroids are smaller than those of independent scattering; (2) for aligned spheroids, the extinction rates are polarization dependent; and (3) the co-polarized part of the phase matrix for densely packed spheroids is smaller than that of independent scatering, while the cross-polarized part is larger than that for independent scattering. This means that the ratio of cross-polarization to co-polarization is significantly higher than that of independent scattering.