N. T. Tung

Dependence of the distance between cut-wire-pair layers on resonance frequencies

We studied both experimentally and theoretically the influence of the distance between adjacent cut-wire-pair layers on the magnetic and the electric resonances in the microwave-frequency regime. Besides the dependence on the separation between cut-wire pairs, along the electric-field direction, the electric resonance strongly depends on the distance between cut-wire-pair layers, while the magnetic resonance is almost unchanged. This contrast can be understood by the difference in the distribution of induced-charge density and in the direction of the induced current between the electric and magnetic resonances. A simple model is proposed to simulate our experimental results and the simulation results are in good agreement with the experiment. This result provides important information in obtaining left-handed behavior when the cut-wire pairs are combined with the continuous wire.

Single- and double-negative refractive indices of combined metamaterial structure

We experimentally and numerically studied the transmission spectra of a combined metamaterial structure whose negative refractive index was supposed to be achievable only with simultaneously negative permittivity and permeability. However, it was found that the negativity of the refractive index of such a structure could be obtained not only when both parameters were negative but also when only one parameter, more specifically the permittivity was negative. These characteristics of combined structure were analyzed in detail by using the standard retrieval effective-medium method. According to the analyses, it can be concluded that the negativity originates from the complex permittivity and permeability. The interplay among the real and the imaginary parts of those parameters is the key to the negative behavior of refractive index.

Influence of lattice parameters on the resonance frequencies of a cut-wire-pair medium

We studied both theoretically and experimentally the influence of the lattice constant on the resonance frequencies of cut-wire-pair structures, which are essential components in assembling left-handed materials. These structures were designed and fabricated, and the transmission spectra were measured in the microwave-frequency regime. Numerical simulation was performed using the transfer-matrix method. All the numerical results were in good agreement with the experimental data. It was found that the lattice parameters of the cut-wire-pair structure provide sensitive effects on the electric resonance, especially, in the propagation k and the electric field E directions, while the magnetic resonance frequency is nearly unchanged, except for its bandwidth and depth. In addition, we also studied the effect of dielectric layer thickness on the resonance frequencies of the cut-wire-pair structure. These sensitive changes in the electric resonance might have remarkable effects on the effective plasma frequency ...

Left-handed transmission in a simple cut-wire pair structure

It is well known that, together with the plasma behavior of continuous wires, the use of cut-wire pair as a metamagnetic component is to drive the negative permeability in the left-handed combined structure. In this study, we have investigated a strange left-handed transmission in a metamaterial consisting of only conventional cut-wire pair structure without additional adjustment. It is shown that the observed left-handed behavior, which occurs at a frequency three times higher than that for the combined structure, originates from the fundamental negative permittivity provided by the symmetric resonant mode and a negative permeability by the third-order asymmetric resonance. Our results would simplify extremely the fabricating procedure, especially, for terahertz regime as well as reveal many possibilities to design optical devices based on the electromagnetic responses of cut-wire structure.

Effect of the dielectric layer thickness on the electromagnetic response of cut-wire-pair and combined structures

This report investigates the effect of the dielectric layer thickness on both magnetic and electric resonances of cut-wire-pair (CWP) structures in the microwave frequency regime. It was found that the resonances are sensitive to the thickness of the dielectric layer. As the thickness increases, the bandwidth of the magnetic resonance is slightly extended to a higher frequency, while the low-frequency edge of the electric-resonance band is remarkably shifted to a lower frequency. It was also found that the dependence of the magnetic resonance frequency on the dielectric layer thickness follows the trend of the closed formula based on the cavity model for the coupled metallic elements (Cai et al 2007 Opt. Express 15 3333). In addition, we also studied the effect of the dielectric layer thickness on the left-handed behaviour of a combined structure consisting of CWP and continuous wire. The actual measurements are compared with the numerical simulation values to show a good coincidence.

Effects of the Electric Component on Combined Metamaterial Structure

In this report, we experimentally and numerically studied the transmission spectra of combined metamaterial structure which consists of cut-wire pairs and continuous wires. The effective permittivity and permeability were extracted from the complex scattering parameters utilizing the standard retrieval procedure. By examining the influence of the width of continuous wires, we were able to investigate the important role of electric response for the left-handed transmission. It is found that the changed electric component either enhances or even destroys the left-handed behavior of combined structure. Our experimental and numerical results expand the understanding on the electromagnetic behavior of combined metamaterial structure.

Demonstrate the Double Negative Behavior of Metamaterial Using the Effective Medium Theory

We fabricated the electric and magnetic metamaterial, and measured their transmission spectra. The electromagnetic response of the combined structure, which consists of cut-wire pair and continuous wire, are experimentally and numerically studied in the microwave frequency regime. The simulations are performed in a qualitative agreement with experiment utilizing the transfer-matrix method. The double negative behavior of combined structure is observed and demonstrated using the effective medium theory.

Metamaterials: Detailed parametric studies on cut-wire pair and combined structure

We studied the electromagnetic behavior of cut-wire pair structure, which is considered as a magnetic metamaterial for designing the left-handed material. It was found that the lattice constant of cut-wire pair structure provides subtle effects not only on the electric resonance but also on the magnetic one. In addition, we also investigated on how this affects the left-handed behavior of combined structures of cut-wire pair and continuous wire. These structures were designed, fabricated, and measured in the microwave frequency regime.

Influence of structural parameters on the resonance frequencies of cut-wire pair

We studied the influence of structural parameters on the resonance frequencies of cut-wire pair, which are the essential components for designing the left-handed materials. It was found that the structural parameters of cut-wire pair structure provide subtle effects on not only the magnetic resonance but also the electric one. The results are good agreement with the previous theoretical studies. These structures were designed, fabricated, and measured in the microwave frequency regime.