Double Split Ring Resonator Research Articles

A tunable double negative device consisting of a plasma array and a negative-permeability metamaterial

Extraordinary wave transmission is demonstrated through a double-negative composite comprised of a negative-permeability array of double split ring resonators and a negative-permittivity array of plasma discharge tubes at microwave frequencies. A transmission peak emerges in a double-negative band and controlling the electron density inside the plasma tubes dynamically regulates the transmission properties. By performing experiments and theoretical calculations, we verify that the composite permits wave propagation with negative permeability and controllable permittivity, which indicates that a tunable negative-refractive-index device is achieved.

Numerical and Theoretical Study of Tunable Plasmonically Induced Transparency Effect Based on Bright-Dark Mode Coupling in Graphene Metasurface.

In this paper, we numerically and theoretically study the tunable plasmonically induced transparency (PIT) effect based on the graphene metasurface structure consisting of a graphene cut wire (CW) resonator and double split-ring resonators (SRRs) in the middle infrared region (MIR). Both the theoretical calculations according to the coupled harmonic oscillator model and simulation results indicate that the realization of the PIT effect significantly depends on the coupling distance and the coupling strength between the CW resonator and SRRs. In addition, the geometrical parameters of the CW resonator and the number of the graphene layers can alter the optical response of the graphene structure. Particularly, compared with the metal-based metamaterial, the PIT effect realized in the proposed metasurface can be flexibly modulated without adding other actively controlled materials and reconstructing the structure by taking advantage of the tunable complex surface conductivity of the graphene. These results could find significant applications in ultrafast variable optical attenuators, sensors and slow light devices.

Ultra-Broadband Polarization Conversion Meta-Surface and its Application in Polarization Converter and RCS Reduction

In this paper, an ultra-broadband and high-efficiency polarization conversion metasurface is presented in the terahertz region. The metasureface is similar to a sandwiched structure, which is composed of the top Double Split Ring Resonator (DSRR), an intermediate dielectric layer and a bottom metal layer. Both numerical simulation and theoretical calculation results demonstrate that the proposed metasurface can convert linearly co-polarized waves into cross-polarized waves in the frequency from 2.04 THz to 5.33 THz with a relative bandwidth of 89% and the polarization conversion ratio (PCR) is over 90%. Further simulation results show that the proposed metasurface is insensitive to the polarization angle, and the physical mechanism is revealed in detail by the surface current distribution. In addition, two different kinds of 2-bit coding metasurfaces are designed based on the Pancharatnam-Berry (PB) Phase. The simulated and calculated results show that the proposed PB-coding metasurface has excellent performance in flexibly controlling terahertz wave reflection and low Radar Cross Section (RCS). A 10dB RCS reduction can be achieved from 1.9 THz to 5.5 THz under normal incidence. It provides new degrees of freedom for studying terahertz wave manipulation and reducing RCS.

Ultrasensitive THz biosensor for PCR-free cDNA detection based on frequency selective surfaces.

THz technologies are a powerful tool for label-free detection of biomolecules. However, significant reduction of the lower detection limit is required to apply THz-sensors in biomedical diagnosis. This paper reports an ultrasensitive THz-biosensor based on asymmetric double split ring resonators (aDSRR) for the direct label- and PCR-free detection of DNA at physiologically relevant concentrations. We introduce selective functionalization and localized electric field concentration to enhance aDSRR sensitivity and specificity. The sensor characteristics are demonstrated using the human tumor marker MIA in cDNA samples produced from total RNA without PCR-amplification. Measurements of DNA samples with concentrations as low as 1.55 × 10-12 mol/l are presented.

Detection of Water Quality using Defected Ground Double Split Ring Resonator

Water is an essential thing for life. Now days due to population growth and pollution, the quality of water is degraded. In this paper, a single element double split ring resonator (DSRR) has been presented as a sensor to detect the quality of water. Here, two square shape metallic split rings are designed along with the microstrip line. On the back side of the substrate, defected ground structure (DGS) is introduced. The resonant frequency of the resonator is 11.12 GHz. Quality of water is detected by the shift in S21 resonant frequency with the variation in transmission coefficient. This sensor can be used in our daily life to detect the quality of water and it may be useful in medical field also.

Bandwidth enhancement of five-port reflectometer-based ENG DSRR metamaterial for microwave imaging application

A five-Port Reflectometer (FPR) with the integration of ultra-wideband (UWB) Epsilon Negative (ENG) Double Split Ring Resonator (DSRR) metamaterial array is introduced in this paper for microwave imaging (MWI) application. The designed DSRR consists of two concentric rings with a split in each which are spatially rotated by 180°, formed an inverted structure to exhibit a wide negative epsilon bandwidth of 187 % (from 0.5 GHz to 15 GHz). The FPR is designed using a ring junction topology and semi-circularly curved inter-port transmission lines (TLs) which are placed between five equally spaced ports. Localizing the DSRR metamaterial in a periodic array of 5 × 4 at the ground plane of FPR lead to 79.79 % fractional bandwidth and reflection coefficient within the operating frequencies of 0.991 GHz–2.2576 GHz. Equivalent circuit model has been alluded with an intricate description of different array configurations of the metamaterial unit cell. Comparison of EM simulation and circuit simulation has been performed to validate the equivalent circuit model. It is found that the existence of stray capacitance, Cstray which is represented by the DSRR configurations, significantly influenced the resonant frequency and bandwidth of FPR. Measured results of the proposed design suits well with the simulations and prove higher efficacious applicability of the proposed design for microwave imaging application. A comparison of the reconstructed image also proves its suitability for the microwave imaging application.

Transmission control by asymmetric electromagnetically induced transparency-like metamaterials in transverse electromagnetic waveguide

Abstract We numerically and experimentally present passive and active electromagnetically induced transparency-like metamaterials in a TEM waveguide under normal excitation. Asymmetry of the metamaterial unit cell leads to the splitting of the radiative resonance. Surface current distributions are analyzed to account for each resonance. Moreover, by implementing a varactor diode to one of the gaps of the double-split ring resonator, electromagnetically induced transmission-like band is shifted in frequency and the corresponding bandwidth is modulated. A modulation ratio of 29.5 dB in transmission is experimentally demonstrated by only increasing the bias voltage 4 volts.

Terahertz radiation field distribution manipulation by metasurface with graphene substrate

Abstract Terahertz radiation field distribution manipulation gains increasing attention from both science and technology, but available mechanisms are hard to implement it. We design two asymmetric double-split ring resonators (DSRRs) based on theoretical analysis to realize terahertz radiation field distribution manipulation by metasurface with graphene substrate. Here we show that in principle the dynamic intensity regulation of left-handed circularly polarization (LHCP) and right-handed circularly polarization (RHCP) components can be realized by satisfying certain condition, which is derived from electro-optical effect of graphene in terahertz region. Furthermore, we show that the spatial angle control of LHCP and RHCP components can be realized by designing the arrangement and combination of meta-atoms based on Pancharatnam-Berry (PB) phase. Terahertz radiation field distribution manipulation not only promotes the sensing of terahertz micro-devices, but also facilitates the multifunctional control of holographic projection.

Experimental realization of electromagnetic toroidal excitation for microwave applications

An experimental realization of resonant toroidal dipole excitation in the microwave regime is presented in this paper. The metasurface proposed herewith is an asymmetric double split-ring resonator exhibiting Fano-like resonance profile. One could observe that cascading the metasurface results in near-field transverse and longitudinal coupling creating dual-band toroidal moments on the structure. This planar scheme will simulate the development of enhanced light–matter interaction, electromagnetic wave slowdown and sensor design. Here we report the experimental realization of the phenomenon in the S-band frequencies, and the results are verified using multipole scattering analysis.

A finite element method towards acoustic phononic crystals by weak formulation

A weak formulation method is presented to analyze the propagation of acoustic waves in periodic crystal-like systems called phononic crystals. First, a compact circle and double split ring resonators with high impedance contrast to air background are employed to compute band structures with not only real parts of wavevectors but also imaginary parts of them. Calculating the imaginary part, which directly predicts a propagation length in band gaps, is not readily available in previous studies. It analytically enables us to more understand the behavior of evanescent mode in band gaps. Moreover, we present that the weak formulation method is advantageous in calculating equi-frequency contour.

Terahertz optical characteristics of two types of metamaterials for molecule sensing.

We investigate spectral responses of two different terahertz (THz) metamaterials of double split ring resonator (DSRR) and the nano slot resonator (NSR) for molecule sensing in low concentration. Two different resonant frequencies of DSRR can be controlled by polarization angle of incident THz beam. For comparison of THz optical characteristics, two NSRs were made as showing the same resonant frequencies as DSRR's multimode. The monosaccharide molecules of glucose and galactose were detected by these two types of metamaterials matching the resonant frequencies in various concentration. NSR shows higher sensitivity in very low concentration range rather than DSRR, although the behavior was easily saturated in terms of concentration. In contrast, DSRR can cover more broad concentration range with clear linearity especially under high quality factor mode in polarization of 67.5 degree due to the Fano resonance. THz field enhancement distributions were calculated to investigate sensing performance of both sensing chips in qualitative and quantitative manner.

Gain and Bandwidth Enhancement of Microstrip Antenna Array using Double Square Split Ring Resonator FSS as a Superstrate for WiMax/WiFi/WLAN Applications

Gain and Bandwidth Enhancement of Microstrip Antenna Array using Double Square Split Ring Resonator FSS as a Superstrate for WiMax/WiFi/WLAN Applications

Pneumatically tunable microwave split ring resonators

We have investigated the operation of a coupled system of double split ring resonators (SRRs) to demonstrate the tunability by changing its physical layout. A pneumatic system is proposed to dynamically shift the structural arrangement of the coupled SRRs in response to the incident electromagnetic wave. It is executed by manipulating the lateral placement of the levitated bottom ring relative to the static ring in the top layer using various levels of pneumatic force. We reduced the electromagnetic interference by avoiding metallic components and improved the stability through the contactless operation. The proposed pneumatic system uses only the air to modulate the operational frequency of the coupled SRRs. Both the simulation and the experiment have shown the transition between the quasi-edge coupled and the broad-side coupled modes of the double SRRs shift the resonance frequency over 28% around 3.0 GHz. This pneumatic implementation brings a new method of reconfigurable SRRs.

Suppression of mutual coupling in rectangular dielectric resonator antenna arrays using Epsilon-Negative metamaterials (ENG)

ABSTRACTA double slotted symmetrical split ring resonator with an inductive stub in its inner ring is presented as a Single Negative Electric (SNG) metamaterial to suppress mutual coupling between two E-plane coupled microstrip line fed rectangular dielectric resonator antenna (RDRA) array. The proposed SRR exhibits two resonant frequencies and wide stop-bands. The -10 dB bandwidth of S21 from 2022MHz to 2720 MHz and from 2187 MHz to 3839 MHz are obtained for the first structure, #1, and the second structure, #2, respectively. By introducing an ENG layer between the two RDRAs, the experimental reduction in mutual coupling is more than 23 dB with a small frequency shift (∼ 20 MHz), while the impedance matching is improved. The radiation efficiency and total efficiency are increased while the far-field pattern in the E-plane is not disturbed.

Experimental investigations of wave-DSRR interactions in liquid-phase media

In this paper, the mechanical displacement and the resulting resonance shift of a basic double split ring resonator (DSRR) which is placed in different low-loss liquid-phase environments are experimentally demonstrated. Such resulting dynamic process is due to the wave-DSRR interactions and the induced electromagnetic attraction force when an incident electromagnetic wave with enhanced intensity acts on the DSRR. Low-loss liquids including polyalphaolefin and polydimethylsiloxane are used in this paper as the host media to clearly show the electromagnetic resonance and its resonance shift performances. These experimental investigations and the obtained results can create a completely different research direction for the application of metamaterials in liquid-phase environments.

Fano-resonance collapse induced terahertz magnetic dipole oscillation in complementary meta-atoms via local symmetry breaking

A novel phenomenon is observed in the meta-atoms composed of a complementary rectangular double split-ring resonator (SRR). An intrinsic Fano-resonance collapses with the outer SRR deformed asymmetrically. Alternatively, a trapped mode emerges at an adjacent frequency region, of which its strength grows up with increasing the asymmetric deviation. However, the asymmetric deformation in the inner SRR has influence neither on the evolution of this intrinsic Fano-resonance nor on the excitation of the aforementioned trapped mode. The results of electromagnetic field simulation indicate that an interference of two magnetic dipoles leads to the intrinsic Fano-resonance on the outer SRR. The asymmetric deviation destructs coherent interference so that the Fano-resonance collapses. To the trapped mode, the surface current passes through the metal gap of the outer SRR, leading to a couple of antiparallel currents, which results in a couple of magnetic dipole oscillations. The intrinsic modes are kept constant, even though the inner SRR is asymmetrically deformed. The outer SRR plays the role of a Faraday cage, which electromagnetically shields the trapped mode on the inner SRR.

Tunable graphene-silica hybrid metasurface for far-infrared frequency

We present graphene-based metasurface structure that is actively tuned over far infrared frequency range. Tunable metasurface is created by using single ring and double ring split ring resonator (SRR) and complementary split ring resonator (CSRR). Proposed metasurface structures are analysed over different graphene chemical potential. Results of different metasurface are compared in terms of their transmittance, reflectance, phase variation and phase difference. The modulation depth of the transmittance is achieved more than 90%. It is also observed that resonance response becomes stronger when higher chemical potential is applied to graphene metasurface. The designed graphene metasurface can be used as sensor, polarizer and modulator in modern photonics devices.

Actively tunable slow light in a terahertz hybrid metal-graphene metamaterial

We theoretically and numerically demonstrate an actively tunable slow light in a hybrid metal-graphene metamaterial in the terahertz (THz) regime. In the unit cell, the near field coupling between the metallic elements including the bright cut wire resonator and the dark double split-ring resonator gives rises to a pronounced transmission peak. By positioning a monolayer graphene under the dark mode resonator, an active modulation of the near field coupling is achieved via shifting the Fermi level of graphene. The physical origin can be attributed to the variation in the damping rate of the dark mode resonator arising from the conductive effect of graphene. Accompanied with the actively tunable near filed coupling effect is the dynamically controllable phase dispersion, allowing for the highly tunable slow light effect. This work offers an alternative way to design compact slow light devices in the THz regime for future optical signal processing applications.

Amplitude modulation of anomalously reflected terahertz beams using all-optical active Pancharatnam-Berry coding metasurfaces.

Pancharatnam-Berry (P-B) metasurfaces introduce geometric phases to circularly polarized electromagnetic waves through geometric rotation of the unit cells, thereby converting spin angular momentum (SAM) to orbital angular momentum (OAM) of photons and achieving flexible modulation of spin-polarized waves. It is highly desirable for dynamically tunable P-B metasurfaces to be actively applied. Here, combining double split-ring resonators (DSRRs) with photosensitive semiconductor germanium (Ge), we propose three types of all-optical active Pancharatnam-Berry coding metasurface for dynamic amplitude modulation of spin waves and vortex beams in the terahertz band. Coupled with signal processing methods such as the convolution operation, optical active P-B coding metasurfaces show a strong regulation effect on terahertz beams. This opens up a broad path for coding metasurface applications such as high-speed wireless terahertz communications.

High throughput and label-free particle sensor based on microwave resonators

We developed a novel particle sensor based on micro channels embedded in microwave resonators, which are fabricated by standard print circuit board manufacturing technology. The sensing frequency falls in the range 2–4 GHz, the widely used microwave S band. A 70 μm-particle can produce a frequency shift of 0.5 MHz in a sensor with 150 μm channel size, with a dwell time of 0.5 ms by using double split ring resonators. These resonator sensors may employ phase-locked loop in achieving a higher detection resolution.