Left-handed Properties Research Articles

MAGNETIC PROPERTIES OF S-SHAPED SPLIT-RING RESONATORS

We present a theoretical analysis of the radiation of an S-shaped split ring resonator (S-SRR) for the realization of a metamaterial exhibiting left-handed properties. It is shown that the structure is resonant due to its internal capacitances and inductances, which can be adjusted such that the electric plasma frequency and magnetic plasma frequency, both due to the S-SRR only, appear within the same frequency band. Using the same idea, we also present some extended S-shaped split-ring resonator structures with improved performance.

Left-handed materials composed of only S-shaped resonators

We analyze an S-shaped inclusion for the realization of metamaterials exhibiting left-handed properties. Unlike most of the conventional inclusions used so far that are composed of two separate geometries-typically a split ring and a rod-the inclusion proposed in this paper is made of only one S-shaped element which yields an overlapping negative permittivity and negative permeability response over a frequency band of about 2.6 GHz. By adopting this geometry, we manage to lower the negative permittivity frequency band down to the level of the negative permeability frequency band, thus allowing the overlapping to occur. Therefore, the structure works as a stand alone and does not require the use of an additional rod. A theoretical analysis is carried out to study this inclusion and numerical simulations, as well as a Snell refraction experiment, clearly show that the material indeed exhibits a negative index of refraction at some frequencies. The simple pattern of the inclusion, the wide left-handed frequency band exhibited, and the low losses measured indicate the superiority of this inclusion in the realization of left-handed metamaterials.

Metamaterial exhibiting left-handed properties over multiple frequency bands

We present experimental measurements at microwave frequencies of a double band left-handed metamaterial. The sample of metamaterial is composed of an extended version of the S-shaped resonators that exhibit simultaneously a negative permittivity and a negative permeability response at comparable frequencies. The experimental results clearly show that there exist two frequency bands where the refraction index is negative. The double left-handed passbands are due to the multiple capacitances and inductances induced in the structure, which can be further tuned to realize a metamaterial with multiple (more than two) left-handed frequency bands.

Left-handed material containing spherical and nonspherical metallic and magnetic particles

We investigate a composite medium consisting of two types of dispersive particles. By invoking the effective medium approximation both the effective permittivity and permeability are derived separately in the limit of the long wavelength, and thus the effective refractive index can be obtained. We realize the left-handed property of the composite characterized by the negative effective index through the suitable control of the volume fraction. Then, we pay attention to the effective refractive index of the composite material consisting of two components with different shape in the low frequency limit. Numerical results show that the shape of granular inclusions has a large influence on the effective refractive index, and the oblate ellipsoid will be more useful for preparing the left-handed material than the spherical one. Moreover, by adjusting the shape of granular inclusions, a transition of the material properties between the left- and right-handed can be realized.

Beam shifting experiment for the characterization of left-handed properties

In this article, we report experimental results on the shift of a beam that propagates through a slab of metamaterial, known to exhibit left-handed properties. A similar experiment with a Teflon sample of similar size is also carried out for comparison. The results show the existence of a frequency band over which the shift experienced by the beam exceeds the theoretical limit above which the material is left handed. This demonstrates the effectiveness of using a beam shift experiment to characterize the left-handed properties of metamaterial.

Possible existence of left-handed materials in metallic magnetic thin films

In this work, we have theoretically investigated the high-frequency response of fully magnetized metallic magnetic films with magnetization perpendicular to the film surface. We have found that these magnetic films may exhibit left-handed characteristics in the frequency range between ω 0 and ω up when an incident right circularly polarized electromagnetic wave is parallel to the magnetization direction. The upper frequency limit ω up is inversely proportional to the ferromagnetic damping coefficient α. There also exists a critical value of α c, above which the left-handed properties disappear completely. The left-handed properties are manifested with a jump in transmission coefficient, which can be detected when the thickness of the film is less than hundreds of nanometers.

T-junction waveguide experiment to characterize left-handed properties of metamaterials

The left-handed property of a metamaterial is demonstrated by measuring the power at the output of a T-junction waveguide loaded with a metamaterial having one edge cut at 45° with respect to the waveguide axis. Both experimental scattering data and numerical results are presented. The metamaterial sample is realized by using a periodic arrangement of wires and split-ring resonators, and the operating frequency is chosen to correspond to a refraction index of about −1. The results show that when the T junction is empty, most of the power is received at the output port directly facing the input port, whereas when it is loaded with the sample of metamaterial, most of the power is received at the output port perpendicular to the input axis. This indicates that the energy is bent by the oblique edge of the sample by an angle of −45° with respect to the normal, which suggests a negative index of refraction.