Nonlinear phenomena of left-handed nonlinear split-ring resonators

We theoretically analyze a two-dimensional periodic structure consisting of period nonlinear split-ring resonators (SRRs) with varactor diode. The diode is loaded into the slit of the SRRs. Then, we demonstrate nonlinear phenomena of left-handed nonlinear SRRs. This paper introduces nonlinear SRRs based on left-handed (LH) media and simulates self-tuning mechanisms, bistable effects in the microwave frequency range. In addition, with the increase of input power, the nonlinear response of the SRRs becomes multi-valued, paving a way for creating bistable tunable metamaterials.     

Narrow transmittance peaks in a multilayered microsphere with a quasiperiodic left-handed stack

We studied the photon spectrum in coated microspheres with alternating quasiperiodic layers having left-handed (LH) materials included. It is found that the band gap (spectral zone of nearly zero transmittancy) in such a system is strongly enhanced. At an increase of the quasiperiodicity parameter γ, the boundaries of the spectral band gaps acquire the intended shape. When γ exceeds the inverse golden mean value, a structure with extremely narrow separated resonant peaks with nearly complete transmittance arises. At increased γ, such resonances migrate to the center of the band gap. This effect allows creating optical filters with extremely narrow passbands.     

Extended verification of scaling behavior in split-ring resonators

We present an expanded LC-model for nanoscale split-ring resonators (SRR), including the influence of dielectric host materials. The LC-model is experimentally verified by changing the geometry of the SRR unit cell as well as by optofluidic tuning, where the SRR samples are covered with index oil. The extended model can be used as a general guideline for metal SRR structures with arbitrary dielectric host materials.     

Enhancement of sensitivity in optical waveguide sensors using left-handed materials

We show analytically that the sensitivity of an optical waveguide sensor can be dramatically enhanced by using a metamaterial with negative permittivity and permeability. The variation of the sensitivity of the proposed waveguide sensor with different parameters of the waveguide is studied. It is found that the sensitivity of the sensor increases with the increasing thickness of the metamaterial due to the surface polariton generation.     

The surface mode supported by an asymmetrical waveguide containing left-handed materials

The propagating characteristics of surface mode supported by an asymmetrical three-layer waveguide containing left-hand materials are studied in detail. The forward and the backward surface modes have been identified respectively through the slope of dispersion curve and the total energy flux of the structure. Research shows that anti-symmetry mode corresponds to forward surface wave. Furthermore, to symmetry mode, the type of surface mode depends on the distribution of the electric field in the left-handed layer. It is found that, the conversion between backward surface wave and forward surface wave is realizable by varying the thickness of the left-handed layer and the permittivity of the substrate.     

自由空间中左手材料传输特性的仿真研究

 研究了左手材料的传输和反射特性,介绍了所仿真的样品形式和测量系统,并采用高频构造仿真方法(HFSS)在已有自由空间宽频测量的基础上进行理论仿真。结果表明：S参量的数字仿真与实验测量结果在宽频条件下达到了较好的一致性;测量中产生的损耗主要归因于铜线结构有限的电导率;理论上左手材料的最佳无损工作频段应高于谐振环的谐振频率。     

Omni-reflectance and enhanced resonant tunneling from multilayers containing left-handed materials

We study the oblique transmission through a one-dimensional photonic crystal consisting of alternating slabs made of ordinary and negative refractive index materials, the latter being dispersive. We investigate the angular dependence of the band gap for this multilayer medium. Our results suggest, unlike a conventional Bragg gap, this type of gap exhibits a rather versatile behavior with varying angle of incidence. We find the angle-dependent characteristics for this type of gap can be quite different for different structural parameters of the constituents. Thus, multilayer structures involving left-handed components are very good candidates for band gap engineering. Specifically, we demonstrate for a certain experimentally realizable structure, the existence of a gap region for each individual polarization which survives for incident angles as high as 85 °. Moreover, we show how this structure can also function as a highly efficient polarization splitter. Finally, we investigate the multilayer medium when acting as single or double electromagnetic barrier. We study the tunneling properties of such systems for both types of individual barrier layers—right- and left-handed, respectively. We observe the double barrier exhibits resonant tunneling that depends on the “rightness” of the individual barrier layers.     

Expanding the bandwidth of planar MNG materials with co-directional split-ring resonators

An effective approach to expand the bandwidth of negative permeability of small-sized planar materials is proposed. Based on qualitative analysis of equivalent circuit models, the fractional bandwidth of an μ-negative (MNG) material is expanded from 3.53% up to 12.87% by adding split-ring resonators (SRRs) and arranging them by proposed steps. Moreover, the experimental results validate the effectiveness of bandwidth-expanding methods, which is promising for the extensive application of metamaterials in the microwave field.     

Theoretical study of left-handed behavior of composite metamaterials

We investigate numerically the transmission properties of 1D and 2D composite metamaterials (CMM) consisting of periodically arrangements of circular split-ring resonators (SRR) and wires. The theoretical methods used are the commercially available code Microwave Studio for transmission calculations and a retrieval procedure which gives the effective electric permittivity, , and magnetic permeability, μ, of the system. Our theoretical results are in good agreement with experimental data.     

Lamellar model of the left-handed metamaterials composed of metallic split-ring resonators and wires

Left-handed materials composed of split ring resonators (SRRs) and wires are investigated in the viewpoint of lamellar composite with epsilon-negative (ENG) and mu-negative (MNG) materials staked alternatively. Several configurations of the SRR-wire metamaterial are numerically simulated to confirm its left-handed response as an analogy to the ENG-MNG lamellar model.     

Strong tie between cut-wire pair and continuous wire in combined-structure metamaterials

A detail study on the continuity between cut-wire pair and continuous wire in combined-structure metamaterials operating at the microwave frequency regime is reported. By using numerical simulations and microwave experiments, we investigated the effect of the width and position of the continuous wire relative to the cut-wire pair on the electromagnetic response of a combined structure. It was found that these parameters play an important role in determining whether the left-handed (LH) behavior is obtained or not. In addition, we also studied the influence of lattice constant on the LH behavior of combined structure. Our results showed that the LH behavior is strongly dependent on the lattice constant in the E direction. However, it remains unchanged according to the lattice constant in the H direction. A good coincidence between the measurements and the numerical simulations was shown. It is expected that this work will allow us to optimize the appropriate characteristic parameters even without avoiding the trial-and-error fabrications.     

Identifying magnetic response of split-ring resonators at microwave frequencies

In this study we provide experimental methods to identify the magnetic resonance of split ring resonantors (SRR) at the microwave frequency regime. Transmission measurements were performed on both single SRR unit cell and periodic arrays of SRRs. The magnetic response of the SRR structure was demonstrated by comparing the transmission spectra of SRRs with closed ring resonators (CRR). Effects of the changes in the effective dielectric constant of the SRR medium on the band-gaps of SRR are investigated experimentally. SRRs not only exhibit a magnetic resonance band gap but also a band gap due to the electric resonance. Finally, we present the effect of electric coupling to the magnetic resonance of bianisotropic SRRs by utilizing SRRs with different orientations, and incident electromagnetic wave polarizations.     

Numerical analysis of propagation characteristics of electromagnetic wave in lossy left-handed material media

The propagation characteristics of electromagnetic wave in lossy left-handed materials (LHM) are studied using finite-difference time-domain (FDTD) method base on auxiliary differential equation (ADE) technology. The LHM medium is realized with lossy Drude models for both the negative electric permittivity and the negative magnetic permeability. The discretized ADE-FDTD equations are derived in detail. The incident wave used in the simulation is a multiple cycle m-n-m pulses source. The term of Poynting's vector E_xH_y was calculated. These numerical results demonstrate conclusively that the phase velocity direction of electromagnetic wave propagation and the direction of the Poynting vectors are anti-parallel in LHM. The amplitude of electric field is reduced with the enhancive distance of LHM slab. It is also demonstrated that the energy of electromagnetic wave in the LHM slab is obviously attenuated, and the attenuation of energy becomes stronger with the angular plasma frequency ω_p increasing. These results indicate that LHM stealth is effective in theory, and reasonable selection of the large negative index of refraction can greatly enhance its effectiveness.     

奇妙的左手材料

左手材料最早由前苏联科学家Veselago V G在20世纪60年代从理论上提出来的，是指一种介电常数g和磁导率μ同时为负值的材料．它具有诸如负群速度、负折射率、理想成像、逆Doppler频移、反常Cerenkov辐射等种种奇异的物理性质．经过多年的沉寂之后，近几年在实验上取得了突破性的进展，重新引起了人们的重视，尤其是在2003年，还被Science杂志评为当年十大科技进展之一．文章介绍了左手材料的概念和基本原理，并回顾了这一领域近年来的发展．     

左手性材料研究进展

综述了左手性材料的理论与实验研究方面取得的最新进展．采用电磁理论分析了左手性介质的基本性质；阐述了用左手性介质制作的平板透镜进行实现超衍射分辨率成像的机理；介绍了在人工构造左手性材料方面所取得的实验进展．     

Branching behavior of field dynamics of resonators of left-handed materials

In this paper, we study the spatiotemporal dynamics of left-handed materials that contain nonlinear cavities. These materials, having a negative refractive index, exhibit a nonlinear electromagnetic behavior. The insertion of the left-handed material into an optical cavity results into a variety of branching behavior of optical oscillators that are degenerate. The optical Kerr cavity considered in this work contains a cubic nonlinearity. The objective of this work was to investigate how branching behavior can yield useful information about the relative amount of left-handed and right-handed material controlling the diffraction in cavity. We will apply the reductive perturbation method-based multi-equation bifurcation theory to a scalar nonlinear Schrodinger equation and show how period-doubling occurs during optical wave propagation.     

GHz magnetic response of split ring resonators

Measurements of engineered subwavelength microstructures can be designed to have positive or negative and μ at desired frequencies. We present transmission measurements of a metamaterial consisting of split ring resonators (SRR). Results for different polarizations and propagation directions are presented. The transmission shows a dip even for propagations perpendicular to the SRR plane, provided that the incident electric field is parallel to the sides of the split ring resonators (SRRs) which contain the cuts. The experimental results agree well with the theoretical calculations.     

Unipolar photonic memristive-like nonlinear switching in split-ring resonator based metamaterials

Photonic memristor, which performs the function as memristor working on electromagnetic fields, can accelerate the development of all-optical network. A unipolar photonic memristive-like switching behavior in split-ring resonator based metamaterials was reported. Transmission-power (T-P) loops are observed in the metamaterials. And the T-P loops change with the detect frequency which indicates the tunability and designability of the photonic memristor. These behaviors are attributed to the increasing dielectric constant of MgTiO₃ ceramic caused by the interaction of sample and electromagnet field. The mechanism supplies a general foundation for photonic memristors which can be used from radio frequency to optical wavelength.     

Broadband planar left-handed metamaterials using split-ring resonator pairs

In this paper, we showed that split-ring resonator (SRR) pairs can be used as broadband planar left-handed metamaterials (LHMs). Simulations were carried out for one layer of infinite LHM slab using SRR pairs. The results showed that by carefully adjusting dimensions of the SRR pairs, magnetic and electric resonances can be coexistent at some frequency ranges and in the frequency range where there are both negative magnetic and electric responses, there is a broad LH band. Equivalent circuits for the magnetic and electric resonance were offered to give a qualitative and quantitative explanation of the LH behaviors of LHMs using SRR pairs.     

Towards some real applications for negative materials

The near field technologies, negative index materials (NIM), photonic crystals and plasmonics combined with innovation in high dielectric antennas, wireless systems, and photonic circuits open the prospect of novel antennas, integrated circuits, sensors (chemical, biological and individual molecule), medical scanners, displays and imagers, which have the potential to outperform conventional technology and create many commercial opportunities [A.J. Holden, Inside the Wavelength, Electromagnetics in the Near Field, State of the Science Review for DTI Foresight, UK, February 2004, available at: http://www.foresight.gov.uk/]. A selection of these applications is reviewed and the challenges for the technologies set in context.