Metamaterial Split Ring Resonator Research Articles

Optically switchable and tunable terahertz metamaterials through photoconductivity

We present both theoretical and experimental cases for realizing optically switchable and tunable split-ring resonator (SRR) metamaterials operating in the THz regime. This is achieved by suitably placing photoconducting semiconductors in the various SRR designs. Exciting the semiconductor by an optical pump beam, the realization of single- and multi-band switching, blue-shift and red-shift tunability, and broad-band phase modulation are demonstrated.

Terahertz Response of Metamaterial Split-Ring Resonators: Numerical Analysis and Topology Design

Using numerical simulation techniques, the response characteristics of metamaterials split-ring resonators (SRRs) in terahertz region are analyzed. We examine the transmission and dispersion characteristics of several SRRs and show that there are two significant resonances corresponding to electric response and magnetic response, respectively. Based on the topology optimization technique, a terahertz magnetic response of metamaterial for the goal of maximum bandwidth is performed, the results seem to imply that the SRRs structure is the most reasonable topological form for broad magnetic resonance in THz band.

Electric toroidal dipole response in split-ring resonator metamaterials

Toroidal dipoles are usually masked by other stronger effects of classical electric and magnetic multipoles, such as dipoles, quadrupoles, octupoles and so forth. So observation of the toroidal response is extremely rare. For the first time we present an electric toroidal dipole model based on metamaterials, which is composed of split-ring resonators. The transmission and reflection spectra show that there are two resonances at the frequency of 5.0 GHz and 11.2 GHz. Calculated radiated power dispersion for various multipole moments derived from the current density proved that these two resonances are electric dipole response and elusive electric toroidal dipole response respectively. Our experimental evidence of electric toroidal dipole response brings attentions to the often ignored toroidal multipoles.

Distinguishing octane grades in gasoline using terahertz metamaterials

Distinguishing octane numbers of commercial gasoline is experimentally demonstrated by use of single split-ring resonator metamaterials functioning at terahertz frequencies. The differences in frequency-dependent absorption coefficients and refractive indices of various grades of gasoline lead to a modification in the surrounding dielectric environment and consequently the resonance properties of the planar metamaterials. This consequently enables a distinct frequency shift in the inductive-capacitive electric dipolar resonances. This paper reveals that such metamaterial arrays, as highly sensitive chemical sensors, have promising potential in petroleum industrial applications.

Electromagnetic energy within coated spheres containing dispersive metamaterials

An exact expression is derived for the time-averaged electromagnetic energy within a magneto-dielectric coated sphere, which is irradiated by a plane and time-harmonic electromagnetic wave. Both the spherical shell and core are considered to be dispersive and lossy, with a realistic dispersion relation of an isotropic split-ring resonator metamaterial. We obtain analytical expressions for the stored electromagnetic energies inside the core and the shell separately and calculate their contributions to the total average energy density. The stored electromagnetic energy is calculated for two situations involving a metamaterial coated sphere: a dielectric shell and dispersive metamaterial core, and vice versa. An explicit relation between the stored energy and the optical absorption efficiency is also obtained. We show that the stored electromagnetic energy is an observable sensitive to field interferences responsible for the Fano effect. This result, together with the fact that the Fano effect is more likely to occur in metamaterials with negative refraction, suggest that our findings may be explored in applications.

THz near-field Faraday imaging in hybrid metamaterials

We report on direct measurements of the magnetic near-field of metamaterial split ring resonators at terahertz frequencies using a magnetic field sensitive material. Specifically, planar split ring resonators are fabricated on a single magneto-optically active terbium gallium garnet crystal. Normally incident terahertz radiation couples to the resonator inducing a magnetic dipole oscillating perpendicular to the crystal surface. Faraday rotation of the polarisation of a near-infrared probe beam directly measures the magnetic near-field with 100 femtosecond temporal resolution and (λ/200) spatial resolution. Numerical simulations suggest that the magnetic field can be enhanced in the plane of the resonator by as much as a factor of 200 compared to the incident field strength. Our results provide a route towards hybrid devices for dynamic magneto-active control of light such as isolators, and highlight the utility of split ring resonators as compact probes of magnetic phenomena in condensed matter.

Ultrastrong Coupling of the Cyclotron Transition of a 2D Electron Gas to a THz Metamaterial

Artificial cavity photon resonators with ultrastrong light-matter interactions are attracting interest both in semiconductor and superconducting systems because of the possibility of manipulating the cavity quantum electrodynamic ground state with controllable physical properties. We report here experiments showing ultrastrong light-matter coupling in a terahertz (THz) metamaterial where the cyclotron transition of a high-mobility two-dimensional electron gas (2DEG) is coupled to the photonic modes of an array of electronic split-ring resonators. We observe a normalized coupling ratio, Ω/ω(c) = 0.58, between the vacuum Rabi frequency, Ω, and the cyclotron frequency, ω(c). Our system appears to be scalable in frequency and could be brought to the microwave spectral range with the potential of strongly controlling the magnetotransport properties of a high-mobility 2DEG.

Magnetic response of split ring resonator metamaterials: From effective medium dispersion to photonic band gaps

On systematically investigating the electromagnetic response of periodic split-ring resonator (SRR) metamaterials as a function of the size-to-wavelength (a/λ) ratio, we find that the stop bands due to the geometric resonances of the SRR weaken with increasing (a/λ) ratio, and are eventually replaced by stop bands due to Bragg scattering. Our study traces the behaviour of SRR-based metamaterials as the resonance frequency increases and the wavelength of the radiation finally becomes comparable to the size of the unit cell of the metamaterial. In the intermediate stages, the dispersion of the SRR metamaterial can still be described as due to a localized magnetic resonances while Bragg scattering finally becomes the dominant phenomenon as a/λ∼1/2.

WIDEBAND NEGATIVE PERMITTIVITY METAMATERIAL FOR SIZE REDUCTION OF STOPBAND FILTER IN ANTENNA APPLICATIONS

The design and simplifled analysis of a compact and wide band (16%) negative permittivity complementary split ring resonator metamaterial is introduced. The proposed metamaterial component was applied to reduce the size of the feeding line fllter of microstrip patch antenna for the sake of higher order harmonic suppression. The reduction has been done using only one element of complementary split ring resonator, while maintaining the antenna's performance. Simplifled theoretical study and design of the proposed circuits has been presented. Moreover, experimental results have been done for validation and conformation purpose. Results conflrm that almost 95% of the antenna noise harmonics power has been removed.

A metamaterial inspired miniaturized phi-shaped high gain antenna for skin cancer detection

This paper introduces a new low cost, robust miniaturized micro strip high gain antenna inspired with metamaterial split ring resonator structure (SRR). Because of metamaterials property, there has been considerable reduction in size. The overall antenna structure is phi shaped which is equivalently two SRRs placed back to back. This miniaturized phi shaped antenna (MPSA) thus obtained, has been simulated on EM solver Ansoft HFSS and scattering matrix parameters are analyzed. Excellent performance in terms size, gain and radiation pattern is achieved. These types of antennas are very useful for applications where space of equipment is a constraint like microwave detection of skin cancer. Key words: Metamaterial, split ring resonator, microwave, microstrip structures, miniaturized antennas.

Maskless multiple-beam laser lithography for large-area nanostructure/microstructure fabrication

This paper reports a maskless multiple-beam laser lithography technique for large-area nanostructure/microstructure fabrication. This lithography technique can flexibly generate arbitrary nanostructures/microstructures over a large area at a high speed. The feature size of the nanostructures/microstructures can be controlled by exposure time and moving speed of the nanostage. Functional predesigned patterns, including split-ring resonator metamaterials for terahertz waves, can be obtained. More complicated structures can be made by single- and double-exposure schemes to make hybrid nanostructures/microstructures and tune surface plasmonic resonance properties. Meanwhile, microstructures with large height to lateral dimension ratios (2.5D microstructures) fabricated on silicon substrates can be used as mold tools for soft lithography. This technology shows its unique capacity to create various nanostructures/microstructures for extensive applications.

Hybridization Induced Transparency in composites of metamaterials and atomic media

We report hybridization induced transparency (HIT) in a composite medium consisting of a metamaterial and a dielectric. We develop an analytic model that explains HIT by coherent coupling between the hybridized local fields of the metamaterial and the dielectric or an atomic system in general. In a proof-of-principle experiment, we evidence HIT in a split ring resonator metamaterial that is coupled to α-lactose monohydrate. Both, the analytic model and numerical calculations confirm and explain the experimental observations. HIT can be considered as a hybrid analogue to electromagnetically induced transparency (EIT) and plasmon-induced transparency (PIT).

Electric and magnetic dipole couplings in split ring resonator metamaterials

In this paper, the electric and the magnetic dipole couplings between the outer and the inner rings of a single split ring resonator (SRR) are investigated. We numerically demonstrate that the magnetic resonance frequency can be substantially modified by changing the couplings of the electric and magnetic dipoles, and give a theoretical expression of the magnetic resonance frequency. The results in this work are expected to be conducive to a deeper understanding of the SRR and other similar metamaterials, and provide new guidance for complex metamaterials design with a tailored electromagnetic response.

A metamaterials inspired miniaturized phi-shaped antenna

This paper introduces a new low cost, robust miniaturized microstrip antenna inspired with metamaterial split ring resonator structure (SRR). Because of metamaterials property there has been considerable reduction in size. The overall antenna structure is phi shaped which is equivalent to two SRRs placed back to back. This phi shaped antenna (PSA) thus obtained has been simulated on EM solver Ansoft HFSS and scattering matrix parameters are analysed. Excellent performance in terms of size and radiation pattern is achieved. These types of antennas are very useful for applications where space of equipment is a constraint. Key words: Metamaterial, split ring resonator, microwave, microstrip structures, miniaturized antennas.

Flexible Visible–Infrared Metamaterials and Their Applications in Highly Sensitive Chemical and Biological Sensing

Flexible electronic and photonic devices have been demonstrated in the past decade, with significant promise in low-cost, light-weighted, transparent, biocompatible, and portable devices for a wide range of applications. Herein, we demonstrate a flexible metamaterial (Metaflex)-based photonic device operating in the visible-IR regime, which shows potential applications in high sensitivity strain, biological and chemical sensing. The metamaterial structure, consisting of split ring resonators (SRRs) of 30 nm thick Au or Ag, has been fabricated on poly(ethylene naphthalate) substrates with the least line width of ∼30 nm by electron beam lithography. The absorption resonances can be tuned from middle IR to visible range. The Ag U-shaped SRRs metamaterials exhibit an electric resonance of ∼542 nm and a magnetic resonance of ∼756 nm. Both the electric and magnetic resonance modes show highly sensitive responses to out-of-plane bending strain, surrounding dielectric media, and surface chemical environment. Due to the electric and magnetic field coupling, the magnetic response gives a sensitivity as high as 436 nm/RIU. Our Metaflex devices show superior responses with a shift of magnetic resonance of 4.5 nm/nM for nonspecific bovine serum albumin protein binding and 65 nm for a self-assembled monolayer of 2-naphthalenethiol, respectively, suggesting considerable promise in flexible and transparent photonic devices for chemical and biological sensing.

Tailored resonator coupling for modifying the terahertz metamaterial response

We experimentally and numerically study the nature of coupling between laterally paired terahertz metamaterial split-ring resonators. Coupling is shown to modify the inductive-capacitive (LC) resonances resulting in either red or blue-shifting. Results indicate that tuning of the electric and magnetic coupling parameters may be accomplished not by changing the orientation or density of SRRs, but by a design modification at the unit cell level. These experiments illustrate additional degrees of freedom in tuning the electromagnetic response, which offers a path to more robust metamaterial designs.

Strong Coupling between Nanoscale Metamaterials and Phonons

We use split ring resonators (SRRs) at optical frequencies to study strong coupling between planar metamaterials and phonon vibrations in nanometer-scale dielectric layers. A series of SRR metamaterials were fabricated on a semiconductor wafer with a thin intervening SiO(2) dielectric layer. The dimensions of the SRRs were varied to tune the fundamental metamaterial resonance across the infrared (IR) active phonon band of SiO(2) at 130 meV (31 THz). Strong anticrossing of these resonances was observed, indicative of strong coupling between metamaterial and phonon excitations. This coupling is very general and can occur with any electrically polarizable resonance including phonon vibrations in other thin film materials and semiconductor band-to-band transitions in the near to far IR. These effects may be exploited to reduce loss and to create unique spectral features that are not possible with metamaterials alone.

Bandwidth Enhancement and Size Reduction of Microstrip Patch Antenna by Magnetoinductive Waveguide Loading

A planar magnetoinductive (MI) waveguide loaded rectangular microstrip patch antenna is presented and discussed. The MI waveguide consists of two planar metamaterial split squared ring resonators (SSRRs) placed in between two microstrip lines. The backward wave propagation takes place through this structure. The rectangular microstrip patch antenna is magnetically coupled to the MI waveguide. The unloaded rectangular microstrip patch antenna resonates at 37.10 GHz. When loaded with planar MI waveguide, its resonant frequency is reduced to 9.38 GHz with the bandwidth and gain of 44% and 4.16 dBi respectively. In loaded condition, the dimension of antenna is 12.50 mm × 3.70 mm (0.390 λ × 0.115 λ). The appreciable bandwidth is achieved in such a small size antenna. The pass band frequency of MI waveguide is predicted by using the theoretical model of dispersion equation. The effective medium theory is used to verify the metamaterial characteristics of SSRR. The simulated results and theoretical calculations are also presented. The results show that the proposed method can be used to design compact and high bandwidth microstrip patch antennas.

Metamaterials design using gradient-free numerical optimization

We apply numerical optimization methods in combination with full-field electromagnetic simulations to tailor the broadband spectral response of gold and silver split-ring resonator metamaterials. A derivative-free, nonlinear mesh adaptive search technique was used to drive finite-difference time-domain simulations. This algorithm allows the designer to independently vary the spectral position of the two resonant peaks and their relative reflection amplitudes throughout a wide range of the near infrared. An application of this method is then shown to design split-ring resonator “notch filters,” with narrow pass bands at 1310, 1550, and 1800 nm which have an ∼45% change in reflectivity at the pass band and corresponding linewidths of ∼90 meV.

Experimental determination of the quadratic nonlinear magnetic susceptibility of a varactor-loaded split ring resonator metamaterial

This letter presents a quantitative measurement of the second harmonic generated by a slab of varactor loaded split ring resonator metamaterial and the retrieval of the effective quadratic nonlinear magnetic susceptibility χm(2) using an approach based on transfer matrices. The retrieved value of χm(2) is in excellent agreement with that predicted by an analytical effective medium theory model.