We investigate numerically the limits of the resonant magnetic response with a negative effective permeability ${\mu }_{\mathrm{eff}}$ for single-ring multicut split-ring resonator (SRR) designs up to optical frequencies. We find the breakdown of linear scaling due to the free electron kinetic energy for frequencies above $\sim 100\mathrm{THz}$. Above the linear scaling regime, the resonance frequency saturates, while the amplitude of the resonant permeability decreases, ultimately ceasing to reach negative value. The highest resonance frequency at which ${\mu }_{\mathrm{eff}}<0$ increases with the number of cuts in the SRR. A $LC$ circuit model provides explanation of the numerical data.

We study both theoretically and experimentally the transmission properties of a lattice of split ring resonators (SRRs) for different electromagnetic (EM) field polarizations and propagation directions. We find unexpectedly that the incident electric field E couples to the magnetic resonance of the SRR when the EM waves propagate perpendicular to the SRR plane and the incident E is parallel to the gap-bearing sides of the SRR. This is manifested by a dip in the transmission spectrum. A simple analytic model is introduced to explain this interesting behavior.

We demonstrate experimentally and numerically that metamaterials based on bilayer cross wires give giant optical activity, circular dichroism, and negative refractive index. The presented chiral design offers a much simpler geometry and more efficient way to realize negative refractive index at any frequency. We also developed a retrieval procedure for chiral materials which works successfully for circularly polarized waves.

We present results for acoustic wave propagation in periodic composites consisting of solid spheres in a fluid host. We show that for solid scatterers in fluid host material combinations the extensively used plane-wave method is inadequate to produce accurate results and a new approach is required. Our band-structure results are obtained by using a multiple-scattering approach based on an extension of the well-known Korringa-Kohn-Rostoker method.

We investigate, both theoretically and experimentally, a left-handed metamaterial design composed of pairs of short slabs connected with continuous wires, operating in microwave frequency regime. The design was found to give left-handed behavior for a wide range of structure parameters, maintaining high impedance match with free space. We introduce a capacitor-inductor circuit description of the design and we show that this description can account for all the characteristics of its electromagnetic behavior, explaining also its superior performance.