Terahertz transmission properties of four metamaterials

We investigated the power transmission properties of four metamaterials in terahertz regime. The measured results reveal a global maximum transmission peak at 2.52 THz, and some local transmission peaks. In order to find a best metamaterials with relatively high transmission efficiency, we compared measured power transmission performances of four types of metamaterials microstructures, and analyzed their transmission differences.     

Photonic band gap and defect mode from a layered periodic structure with anisotropic nonmagnetic right-handed and left-handed metamaterials

We demonstrate a photonic band gap (PBG) from a layered periodic structure containing anisotropic nonmagnetic right-handed and left-handed metamaterials whose permittivity elements are partially negative. A set of criteria imposed on materials and structures to realize a PBG is derived, and the transmission spectra are also discussed. When a defect layer is introduced, some unusual properties are found in contrast to that of a defect mode in ordinary PBG structures.     

Double-negative dynamic properties in one-dimensional multi-phase metamaterial based on the symmetrical equivalent layer

Acoustic metamaterials have important potential applications in engineering by their unusual properties. Based on the concept of symmetrical equivalent layer, it is found that layered acoustic metamaterial which exhibits simultaneously negative effective modulus and density can be existed. By using the transfer matrix method, the continuous double-negative dynamic properties can be achieved through a multi-phase microstructure considering viscous damping, and the left-handed wave propagation property appears during the double-negative frequency regions. This will be a reference for the design of 1D acoustic negative refraction metamaterials.     

Experimental and numerical study of omega type bianisotropic metamaterials combined with a negative permittivity medium

We report on the transmission properties of the omega (Ω) type metamaterials. Transmission through the periodic Ω-only and Ω-wire metamaterials are studied experimentally and numerically. A resonance band gap is observed for the periodic Ω medium around the resonance frequency of the single Ω unit cell. A transmission band is observed below the resonance band gap, when the periodic Ω structure is embedded in a negative permittivity medium composed of thin metallic wire arrays. We also studied the effect of periodicity on the transmission spectra of Ω type metamaterials.     

Conversion from constitutive parameters to dispersive transmission line parameters for multi-band metamaterials

Abstract

In this study, we explain an approach including conversion from constitutive parameters to dispersive transmission line parameters using the double-band DNG (double-negative) properties of the circular type fishnet metamaterials. After designing the metamaterial structure, the numerical calculations and the composite right/left-handed (CRLH) modeling of circular-type metamaterials are realized in free space. Detailed dispersion characteristics give us the opportunity to explain the true behavior of the inclusions during the analysis stage. By combining the results coming from the standard retrieval procedure with the conventional CRLH theory, we calculate the actual values of the transmission line parameters for all frequency regimes. The constitutive parameters of an equivalent CRLH transmission line are derived and shown to be negative values. It is shown that the constitutive parameters present the same behavior for all negative refractive index regimes. The double-negative properties and the phase advance/lag behavior of metamaterials are observed based on the dispersive transmission line parameters.     

Tunable dual-band infrared chiral metamaterials based on double-layered asymmetric U-shape split ring resonators

We have numerically demonstrated chiral metamaterials based on double-layered asymmetric U-shape split ring resonators. Dual-band circular dichroism is found in the whole frequency regime from 50 to 250 THz by studying the transmission properties. Huge optical activity and the induced negative refractive index are obtained at resonance by calculating the optical activity and ellipticity of the transmitted E-fields. Chirality parameter and effective refractive index are retrieved to illustrate the tunable optical properties of the metamaterials. The underlying mechanisms for the observed circular dichroism are analyzed. These metamaterials would offer flexible electromagnetic applications in the infrared regime.     

Controlling light with plasmonic multilayers

Recent years have seen a new wave of interest in layered media – namely, plasmonic multilayers – in several emerging applications ranging from transparent metals to hyperbolic metamaterials. In this paper, we review the optical properties of such subwavelength metal–dielectric multilayered metamaterials and describe their use for light manipulation at the nanoscale. While demonstrating the recently emphasized hallmark effect of hyperbolic dispersion, we put special emphasis to the comparison between multilayered hyperbolic metamaterials and more broadly defined plasmonic-multilayer metamaterials A number of fundamental electromagnetic effects unique to the latter are identified and demonstrated. Examples include the evolution of isofrequency contour shape from elliptical to hyperbolic, all-angle negative refraction, and nonlocality-induced optical birefringence. Analysis of the underlying physical causes, which are spatial dispersion and optical nonlocality, is also reviewed. These recent results are extremely promising for a number of applications ranging from nanolithography to optical cloaking.     

Theoretical investigation of the sound attenuation of membrane-type acoustic metamaterials

Membrane-type acoustic metamaterials have been recently shown to exhibit good performance of sound attenuation in a low frequency range. An analytical approach for the fast calculation of sound transmission loss of the membrane-type acoustic metamaterials is presented here. The discussion indicate that the first transmission loss valley and the transmission loss peak depend strongly on the attaching mass, while the second transmission loss valley is mainly influenced by the membrane properties. The effects of membrane tension and mass position on the transmission loss and characteristic frequencies are also discussed in detail.     

基于谐振结构的左右手传输线的奇异传输性质

通过对一种具有谐振结构的左右手传输线进行了数值仿真和分析，从有效磁导率和介电常数及色散关系来说明其奇异的传输特性.把这种左右手传输线用作漏波天线并测量了在不同频率点的方向图，从而实验上验证了这种特殊结构在不同的频率范围内可以实现一个左手性通带，也可以实现两个左手性通带.对这种结构传输特性的研究，有助于其在漏波天线方面的应用.     

Wide-band tuneability,nonlinear transmission,and dynamic multistability in SQUID metamaterials

Superconducting metamaterials comprising rf Superconducting QUantum Interference Devices (SQUIDs) have been recently realized and investigated with respect to their tuneability, permeability, and dynamic multistability properties. These properties are a consequence of intrinsic nonlinearities due to the sensitivity of the superconducting state to external stimuli. SQUIDs, made of a superconducting ring interrupted by a Josephson junction, possess yet another source of nonlinearity, which makes them widely tuneable with an applied dc dlux. A model SQUID metamaterial, based on electric equivalent circuits, is used in the weak coupling approximation to demonstrate the dc flux tuneability, dynamic multistability, and nonlinear transmission in SQUID metamaterials comprising non-hysteretic SQUIDs. The model equations reproduce the experimentally observed tuneability patterns and predict tuneability with the power of an applied ac magnetic field. Moreover, the results indicate the opening of nonlinear frequency bands for energy transmission through SQUID metamaterials, for sufficiently strong ac fields.     

Metamaterials and metasurfaces for designing metadevices:Perfect absorbers and microstrip patch antennas

In the past twenty years, electromagnetic metamaterials represented by left-handed metamaterials(LHMs) have attracted considerable attention due to the unique properties such as negative refraction, perfect lens, and electromagnetic cloaks. In this paper, we present a comprehensive review of our group's work on metamaterials and metasurfaces. We present several types of LHMs and chiral metamaterials. As a two-dimensional equivalent of bulk three-dimensional metamaterials, metasurfaces have led to a myriad of devices due to the advantages of lower profile, lower losses, and simpler to fabricate than bulk three-dimensional metamaterials. We demonstrate the novel microwave metadevices based on metamaterials and metasurfaces: perfect absorbers and microwave patch antennas, including novel transmission line antennas,high gain resonant cavity antennas, wide scanning phased array antennas, and circularly polarized antennas.     

Plasmon analysis and homogenization in plane layered photonic crystals and hyperbolic metamaterials

Dispersion equations are obtained and analysis and homogenization are carried out in periodic and quasiperiodic plane layered structures consisting of alternating dielectric layers, metal and dielectric layers, as well as graphene sheets and dielectric (SiO₂) layers. Situations are considered when these structures acquire the properties of hyperbolic metamaterials (HMMs), i.e., materials the real parts of whose effective permittivity tensor have opposite signs. It is shown that the application of solely dielectric layers is more promising in the context of reducing losses.     

Anomalous reflection and excitation of surface waves in metamaterials

We consider reflection of electromagnetic waves from layered structures with various dielectric and magnetic properties, including metamaterials. Assuming periodic variations in the permittivity, we find that the reflection is in general anomalous. In particular, we note that the specular reflection vanishes and that the incident energy is totally reflected in the backward direction, when the conditions for resonant excitation of leaking surface waves are fulfilled.     

Engineering the point spread function of layered metamaterials

Layered metal-dielectric metamaterials have filtering properties both in the frequency domain and in the spatial frequency domain. Engineering their spatial filtering response is a way of designing structures with specific diffraction properties for such applications as sub-diffraction imaging, supercollimation, or optical signal processing at the nanoscale. In this paper we review the recent progress in this field. We also present a numerical optimization framework for layered metamaterials, based on the use of evolutionary algorithms. A measure of similarity obtained using Hölder’s inequality is adapted to construct the overall criterion function. We analyse the influence of surface roughness on the quality of imaging.     

Parallel laser microfabrication of terahertz metamaterials and its polarization-dependent transmission property

Large-area split ring resonator (SRR) array was fabricated by femtosecond laser micro-lens array lithography at a fast speed. Transmission spectra of the SRR arrays at different incident terahertz wave polarization states were characterized by terahertz time domain spectroscopy. A polarization-dependent transmission property of the SRR array was observed. Polarization-dependent loss (PDL) spectrum was characterized to investigate the polarization properties of the terahertz metamaterials. The PDL characterization can eliminate the substrate effect and provide a flexible platform to study the characteristics of free-standing terahertz metamaterials.     

Effect of metal permittivity on resonant properties of terahertz metamaterials

We investigate the effect of metal permittivity on resonant transmission of metamaterials by terahertz time-domain spectroscopy. Our experimental results on double split-ring resonators made from different metals confirm the recent numerical simulations [Phys. Rev. E 65, 036622 (2002)] that metamaterials exhibit permittivity-dependent resonant properties. In the terahertz regime, the measured inductive-capacitive resonance is found to strengthen with a higher ratio of the real to the imaginary parts of metal permittivity, and this remains consistent at various metal thicknesses. Furthermore, we found that metamaterials made even from a generally poor metal become highly resonant owing to a drastic increase in the value of the permittivity at terahertz frequencies.     

Effect of metamaterial layer on optical surface plasmon resonance sensor

In this paper an optical surface plasmon resonance (SPR) sensor with metamaterial for four and five layered structure is studied. The numerical results presented in this paper leads to a significant properties of metamaterials in sensing field. Computed results of SPR sensors using metamaterial are compared with conventional optical SPR sensors for four and five layered structure. It is seen that wider dynamic range or effective range of measurable refractive index increases when metamaterial layer is used. It is also verified that SPR sensor with metamaterial layer can dramatically enhance the resolution and reduce the reflectivity compared with conventional SPR. Validity of the magnetic field results is proved on the basis of smooth match of the fields in the different layers of the proposed optical SPR sensor.     

Collision enhanced hyper-damping in nonlinear elastic metamaterial

Nonlinear elastic metamaterial, a topic which has attracted extensive attention in recent years, can enable broadband vibration reduction under relatively large amplitude. The combination of damping and strong nonlinearity in metamaterials may entail extraordinary effects and offer the capability for low-frequency and broadband vibration reduction. However, there exists a clear lack of proper design methods as well as the deficiency in understanding properties arising from this concept. To tackle this problem, this paper numerically demonstrates that the nonlinear elastic metamaterials, consisting of sandwich damping layers and collision resonators, can generate very robust hyper-damping effect, conducive to efficient and broadband vibration suppression. The collision-enhanced hyper damping is persistently presented in a large parameter space, ranging from small to large amplitudes, and for small and large damping coefficients. The achieved robust effects greatly enlarge the application scope of nonlinear metamaterials. We report the design concept, properties and mechanisms of the hyper-damping and its effect on vibration transmission. This paper reveals new properties offered by nonlinear elastic metamaterials, and offers a robust method for achieving efficient low-frequency and broadband vibration suppression.     

Absorption and dispersion in metamaterials: Feasibility of device applications

We present a quantitative study of the effects of losses in layered media with a metamaterial layer as the constituent. The metamaterial is modelled by a causal isotropic effective medium (Lorentz-type) response. The parameters for the model are picked from a recent experiment. Two specific examples, namely, that of resonant tunnelling (RT) and imaging are chosen to demonstrate the devastating effects of losses in the present day metamaterials. It is then shown how large delays in RT, as well as near perfect imaging can be restored in gain-doped metamaterials. We also point out yet another use of metamaterials for achieving near perfect absorption, and its use for probing strong atom-field interaction.