Array Of Split-ring Resonators Research Articles

Ultraviolet Sharp High-Order Magnetic Plasmon Based Fano Resonance of 3D Metamaterials

We theoretically study the ultraviolet sharp Fano resonances (FRs) produced through the optical diffraction coupling between the narrow collective surface mode supported by the array periodicity and the broad high-order magnetic plasmon (MP) mode in the three-dimensional (3D) metamaterials consist of aluminum vertical split-ring resonator (Al 3D-SRR) array. The linewidth of the second-order MP induced ultraviolet FR is as narrow as 7.3 nm due to the diffraction coupling feature of the magnetic fields. The intensity and position of the ultraviolet sharp FR are easily tuned by varying the array period as well as the base and arm length of the Al 3D-SRR structure. The conventionally defined performance index of optical sensors, sensitivity ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$S$ </tex-math></inline-formula> ) and figure of merit ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">FoM</i> ) of our designed 3D metamaterial in the ultraviolet range, possess quite large values of 88 nm/RIU and 12, respectively.

Terahertz Resonators Based on YBa2Cu3O7 High-Tc Superconductor

Superconducting split-ring resonator arrays allow to overcome two main limitations affecting metallic metamaterial resonating in the terahertz (THz) range: ohmic losses and tunability of their optical response. In this work, we design and experimentally realize direct and complementary square arrays of superconducting YBa2Cu3O7 (YBCO) split-ring resonators working in the THz spectral range. The main purpose of this paper is to show how the metamaterial resonances can be tuned by temperature (T) when crossing the superconducting transition temperature Tc of YBCO. The tuning property can be quantified by describing the THz transmittance of the patterned YBCO films vs. T through a model of coupled resonators. This model allows us to estimate the THz resonances of split-ring arrays and their interaction, showing how the kinetic inductance Lk in the superconducting state is the main parameter affecting the metamaterial properties.

Far-Field Decoupling of Two-Element Antenna Transceiving System by the Periodic Near-Field Resonators

In this letter, a hybrid wideband decoupling method based on far-field radiation regulation by employing the specially engineered periodic near-field resonators, which consist of split-ring resonator (SRR) arrays, is presented for the two collinear transceiving horn antennas with extremely large element spacing. Two E-plane-coupled antennas operating at X-band are arranged with center-to-center distance of 8 m (over 200λ). By allocating the SRR arrays in close proximity to each horn antenna, the radiation power in the specified horizontal directions pointing to each other could be significantly reduced without disturbing their radiation characteristics in the broadside thus leading to the conspicuous port isolation enhancement. It is validated that more than 25 dB mutual coupling level reduction is achieved over the frequency range of 8–11.5 GHz (∼35.9% fractional bandwidth) when the SRR arrays are integrated. Finally, a prototype was fabricated and measured. Corresponding measurement results are in good agreement with the simulated ones.

Investigations on Complementary Split Ring Resonator (CSRR) array integrated printed conformal band pass filters for modern wireless communication applications

This paper presents the performance analysis of two different conformal band pass filters (BPFs) loaded with an array of circular complementary split ring resonators (CSRRs). Type-1 bandpass filter has been designed by integrating a 9 × 9 array of circular complementary split ring resonator on the bottom layer of the filter. Similarly, Type-2 bandpass filter has been constructed by loading an array of 5 × 5 split ring resonator on the patch layer of the filter. A comparative study between Type-1 and Type-2 bandpass filters are also evaluated that shows dual pass bands for Type-1 filter and triple pass bands for the Type-2 bandpass filter. Furthermore, the conformality of both bandpass filters are judged through bending deformation analysis with various bending positions at 15°, 30°, 45°, 60° and 90°. During the bending performance analysis, the suggested BPFs retains the dual and triple pass band characteristics without any major deviations in its characteristic's parameters. Various performance parameters like return loss, insertion loss, group delay, bandwidth, and quality factor are measured. Detailed analysis of E and H field distributions and surface current distributions are also presented. The Type-2 bandpass filter shows better performance in terms of filter properties compared to Type-1 band pass filter. Hence, the prototype of Type-2 filter with an area of 30 × 30 mm2 is fabricated and measured. The validated results are agreed with the simulated results which confirms the applicability of the proposed filter for several modern wireless communication applications such as Wi-Max and personal communication systems (PCS) applications.

Experimental demonstration of multiple Fano resonances in a mirrored array of split-ring resonators on a thick substrate

This work demonstrates the first experimental observation of multiple Fano resonances in the terahertz range in a system based on an array of mirror-symmetric split-ring resonators deposited on low-loss and low-refractive index polytetrafluoroethylene (PTFE) substrate. For the first time, selective surface activation induced by laser technology has been used to deposit a copper layer on a PTFE substrate with the further application of standard mask lithography for metasurface manufacturing.

Self-assembled pagoda-like nanostructure-induced vertically stacked split-ring resonators for polarization-sensitive dichroic responses

Stacked split-ring resonators (SSRR) arrays exhibiting polarization-sensitive dichroic responses in both visible and near-infrared wavelengths are realized over a centimeter-scale large area. The SSRR arrays are derived from pagoda-like nanorods fabricated from the self-assembly of a lamellae-forming polystyrene-b-poly (methyl methacrylate) copolymer (PS-b-PMMA) confined in cylindrical pores of anodized aluminum oxide (AAO) template. Along the nanorod direction, PS and PMMA nanodomains were alternately stacked with the same distance. Silver crescents and semi-hemispherical covers, which are essential for SSRR with the polarization sensitivity, were obliquely deposited on the single side of the nanorod after removing the AAO template and reactive-ion etching treatment. These sophisticated nanoscale architectures made by bottom-up fabrication can be applied to structural color, optical anti-counterfeiting, and commercial optical components in a large area.

Design and analysis of a dual-band THz metamaterial sensor with high refractive index sensitivity

A terahertz metamaterial comprised of an array of cross rectangular split-ring resonators (CRSRR) was proposed and analyzed for sensing applications, and it exhibited two resonances in the frequency range of 0.2–3 THz. The resonant frequencies of different resonant modes were explained using equivalent circuit models. Furthermore, the influence on equivalent capacitance and inductance of the circuit with respect to different geometrical dimensions of the CRSRR structure were analyzed, and the results indicated that the resonant frequencies of the proposed metamaterial can be designed as the desired value by adjusting the CRSRR unit geometry. In addition, the sensing performances of the metamaterial were calculated based on the optimized structure, showing that it had high refractive index sensitivity of 309 and 730 GHz/RIU at two resonant frequencies, respectively. Meanwhile, such ability to operate at two frequency bands enabled the designed sensor could characterize the identical samples at different frequencies, thereby increasing the sensing sensitivity and decreasing the impact of environmental disturbance. Our study opens up new prospects in the design of terahertz metamaterial sensors with high sensitivity in a multi-band range, which is essential to meet increasing needs in terahertz sensing.

Guided Lattice Modes in Terahertz Metasurface Deposited on Ultrathin Dielectric Substrate

Propagation of tangential electromagnetic modes in array of split-ring resonators deposited on a thin dielectric plate is analyzed by studying the Fano resonance and electromagnetically induced transparency, which appear in the transmission spectra due to the coupling of these modes with the third plasmonic mode of the split-ring resonators. We determine the spatial dependence of the electric and magnetic field enhancement in these systems, showing a noticeable difference between diffracted modes in free-standing resonators and guided modes in the presence of a dielectric plate. We find that in the case of a subwavelength dielectric thickness, the in-plane modes are guided by both interference and internal reflections of diffracted waves. Numerical simulation is confirmed by analytical modeling and experimental data.

Demonstration of dipole-induced transparency using mirrored split-ring resonator metasurface for microwave applications

In this paper, the Dipole-Induced Transparency (DIT) in the microwave frequency regime is proposed and verified using experimental and simulation studies. A single-layer mirrored Split-Ring Resonator (SRR) array configured in the H⊥ excitation scenario is used to create an out-of-phase oscillating electric dipole moment for a normal incident plane wave. The destructive interference between these out-of-phase oscillating electric dipole moments nullifies far-field scattering resulting in the emergence of the transparency window. We used the multipole scattering theory to validate the results computationally. The coupling effects are studied numerically, and the emergence of the transparency window is studied experimentally using transmission measurements inside an anechoic chamber using a vector network analyzer.

Development of a Flexible Metamaterial Film with High EM Wave Absorptivity by Numerical and Experimental Methods.

The present study is intended to develop and test a cost-effective and efficient printing method for fabricating flexible metamaterial film with high electromagnetic wave absorptivity. The film can be easily applied to the surfaces with curved aspects. Firstly, numerical parametric study of the absorption characteristics of the film is performed for the range of frequency varying from 2.0 to 9.0 GHz based on commercial software package. Secondly, the flexible metamaterial films are fabricated, and experiments are conducted. The flexible metamaterial film consists of a flexible dielectric film made of polyimide (PI) and an array of split-ring resonators. The split-ring resonators of different geometric dimensions are fabricated on the PI film surface by using a silver nanoparticles ink jet printer. The performance of the flexible structure is then measured and dependence of operation frequency with higher absorptivity on the dimensions of the split-ring resonators is investigated. A comparison between the numerical and experimental data shows that the numerical predictions of the operation frequency with higher absorptivity closely agree with the experimental data.

Making a meta-surface soliton-ready

Abstract Metamaterials attracted significant attention due to their unprecedented properties in the electromagnetic domain. However, they are facing challenges while putting for applications due to the strong dispersion associated with the resonant responses and high losses. In this communication, we present a path to overcome these problems by turning the propagating electromagnetic wave into a soliton wave that can sustain dispersion and loss. For theoretical demonstration, we considered a hybrid 2D metamaterial that consists of arrays of split-ring resonators on a graphene layer. We identified the parametric region that ensures dispersion and loss less propagation of electromagnetic wave in form of a dissipative soliton. This approach can be applied to a large variety of metamaterials and metasurfaces for which a set of coupled rate equation is available.

Chest-Worn Heart Rate Variability Monitor With a Self-Injection-Locked Oscillator Tag

This article presents a chest-worn device for monitoring the heart rate variability (HRV) of a person in motion without direct contact with the skin. The device operates at 5.8 GHz and mainly consists of a self-injection-locked oscillator (SILO) and a tag antenna. The device transmits the output signal of an SILO that is frequency-modulated (FM) by the Doppler effect of the physiological movement of the chest via the tag antenna to a remote FM receiver. Accordingly, the heartbeat is detected and the HRV can be estimated. The tag antenna comprises a circularly polarized ring slot antenna and a split-ring resonator (SRR) array in stack to enhance sensing directivity while reducing the moving clutter in the joint sensing and transmission process. For validation, an HRV monitoring system was developed, based on the proposed device, to detect the cardiac intervals of a wearer who performs various activities, including walking and running. The results thus obtained agree closely with electrocardiogram (ECG) measurements.

Optimization of plotter printing for sub-terahertz metallic metasurfaces fabrication on ultra-thin substrate

Additive manufacturing processes have emerged as a promising way to conceive terahertz and millimetric components. In this work, we discuss a printing process for sub-terahertz metallic metasurfaces fabrication on ultra-thin substrates. We demonstrate the use of a plastic substrate with a micrometric thickness which makes this printing method a promising and low cost alternative to conventional optical lithography for the fabrication of flexible terahertz 2D metasurfaces. After detailing the key parameters and limitations, we applied the optimized process to fabricate samples composed of periodic arrays of split ring resonators on 50 µm thick fused silica and 3 µm thick PET substrates. The optical response in transmission of the metasurfaces shows expected resonances in the 100 GHz range and demonstrates the use of microplotter system for rapid prototyping of low-loss terahertz passive components on ultra-thin substrate.

Transflective spatial terahertz wave modulator

Spatial light modulators can digitally manipulate the amplitude, phase, and polarization of light. Their counterparts in the terahertz band are highly pursued to meet the requirements of numerous applications such as wireless communications and biomedical detection. Here, we propose a spatial terahertz wave modulator based on a liquid-crystal-integrated metadevice. The modulator consists of 8 × 8 pixels. The liquid crystal layer is sandwiched between an asymmetric split ring resonator array and pixelated interdigital electrodes. Fano resonance occurs for the transmitted wave, while the reflected wave is perfectly absorbed. By separately driving the liquid crystal with pixelated interdigital electrodes, both the Fano resonance and absorption peak can be continuously tuned due to the variation in the environmental refractive index. This work provides a transflective spatial terahertz wave modulator that can dynamically reconfigure a terahertz wavefront.

Mode coupling based on split-ring resonators and waveguide and second harmonic enhancement

Nonlinear optical processes are promising for many applications, and recently great attention has been paid to improve the nonlinear efficiency of plasmonic metasurfaces. Here, we propose a hybrid structure consisting of a gold split-ring resonator (SRR) based nonlinear metasurface on top of a dielectric waveguide layer. By adjusting the periodicity of the SRR array, we demonstrate that the coupling between the magnetic surface plasmons (MSPs) of the SRRs and the waveguide modes could greatly enhance the second harmonic generation (SHG) intensity. Compared with the conventional SRR arrays, the hybrid structures could provide an extra enhancement in the SHG intensity of more than one order of magnitude.

Comparison of second harmonic generation from cross-polarized double-resonant metasurfaces on single crystals of Au

Abstract Second harmonic generation (SHG) from metasurfaces consisting of square array of split ring, heptagon and triangle cross-polarized double resonant resonators, is investigated both experimentally and numerically. The structures are fabricated on single crystalline Au plates using Focused Ion Beam technique. Array of the triangular structure exhibits most efficient SHG. Experimental observation is explained reasonably well by theoretical evaluation of SHG using the overlapping integral of nonlinear polarization and the microscopic field distribution on the metal surface at the SHG frequency taking phase relation between the two fields into account.

Tunable graphene quadrupole dark mode based ultranarrow Fano resonance in asymmetric hybrid metamaterial

We numerically demonstrate the ultranarrow high-order Fano resonance generated by the plasmonic coupling between graphene quadrupole dark mode and metallic bright magnetic dipole mode due to structural symmetry breaking effect in asymmetric hybrid metamaterials, consisting of periodic arrays of graphene nanoribbon and gold split-ring resonators. The graphene quadrupole Fano curve presents an ultranarrow lineshape with quality (Q) factor of 40. The proposed metamaterial shows the obvious dependence of the structural parameters and Fermi energy. Our designed asymmetric hybrid metamaterials shows a high sensitivity of 4.2μm/RIU and figure of merit (FOM) of 30, which could pave way for in label-free biomedical sensing.

Graphene-Based Multiband Chiral Metamaterial Absorbers Comprised of Square Split-Ring Resonator Arrays With Different Numbers of Gaps, and Their Equivalent Circuit Model

The equivalent circuit model (ECM) is developed by using a MATLAB code to analyze graphene-based multi-band chiral metamaterial absorbers composing graphene-based square split-ring resonator arrays in the terahertz (THz) range. The absorbers are simulated numerically by the finite element method (FEM) in CST Software to verify the ECM results. Our introduced multi-band absorbers can be used as suitable platforms in polarization-sensitive devices and systems in the THz range. We have designed four tunable graphene-based chiral metamaterial absorbers containing one, two, three, and four gaps in their arms, respectively. The absorber with one gap has four absorption bands (two for TE and three for TM, one band of both modes approximately overlaps) with absorption &#x003E; 50%. The absorber with two gaps has three absorption bands (two for TE and two for TM, one band of both modes approximately overlaps). The absorber with three gaps has four absorption bands (three for TE and two for TM, one band of both modes approximately overlaps). The absorber with four gaps has three absorption bands (three for TE and two for TM, two bands of both modes approximately overlap). They work in the 1-5.5 THz with maximum linear dichroism (LD) responses of 98, 99, 89, and 77%, respectively. The designed absorbers are dynamically tunable. Additionally, by a 90&#x00B0; rotation of the incident electromagnetic fields, it is possible to switch between the number and/or location of absorption bands making these absorbers a promising candidate for future THz systems. ECM results are following the FEM ones. The proposed ECM procedure is a simple and fast way to recognize the characteristics of the designed absorbers. Our proposed absorbers could be promising enablers in future THz systems.

Liquid Metal-Based Microfluidic Metasurface for Controllable Electromagnetic Wave Reflection Attenuation

We demonstrated a liquid metal based microfluidic chip that enabled consistent, continuous and large liquid metal unit structure array reconfiguration. The chips were assembled into a metasurface, which preliminary achieved controllable electromagnetic wave reflection attenuation. The chip contained a 5 &#x00D7; 6 Galinstan split-ring resonator (SRR) array, and the SRRs could be reconfigured continuously by NaOH solution pressure driven. A fin shaped microvalve was designed and integrated onto the chip, which could withstand a high fluid driving pressure (over 210 kPa), so the SRRs could be reconfigured with a large split angle. The flow resistance of each SRR chamber was analyzed for consistent and robust SRRs deformation. The SRRs enabled more than 250&#x2218; reconfiguration and showed consistent deformation with a standard derivation less than 8.5&#x2218;. The metasurface showed 7.5 dB and 13.5 dB attenuation at 3 GHz and 4 GHz respectively. Also, with the different split angles, there could be three attenuation peaks that reach -10 dB when the frequency ranged from 2.9-3.1 GHz, 3.7-4.2 GHz and 4.8-5.0 GHz, respectively. The metasurface we proposed can be potentially used in multiband controllable electromagnetic wave absorption.

High-efficiency modulation of broadband polarization conversion with a reconfigurable chiral metasurface

We demonstrate an electrically biased reconfigurable chiral metasurface for controlling the polarization conversion and asymmetric transmission in a broadband manner. The reconfigurable metasurface is constructed with coupled three-layer complementary split-ring resonator (CSRR) arrays and is loaded with tunable electronic components to achieve dynamic control of reconfigurable chiral coupling in the CSRRs by simply tuning the external voltage on the structure. It is found that the polarization conversion in the metasurface can be effectively and continuously tuned in both experiments and simulations in a broadband frequency range. Meanwhile, the reconfigurable metasurface shows an asymmetric transmission (AT) effect in a broadband range for a polarized wave. The proposed reconfigurable chiral metasurface based on the active tuning of connection in the meta-structure with few functional layers is confirmed as an effective strategy for multi-functional polarization manipulation. The reported broadband properties of the chiral metasurface are promising for polarization manipulation in optical bands and applications in wireless communication.