Electric Plasma Frequency Research Articles

Low-loss near-zero-index metamaterial based on a single board for broadband electromagnetic-wave switches

Zero-index metamaterials have excellent potential for applications in electromagnetic devices, but severely suffering from inadequate bandwidth or high loss. Here we present an easy-fabricating zero-index metamaterial, composed of the wires on the surface and through the substrate. The near-zero-index metamaterial presents a low loss in the wide frequency range from 10.72 GHz to 11.4 GHz. A general approach of low-loss near-zero refraction is proposed based on the relationship between electric plasma frequency and magnetic plasma frequency, which provides an effective way for governing electromagnetic loss of metamaterials. The near-zero-index metamaterial can service as the broadband electromagnetic-wave switch covering the range of 10.5 GHz to 11.54 GHz, with a relative transmission ratio up to 97.8%.

Corrected Drude model of thin circle metal rods’ periodic array

A corrected Drude model is presented for structural electromagnetic performance analysis of metamaterials with thin circle metal rods. The prediction model about periodic array of thin circle metal rods is theoretically derived; and the electric plasma frequency expression and the damping factor expression of Drude model are corrected. The numerical examples show that the modified theoretical prediction model has higher accuracy than other representing models. Then, the great robustness of the corrected Drude model is verified through number examples for different cases; and even the errors for the middle/thick circle rod and the middle square rod are still acceptable. Finally, as a result of the minimum and maximum ratio of the unit cell dimension to the radius, applicable conditions of the corrected Drude model are proposed.

Terahertz Plasmonic Structure With Enhanced Sensing Capabilities

We have designed, fabricated, and experimentally verified a highly sensitive plasmonic sensing device in the terahertz frequency range. For a proof of concept of the sensing phenomenon, we have chosen the so-called fishnet structure based on circular hole array insensitive to the polarization of the incident wave. We employ the localized resonance associated with the cutoff frequency (electric plasma frequency) of the hole array to investigate its sensing capability. A thin-film overlayer deposited on the surface of the metallic apertures causes an amplitude modulation and a shift in the resonant frequency of the terahertz transmission. The frequency shift and the amplitude modulation were investigated as a function of the refractive index and the thickness of the overlayer for determining the sensing potential of the proposed structure. Measurements carried out using terahertz time-domain spectroscopy show good agreement with the numerical predictions. The results we obtained indicate that the proposed device could be very promising for enhancing the sensing capabilities of the refractive index changes involved in bio-applications, for instance.

Dual-band quasi-zero refraction and negative refraction in coin-shaped metamaterial

This paper demonstrates a metamaterial capable of realizing a dual-band quasi-zero refractive index and a negative refractive index, which consists of a coin-shaped slice and two parallel planar wires. The zero refractive index is achieved over a very wide frequency range. The bandwidth of the first band of the quasi-zero index can reach up to 3 GHz, and the width of the second band exhibiting low loss is 0.4 GHz. Between these two bands, the negative refractive index band is 9.0–13.9 GHz. The corresponding formulas of electric plasma frequency and magnetic plasma frequency are established, and the theoretical results agree well with the simulated results. The proposed metamaterial may have potential applications in multiband or broadband devices.

Textile inspired flexible metamaterial with negative refractive index

This work introduces metallo-dielectric woven fabric as a metamaterial for phase-front manipulation. Dispersion diagram as well as effective medium parameters retrieved from reflection and transmission coefficients point out negative values of refractive index. By numerical simulations, it is evidenced that a pair of meandered metallic wires, arranged in a top to bottom configuration, can yield to a textile metamaterial with simultaneously negative permittivity and permeability. While the effective negative permittivity stems from the metallic grid arrangement, resonating current loop resulting from the top to bottom configuration of two meandered metallic wires in near proximity produces magnetic activity with negative permeability. By adjusting the distance between pairs of metallic wires, the electric plasma frequency can be shifted to overlap the magnetic resonance. Finally, it is shown that the woven metamaterial is insensitive to the incident angle up to around 60°.

Possible behaviours of TE modes in a left-handed slab waveguide

We present a theoretical study of a slab waveguide made of a left-handed material in order to clarify the action of electric plasma frequency on the guided dispersion characteristics. We also examined the dispersion properties of the guided waves and discuss the existence of new modes. We show that it is possible to increase the domain of existence of the mode and control the energy flow for a suitable choice of parameters. That leads to an exhibition of new types of modes unusually seen in slab waveguide only composed by right-handed material.

Wave properties of Fibonacci-sequence photonic crystals containing single-negative materials

Electromagnetic wave properties of a Fibonacci-sequence photonic crystal (FSPC) made of single-negative materials are theoretically investigated. It is found that, in the oblique incidence, such a kind of photonic crystal exhibits additional photonic bands or dips in the vicinity of either magnetic plasma frequency or electric plasma frequency. The additional photonic bands or dips corresponding to magnetic plasma frequency occur only for the TE wave, whereas those corresponding to electric plasma frequency occur only for the TM wave. In addition, we find that there exist omnidiretional gaps in such a single-negative FSPC.

DESIGN AND ANALYSIS OF MULTICHANNEL TRANSMISSION FILTER BASED ON THE SINGLE-NEGATIVE PHOTONIC CRYSTAL

In this work, the multiple filtering phenomenon in a photonic crystal made of single-negative (SNG) materials is investigated. We consider a finite photonic crystal (AB)N immersed in air, in which A, B are epsilon-negative (ENG) and mu-negative (MNG) materials, respectively, and N is the stack number. It is found that such a photonic crystal can function as a multichannel transmission filter with a channel number equal to N−1. The required condition is that the thickness of MNG layer must be larger than that of ENG layer when magnetic plasma frequency is greater than electric plasma frequency. The channel frequencies can be red-shifted as the thickness of MNG layer decreases. The channel positions can be tuned by the incidence angle for both TE and TM polarizations. That is, the peak frequency is blue-shifted when the angle of incidence increases. Additionally, the influence of the static permeability of ENG medium and permittivity of MNG medium is also illustrated. The proposed structure can thus be used to design as a tunable multichannel filter which is of technical use in signal processing.

Synthesis of compact and highly selective filters via metamaterial-inspired coplanar waveguide line technologies

In this study, two split ring resonator-based coplanar waveguide cells operating in C-band are studied. Particularly, the lines have been loaded with double shunt strips or series gaps. The use of double strips allows controlling the electric plasma frequency, and at the same time permits one to have a good excitation of the resonators. On the other hand, the employment of double series gaps provides a right-handed behaviour, contrary to conventional metamaterial structures for which a backward propagation is obtained. Several parametric studies show the possibility to significantly increase the selectivity, and in particular the possibility to have an effective control on the out-of-band rejection levels by means of the loading elements characteristics. In a second stage, enhanced out-of-band rejection properties have been obtained by the use of cascaded basic cells and rigorous optimization processes. As a consequence, the proposed filters can be foreseen for practical applications relying on the trade-off found between selectivity, insertion losses and out-of-band rejection.

The Design of Broadband, Volumetric NRI Media Using Multiconductor Transmission-Line Analysis

Multiconductor transmission-line (MTL) analysis is used to model a broadband, volumetric negative-refractive-index (NRI) medium. Equations for the two-dimensional dispersion characteristics and the Bloch impedance are derived using a simplified periodic MTL analysis that provides insight into the operation of the NRI structure, while still accounting for spatial dispersion. Equations for the resonant points of the NRI medium are also derived, including the magnetic and electric plasma frequencies and the low-frequency backward-wave cutoff. The nature of each resonant point is discussed as well. Finally, this paper presents the modeling of finite structures with rigorous MTL analysis. Using this method, the reflection and transmission coefficients for normal incidence on a four-cell slab of the NRI medium are calculated and compared to full-wave simulation.

Numerical investigation of metamaterials infiltrated by liquid crystal

We present a comprehensive analysis of the influence of liquid crystal (LC) molecules' reorientation on the electromagnetic behaviors of S-type left-handed metamaterials (LHMs) by considering an isotropic and anisotropic approach, respectively. It is shown that the frequency shift of the magnetic resonance as a function of the LC molecules' reorientation is reversed with a blue shift for the isotropic case and a red shift for the anisotropic one, the latter being in agreement with experiment. For the electric plasma frequency shift, a large quantitative difference is pointed out by the two approaches, although the frequency variation trend is similar. The fact that the scattered electric field is no longer polarized like the incident beam explains these differences, resulting in the unsuitability of an isotropic treatment of LC compounds infiltrated into metamaterials.

Experimental investigation of a metamaterial omnidirectional reflector

We demonstrate experimentally the existence of an omnidirectional reflection band of a two-dimensional metamaterial structure consisting of split ring resonators and thin conducting wires. Experimental angular reflectance data agree reasonably well with simulations using model dispersion relations for the effective dielectric permittivity and magnetic permeability that were fitted to the experimentally retrieved material parameters. The tunability of the reflection bandwidth is demonstrated by changing the effective electric plasma frequency. These findings are also relevant to optical frequencies where similar metamaterial composites have been fabricated.

Gap solitons in a nonlinear quadratic negative-index cavity

We predict the existence of gap solitons in a nonlinear, quadratic Fabry-Pérot negative index cavity. A peculiarity of a single negative index layer is that if magnetic and electric plasma frequencies are different it forms a photonic band structure similar to that of a multilayer stack composed of ordinary, positive index materials. This similarity also results in comparable field localization and enhancement properties that under appropriate conditions may be used to either dynamically shift the band edge, or for efficient energy conversion. We thus report that an intense, fundamental pump pulse is able to shift the band edge of a negative index cavity, and make it possible for a weak second harmonic pulse initially tuned inside the gap to be transmitted, giving rise to a gap soliton. The process is due to cascading, a well-known phenomenon that occurs far from phase matching conditions that limits energy conversion rates, it resembles a nonlinear third-order process, and causes pulse compression due to self-phase modulation. The symmetry of the equations of motion under the action of either an electric or a magnetic nonlinearity suggests that both nonlinear polarization and magnetization, or a combination of both, can lead to solitonlike pulses. More specifically, the antisymmetric localization properties of the electric and magnetic fields cause a nonlinear polarization to generate a dark soliton, while a nonlinear magnetization spawns a bright soliton.

Broadband omnidirectional reflection from negative index materials

We show, by using a dispersion relation with parameters taken from experimental data, that a single layer of a negative index material has omnidirectional reflection properties. In the range between the electric plasma frequency and the magnetic plasma frequency, the refractive index is close to zero and the negative index materials reflect radiation for all angles of incidence and polarization with reflectivities of ∼99%. In addition, with increasing angles of incidence, the reflecting band does not shift in frequency but actually widens. The operational bandwidth can be 100% or greater by increasing the separation between the electric and magnetic plasma frequencies.

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.