Array Of Split-ring Resonators Research Articles

Reflective metamaterial polarization converter in a broad frequency range

We propose a broadband reflective metamaterial polarization converter which is composed of arrays of split-ring resonators (SRRs), a dielectric layer and a continuous metallic layer. For the case of a loss-free dielectric layer, the average transformation rate is around 90% at frequencies from 6.68 to 10.91 GHz, and the bandwidth is 56.66% of the central wavelength. The increased loss tangent of the dielectric layer is shown to induce a reduced transformation rate due to enhanced absorption.

Electro-optic tuning of split ring resonators embedded in a liquid crystal

Two-dimensional arrays of split ring resonators for near-infrared frequencies are embedded in a liquid crystal (LC) and the influences of LC alignment, temperature, and electric fields on the resonance frequencies are studied. The results show that tunability can not only be achieved by influencing the state of polarization of the incident radiation, but also by direct interaction of the evanescent field of the resonant modes with the LC. Depending on the LC alignment, the field-induced shift of the resonance frequency is found to vary for different excited modes. Some guidelines for the design of tunable frequency selective metasurfaces can be deduced from these experimental results.

Fanolike resonance in light transmission through a silver film perforated with an array of SRR-shaped apertures

We study theoretically light transmission through a silver film perforated with an array of split-ring resonator (SRR) shaped apertures. An asymmetric lineshape, which is characteristic of the Fano resonance, has been found in a narrow frequency range of the spectrum. The effect can be attributed to the interference between propagating surface plasmon polaritons (SPPs) on the silver film and magnetic plasmon polaritons (MPPs) associated with the SRR-shaped apertures. An anticrossing behavior of the resonance positions has also been observed in the transmission spectra, demonstrating the strong coupling of the SPPs with the MPPs. Due to the steep dispersion of the Fano resonance profile, the plasmonic nanostructure proposed could find important applications in sensors, switching, and nonlinear and slow-light devices.

An experimental verification of metamaterial coupled enhanced transmission for antenna applications

Inspired by the work of Bethe on electromagnetic transmission through subwavelength hole, there has been immense interest on the extraordinary transmission through subwavelength slot/slit on metal plates. The invention of metamaterials has boosted the extra ordinary transmission through subwavelength slots. We examine computationally and experimentally the concept of metamaterial cover using an array of split ring resonators (SRRs), for enhancing the transmission in a stacked dipole antenna working in the S band. The front to back ratio is considerably improved by enhancing the magnetic resonant strength in close proximity of the slit of the upper parasitic dipole. The effect of stacking height of the SRR monolayer on the resonant characteristics of the split ring resonators and its effect on antenna radiation characteristics has been studied.

Molecular Split-Ring Resonators Based on Metal String Complexes

Metal string complexes or extended metal atom chains (EMACs) belong to a family of molecules that consist of a linear chain of directly bonded metal atoms embraced helically by four multidentate organic ligands. These four organic ligands are usually made up of repeating pyridyl units, single-nitrogen-substituted heterocyclic annulenes, bridged by independent amido groups. Here, in this paper, we show that these heterocyclic annulenes are actually nanoscale molecular split-ring resonators (SRRs) that can exhibit simultaneous negative electric permittivity and magnetic permeability in the UV-Vis region. Moreover, a monolayer of self-assembled EMACs is a periodic array of molecular SRRs which can be considered as a negative refractive index material. In the molecular scale, where the quantum-size effect is significant, we apply the tight-binding method to obtain the frequency-dependent permittivity and permeability of these molecular SRRs with their tensorial properties carefully considered.

Frequency tunable terahertz filter based on dual layered split-ring resonator array

Terahertz frequency tunable filter based on the dual layered split-ring resonator (SRR) array was fabricated on flexible polyimide film using conventional photolithography techniques. The fabricated SRR array was measured by terahertz time-domain spectroscopy (THz-TDS) and compared with the simulation data. We found that the center frequency could be controlled from 1.04 to 1.65 THz by the dipole coupling effect between upper and lower SRR layers. The bandwidth of the fabricated filter is also confirmed to be tuned validly ranging from 1.04 to 1.72 THz. By using the extracted field distribution, we verified that the localized field enhancement could be manipulated by changing the coupling distance between adjacent layers.

Effect of Alignment on a Liquid Crystal/Split‐Ring Resonator Metasurface

A metasurface comprising a two-dimensional array of split-ring resonators with resonance frequencies in the near-infrared region is fabricated and embedded in a uniformly aligned liquid crystal. The change of the dielectric permittivity in proximity to the plasmonic structure by the replacement of air with the liquid crystal results in a decrease in resonance frequencies. The resonance shift can be attributed to the interaction of the evanescent field of the excited resonant plasmon modes with the liquid crystal. This shift in resonance frequency is found to depend on the liquid-crystal alignment and to vary for different modes. Also, the resulting effects of changes in temperature or applied external electric field on the metasurface depend on the liquid-crystal alignment and may differ from mode to mode. These observations indicate that the characteristic frequencies of the resonant split-ring resonator modes may depend on different evanescent field components interacting with the liquid crystal. Consequently, certain design rules should be taken into account for the development of tunable metasurfaces based on liquid crystals.

Complementary chiral metasurface with strong broadband optical activity and enhanced transmission

We present the design and realization of ultra-thin chiral metasurfaces with giant broadband optical activity in the infrared wavelength. The chiral metasurfaces consisting of periodic hole arrays of complementary asymmetric split ring resonators are fabricated by femtosecond laser two-photon polymerization. Enhanced transmission with strong polarization conversion up to 97% is observed owing to the chiral surface plasmons resulting from mirror symmetry broken. The dependence of optical activity on the degree of structural asymmetry is investigated. This simple planar metasurface is expected to be useful for designing ultra-thin active devices and tailoring the polarization behavior of complex metallic nanostructures.

Tuning of resonance frequency in array of split-ring resonators in terahertz range

A numerical investigation of individual symmetric and asymmetric SRRs and planar arrays of SRRs is performed using the finite-difference time-domain method. The types of current resonances in such structures are determined. The relevance between the band-stop filtering effect in pulse transmission and the current resonances within the SRR is identified. Dependence of the resonant frequency on the size of the SRR is established. The tuning of the resonance frequency of the varactor-loaded SRR array is carried out by changing the depletion capacitance of the Schottky barrier.

Tuning of resonance frequency in array of split-ring resonators in terahertz range

A numerical investigation of individual symmetric and asymmetric SRRs and planar arrays of SRRs is performed using the finite-difference time-domain method. The types of current resonances in such structures are determined. The relevance between the band-stop filtering effect in pulse transmission and the current resonances within the SRR is identified. Dependence of the resonant frequency on the size of the SRR is established. The tuning of the resonance frequency of the varactor-loaded SRR array is carried out by changing the depletion capacitance of the Schottky barrier.

Design of high-gain broadband low-RCS waveguide slot antenna

A novel design for high gain and low radar cross section (RCS) waveguide slot antenna is proposed. Low RCS screen composed of orthogonal array of complementary split ring resonator etched square patch artificial magnetic conductor (CSRR-AMC) is exploited on the antenna for radiation improvement and broadband RCS reduction. Measured results demonstrate that the operating bandwidth is increased by 100 MHz and the gain is enhanced by 3.2 dB with the proposed structure. Meanwhile, 10 dB RCS reduction is achieved over the range of 5.52–6.63 GHz, implying 20% relative bandwidth.

Symplectic FDTD algorithm for the simulations of double dispersive materials

Combined with the Lossy Drude-Lorentz dispersive model, a symplectic finite-difference time-domain (SFDTD) algorithm is proposed to deal with the double dispersive model. Based on matrix splitting, symplectic integrator propagator and the auxiliary differential equation (ADE) technique, with the rigorous and artful formula derivation, the algorithm is constructed, and detailed formulations are provided. Excellent agreement is achieved between the SFDTD-calculated and exact theoretical results when transmittance coefficient in simulation of double dispersive film in one dimension is calculated. As to numerical results for a more realistic structure in three dimensions, the simulation of periodic arrays of silver split-ring resonators using the Drude dispersion model are also included. The transmittance, reflectance, and absorptance of the structure are presented to test the efficiency of the proposed method. Our method can be used as an efficiency simulation tool for checking the experimental data.

Optimization of Modulation Properties of Terahertz Metamaterial by Tuning Fabry–Pérot Resonances

In this work, we investigate the transmission properties of planar arrays of split-ring resonators formed on the surface of a dielectric plate. The modulation concept is demonstrated by using several metamaterial structures with a different effective capacitance of the split gap, thus imitating a metamaterial of tunable frequency. The proposed modulation scheme can be employed in the fabrication of a fast narrow-band terahertz modulator. The influence of Fabry–Perot resonances in the dielectric substrate on the parameters of the possible metamaterial-based modulator is analyzed in the terahertz region. Our results demonstrate that tuning the dielectric plate parameters allows for the optimization of the modulator performance. The presented modulation scheme based on frequency-tunable metamaterial offers a high modulation depth (95% at 425 GHz) with the resonant frequency tuning as small as ${\sim} 15\hbox{\%}$ . Measurement results are found in agreement with calculations.

Second-Order Nonlinearity in Triangular Lattice Perforated Gold Film due to Surface Plasmas Resonance

We have studied the excitation second-order nonlinearity through a triangular lattice perforated gold film instead of square lattice in many papers. Under the excitation of surface plasmas resonance effect, the second order nonlinearity exists in the noncentrosymmetric split-ring resonators arrays. Reflection of fundamental frequency wave through a triangular lattice perforated gold film is obtained. We also described the second harmonic conversion efficiencies in the second order nonlinear optical process with the spectra. Moreover, the electric field distributions of fundamental frequency above the gold film region are calculated. The light propagation through the holes results in the enhancement of the second order nonlinearity including second harmonic generation as well as the sum (difference) frequency generation.

Multiband meandered miniaturized patch antenna loaded with split ring resonator and thin wire arrays

ABSTRACTArtificial materials have attracted considerable attention as potential solutions to meet the demands of modern microwave technology for simultaneously achieving component minimization and higher performance in wireless communications, mobile communications, and satellite communication applications. So in this letter, we have investigated a multiband meandered miniaturized patch antenna with the use of split ring resonator (SRR) and thin wire arrays. SRR are promising building blocks for negative permeability metamaterials and thin wire arrays for negative permittivity. By combining SRR arrays and wire arrays together, we observed a transmission band where both permittivity and permeability are simultaneously negative. Simulated results for the S11 and electric field of an antenna are presented. The result shows multibands centered at 1.89, 2.04, 2.13, and 2.31 GHz. Design results are obtained by a high frequency structure simulator which is used for simulating microwave passive components. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:306–310, 2014

A symplectic FDTD algorithm for the simulations of lossy dispersive materials

A high-order symplectic finite-difference time-domain (SFDTD) algorithm, based on the matrix splitting, the symplectic integrator propagator and the auxiliary differential equation (ADE) technique, is presented. The algorithm is applied to the lossy Lorentz–Drude dispersive model. With the rigorous and artful formula derivation, the detailed formulations are provided. Moreover, the present algorithm can also be applicable to the lossy Drude and Lorentz dispersive model in a straightforward manner. An excellent agreement is achieved between the SFDTD-calculated and exact theoretical results when calculating the transmission coefficient in simulation of metal films. Focusing action of the matched left-handed materials (LHMs) slab is also achieved as the second example in the two-dimensional space. Numerical results for a more realistic structure, the simulation of periodic arrays of silver split-ring resonators (SRRs) using the Drude dispersion model, are also included, and the results agree well with those obtained by the finite element method (FEM).

Electrically small resonators for energy harvesting in the infrared regime

A novel structure based on electrically small resonators is proposed for harvesting the infrared energy and yielding more than 80% harvesting efficiency. The dispersion effect of the dielectric and conductor materials of the resonators is taken into account by applying the Drude model. A new scheme to channel the infrared waves from an array of split ring resonators is proposed, whereby a wide-bandwidth collector is utilized by employing this new channeling concept.

Optical properties of two-dimensional magnetoelectric point scattering lattices

We explore the electrodynamic coupling between a plane wave and an infinite two-dimensional periodic lattice of magneto-electric point scatterers, deriving a semi-analytical theory with consistent treatment of radiation damping, retardation, and energy conservation. We apply the theory to arrays of split ring resonators and provide a quantitive comparison of measured and calculated transmission spectra at normal incidence as a function of lattice density, showing excellent agreement. We further show angle-dependent transmission calculations for circularly polarized light and compare with the angle-dependent response of a single split ring resonator, revealing the importance of cross coupling between electric dipoles and magnetic dipoles for quantifying the pseudochiral response under oblique incidence of split ring lattices.

Mechanism of optical terahertz-transmission modulation in an organic/inorganic semiconductor interface and its application to active metamaterials

Terahertz (THz) transmission modulation through copper phthalocyanine (CuPc)-coated Si under various laser light irradiation conditions was investigated using THz time-domain spectroscopy. The charge carrier transfer from Si to CuPc is crucial for photo-induced metallization, and the thickness of the CuPc layer is a critical parameter for achieving high charge carrier density for metallization. Transmission through a split-ring resonator array metamaterial, fabricated on CuPc-coated Si, can be efficiently modulated by laser light irradiation. Our findings may open the way for various types of metamaterials using organic conjugated materials that are suitable for easy device fabrication using printing technologies.

Near Field Coupling in Passive and Active Terahertz Metamaterial Devices

A wide variety of optical phenomena rely on the near field manipulation and confinement of electromagnetic field in subwavelength metallic and dielectric resonators with applications ranging from the design of micro and nano scale photonic devices to super lenses and ultrasensitive sensors. In this invited paper, we present a discussion on controlling the metamaterial properties by active and passive manipulation of near field coupling in an array of split ring resonators. We show that near field coupling between the meta-atoms could lead to resonance tuning, mode splitting, and ultrafast switching in passive and active resonators. The near field coupling schemes discussed here demonstrate the application possibilities of such structures towards the design of active switches, amplitude modulators, frequency agile behaviors, and slow light devices, particularly for the terahertz frequency regime, which still suffers from the shortage of practical devices required to bridge the so called “THz gap”.