Double Split Ring Resonator Research Articles

High efficient bi-functional metasurface with linear polarization conversion and asymmetric transmission for terahertz region

Abstract Polarization control is crucial in contemporary photonics, but achieving broad bandwidths and high efficiencies remains a significant challenge. Here, we propose a wideband and high-efficiency metasurface designed for linear polarization conversion and asymmetric transmission (AT) in the terahertz region based on a three-layer chiral structure. By integrating a double-split ring and strip resonator, the design can improve both wide bandwidth and high-efficiency cross-polarization conversion and AT capabilities for a linearly polarized wave. The operating band for AT is 0.73-3.01 THz with an efficiency above 0.8, while the polarization conversion ratio exceeds 0.99 across the 0.56-3.94 THz range. The underlying physical mechanism behind wideband transmission polarization conversion was fully elucidated through theoretical analysis and the characterization of surface current distribution. This designed structure can be used in terahertz imaging, sensing, and communication.

Design and development of graphene-based double split ring resonator metasurface biosensor using MgF2-gold materials for blood cancer detection

Design and development of graphene-based double split ring resonator metasurface biosensor using MgF2-gold materials for blood cancer detection

High-Q factor terahertz metamaterial sensor based on quasi-BIC

In this paper, we proposed a terahertz (THz) metamaterial sensor, which consists of an array with two mirrored double split ring resonators (DSRRs) in one unit cell deposited on a lossless polyimide substrate. The THz spectral response show that when the two DSRRs in one unit cell are mirror symmetric and center symmetric simultaneously, two types of symmetry-protected bound states in the continuum (BICs) can be generated with the incident polarization unchanged. When the gaps are on the short or long arms of DSRRs, different modes of BIC can be observed. By breaking the symmetry of the structure with the gaps deviating from the center line of the DSRRs, quasi-BICs can be achieved, which can provide high Q-factors for our designed THz metamaterial sensor. The performance of the sensor is also evaluated, which has the characteristics of high Q-factor, high sensitivity, and high linearity. The integration of quasi-BIC and THz sensing technology will help solve the problems faced in the design of ultra-high Q-factor THz sensors and further expand the applications of terahertz technology.

De-embedding method for a sensing area characterization of planar microstrip sensors without evaluating error networks

A de-embedding method for determining all scattering (S-) parameters (e.g., characterization) of a sensing area of planar microstrip sensors (two-port network or line) is proposed using measurements of S-parameters with no calibration. The method requires only (partially known) non-reflecting line and reflecting line standards to accomplish such a characterization. It utilizes uncalibrated S-parameter measurements of a reflecting line, direct and reversed configurations of a non-reflecting line, and direct and reversed configurations of the sensing area. As different from previous similar studies, it performs such a characterization without any sign ambiguity. The method is first validated by extracting the S-parameters of a bianisotropic metamaterial slab, as for a two-port network (line), constructed by split-ring-resonators (SRRs) from waveguide measurements. Then, it is applied for determining the S-parameters of a sensing area of a microstrip sensor involving double SRRs next to a microstrip line. The root-mean-square-error (RMSE) analysis was utilized to analyze the accuracy of our method in comparison with other techniques in the literature. It has been observed from such an analysis that our proposed de-embedding technique has the lowest RMSE values for the extracted S-parameters of the sensing area of the designed sensor in comparison with those of the compared other de-embedding techniques in the literature, and have similar RMSE values in reference to those of the thru-reflect-line calibration technique. For example, while RMSE values of real and imaginary parts of the forward reflection S-parameter of this sensing area are, respectively, around 0.0271 and 0.0279 for our de-embedding method, those of one of the compared de-embedding techniques approach as high as 0.0318 and 0.0324.

Dual-band terahertz metamaterials with electromagnetically induced transparency-like enabling high-performance sensing

In this paper, a high-performance metamaterial sensor with a square split-ring resonator and a double circular split-ring resonator is proposed, which can simultaneously excite broad-band and narrow-band electromagnetically induced transparency-like (EIT-like) effects in the terahertz band. First, the mechanisms of the dual-band EIT-like effects have been revealed by the analyses of the transmission spectra and surface current distributions in the metamaterial. Then, the influences of structural parameters on the dual-band EIT-like are discussed further. Finally, the metamaterial is very sensitive to the change of the refractive index of the surrounding media, and the sensitivity of the dual-band EIT-like resonances can reach 150 GHz/RIU and 237.5 GHz/RIU and the quality factor values are 1.67 and 7.92, respectively. The proposed metamaterial broadens the pathway for the excitation of multi-band EIT-like effects and offers promising applications in multi-frequency sensors, filters and many other aspects.

Tunable asymmetric square split ring resonator based triple band metamaterial absorber for wireless communication system

This article presents a triple band square split ring with double circular split ring resonator incident angle-insensitive perfect metamaterial absorber. The MMA unit cell was manufactured using a FR4 substrate that had dimensions of 8 mm by 8 mm. With the flexibility of on-design adjusting of the highest absorption frequencies, the suggested MA displays peak absorption of 99.67 %, 99.85 %, and 99.97 % at 2.52 GHz, 6.99 GHz, and 9.28 GHz, correspondingly. The tuning metallic two circular split rings and square split ring resonator provide the possibility of frequency modification throughout three distinct frequency ranges: the first frequency range extends from 2.45 GHz to 2.53 GHz, the second frequency range extends from 6.91 GHz to 7 GHz, and the third frequency range extends from 8.85 GHz to 10.32 GHz. Furthermore, the suggested MA displays near-zero absorption at an oblique incidence angle of up to 45° for both the TE as well as TM modes. The unit cell demonstrates single negative properties, such as an effective medium ratio (EMR) of 14.88 and a quality factor (Q factor) that is more than 30 for both the TM mode as well as the TE mode. An equivalent circuit successfully demonstrated its performance capability, which indicated that it would create an MMA of good quality when using ADS software. A comparison between the measured results of the suggested MMA and the simulated one reveals that there is a significant amount of a similarity between both of them. Because of its easy design within small dimension, wide angular stability, strong absorption, good EMR, and flexibility to frequency tuning is suitable for a wide range of wireless communication system, especially satellite applications like electromagnetic interference reduction, radar systems, imaging, and stealth technology.

Tunable dual-functional metasurface for wideband cross-polarization conversion and wideband absorption

This work presents a tunable and wideband dual-functional metasurface (DFM) operating in the terahertz regime with highest overlap bandwidth (OBW). The structure consists of a double-split ring resonator and a meandered square ring resonator based on VO2 to achieve reflective cross-polarization conversion and absorption functionalities, respectively. When the phase changing material VO2 is in its metallic state, the metasurface acts as a perfect absorber with a peak absorption of ≥ 90% over the operating band of 2.3–4.01 THz. When VO2 is in its insulating state, the metasurface acts as a reflective cross-polarization converter over a wideband from 1–4.1 THz with high polarization conversion ratio of ≥ 90%. The proposed DFM has a stable response up to 45∘ of incidence in the polarization converter state and 60∘ of angular stability under the absorber state. Further, tunability is achieved by integrating photoconductive silicon and controlling the optical pump intensity in the double-split ring and meandered . square ring resonators. The proposed metasurface finds its applications in security, detection and THz communication systems.

Manipulation on radiation angles via spatially organized multipoles with vertical split-ring resonators

Abstract Herein, the radiation patterns of single-split ring resonators (SSRRs) and double-split ring resonators (DSRRs) in the vertical direction are tailored by reconfiguring the resonator geometries. To design unequal arm lengths for controlling the floating split angle of the resonators and changing their electromagnetic multipole compositions, vertical metamaterials were fabricated using the metal-stress-driven self-folding method. The simulation results well agree with the experimental transmittance and reflectance results and demonstrate the geometry-dependent angle variation of the far-field radiation. Symmetric SSRRs and DSRRs radiate in the vertical and horizontal directions, respectively. With increasing pad shift, the radiation angle of the asymmetric SSRR completely rotates toward the horizontal direction along the ring plane, but the DSRRs can rotate only from 0° to 45° to the horizontal plane. Furthermore, by decomposing the multipoles into their constituents, we show that the directional scattering performance can be verified by manipulating the horizontal and vertical components of the electric dipoles. This novel combination of SSRRs and DSRRs can effectively and efficiently reconfigure the radiation direction in the infrared (IR) region, paving the way for color routers, metasurfaces, and directive IR emitters in compact optical metadevices.

Highly sensitive DS-CSRR based microwave sensor for permittivity measurement of liquids

In this work, a low-cost double split complementary split ring resonator (CSRR) microwave sensor has been designed and fabricated on an FR4 substrate for permittivity characterization of liquids. This modified CSRR structure is proposed to make use of the benefits of the dielectric resonator technique compared to other types of microwave methods. The resonator structure comprises two slits in each of the rings normal to each other while maintaining one slit in each ring along the feed line for maximum excitation of the resonator. The resonator with substrate dimensions of acts like an inductance-capacitance-resistance (LCR) circuit and operates at of the industrial scientific and medical band. Eleven different liquid samples (each with of volume) covering a wide permittivity range of have been used to measure the transmission coefficient using vector network analyzer. In comparison with many recently reported works, the sensitivity of the sensor is found to be higher with average and normalized sensitivity of permittivity and respectively. Fit equations are developed for both real and imaginary parts of permittivity, and using the fit equations the permittivity of three unknown samples are determined with less than error. The sensor adopts a unique orientation of the slits to enhance the E-field intensity for better interaction of the samples with the sensor. A compact form factor, low production cost, future integration possibilities, and high sensitivity are the distinct highlights of the sensor. The sensor promises to be a potential candidate for situations that demands low-cost and highly accurate measurements and may be a good alternative to commercial sensors for dielectric characterization, concentration analysis, and impurity measurement of liquids.

High-Linearity Wireless Passive Temperature Sensor Based on Metamaterial Structure with Rotation-Insensitive Distance-Based Warning Ability.

A wireless passive temperature sensor based on a metamaterial structure is proposed that is capable of measuring the temperature of moving parts. The sensor structure consists of an alumina ceramic substrate with a square metal double split-ring resonator fixed centrally on the ceramic substrate. Since the dielectric constant of the alumina ceramic substrate is temperature sensitive, the resonant frequency of the sensor is altered due to changes in temperature. A wireless antenna is used to detect the change in the resonant frequency of the sensor using a wireless antenna, thereby realizing temperature sensing operation of the sensor. The temperature sensitivity of the sensor is determined to be 205.22 kHz/°C with a strong linear response when tested over the temperature range of 25-135 °C, which is evident from the R2 being 0.995. Additionally, the frequency variation in this sensor is insensitive to the angle of rotation and can be used for temperature measurement of rotating parts. The sensor also has a distance warning functionality, which offers additional safety for the user by providing early warning signals when the heating equipment overheats after operating for extended durations.

Broadband acoustic absorbers based on double split-ring resonators at deep subwavelength scale

We report both experimentally and numerically that a low-frequency acoustic absorber is realized by double split-ring resonators backed with a rigid wall. This absorber leverages the impedance matching and dissipation effect, which arises due to the thermal-viscous loss within the dual channels. As a result, this absorber achieves near-perfect sound absorption (the absorption coefficient α = 0.99) at a subwavelength thickness of around λ/23. By assembling six unit cells with distinct structure parameters to form a supercell, the fractional bandwidth (the ratio of the bandwidth to the center frequency) is increased to 40% with an average α of 0.86. Acoustic experiment results validate this exceptional performance, which is also in agreement with the simulation results. Moreover, by employing the supercell, we create an anechoic room demonstrating broadband sound absorption in a wide range of incident angles while occupying significantly less space than traditional sound-absorbing porous materials. Our double split-ring composite design paves the way for broadband acoustic absorbers at the deep subwavelength scale

TeraHertz wideband cross-polarization conversion metasurface based on double split-ring resonator

This paper presents the design and analysis of a switchable metasurface for wideband cross-polarization conversion in the terahertz (THz) regime. A dual-split ring resonator (DSRR) connected with a narrow metallic strip is used to achieve wideband cross-polar conversion from 2–4.85 THz. Till date, this is the highest reported bandwidth for a THz cross-polarization conversion metasurface. This wideband operation is achieved by exciting the closely spaced resonant frequencies of the DSRR occurring at 2.22 THz, 2.78 THz, 3.96 THz, and 4.68 THz. Additionally, photoconductive silicon is integrated in between the gaps of DSRR for continuous tuning in the operating frequency range. The proposed polarization converter has a compact unit cell size of 0.29 λ0, where λ0 is the free space wavelength at the lowest cut-off frequency. The proposed cross-polarizer achieved excellent polarization conversion ratio (PCR) of ≥ 94% over the entire bandwidth and exhibits wide angular stability up to 45∘. With these advantages, the proposed metasurface has potential applications in THz communication systems, especially in the field of imaging and sensing.

Tunable double split-ring resonator for quantum sensing using nitrogen-vacancy centers in diamond

For quantum sensing based on nitrogen-vacancies (NV) ensembles, microwave antennas can couple the microwave field to the NV center, which leads it to becoming the core of spin manipulation and can directly affect the sensitivity of quantum sensing. The double split-ring resonator is a widely used microwave device for NV ensembles due to the advantages of high radiation efficiency and uniform magnetic field in millimeter-scale areas. But the bandwidth (30 MHz) is quite narrow which limits the application in quantum sensing with NV ensembles. Here, we experimentally achieve continuous tuning of the resonant frequency of the double split-ring resonator by changing the copper sheet position on the edge of the outer ring. The frequency tuning range can reach 80 MHz, up to 2-3 times the bandwidth, which can cover the transition of the electron spin under different magnetic field conditions. The performance of the tunable antenna in the quantum operation of NV centers is verified by optically detected magnetic resonance and Rabi oscillation. This tunable antenna is promising in the fabrication of integrated and arrayed quantum sensors based on NV ensembles.

Broadband and high-efficiency polarization conversion with a nano-kirigami based metasurface

Nano-kirigami metasurfaces have attracted increasing attention due to their ease of three-dimension (3D) nanofabrication, versatile shape transformations, appealing manipulation capabilities and rich potential applications in nanophotonic devices. Through adding an out-of-plane degree of freedom to the double split-ring resonators (DSRR) by using nano-kirigami method, in this work we demonstrate the broadband and high-efficiency linear polarization conversion in the near-infrared wavelength band. Specifically, when the two-dimensional DSRR precursors are transformed into 3D counterparts, a polarization conversion ratio (PCR) of more than 90% is realized in wide spectral range from 1160 to 2030 nm. Furthermore, we demonstrate that the high-performance and broadband PCR can be readily tailored by deliberately deforming the vertical displacement or adjusting the structural parameters. Finally, as a proof-of-concept demonstration, the proposal is successfully verified by adopting the nano-kirigami fabrication method. The studied nano-kirigami based polymorphic DSRR mimic a sequence of discrete bulk optical components with multifunction, thereby eliminating the need for their mutual alignment and opening new possibilities.

Graphene-Based Metasurface Refractive Index Biosensor for Hemoglobin Detection: Machine Learning Assisted Optimization.

Machine learning is the latest approach to optimize the performance of absorbers, sensors, etc. A sensor with behavior prediction using polynomial regression is presented. Three different variations of metasurfaces namely double split-ring resonator, single split ring resonator, split ring resonator with thin wire are analyzed. The proposed design aims to achieve the highest sensitivity by observing different designs and different parameter variation. The highest sensitivity is achieved for double split-ring resonator and single split ring resonator designs. The change in thickness of different parameter affect the absorption and the highest sensitivity is calculated based on these variations. The polynomial regression (PR) model is employed to predict the absorption values for assorted combinations of intermediate wavelength values with angle variation, substrate thickness, substrate length, substrate width, graphene potential, and resonator thickness values. Test Cases R-30 and R-50 are evaluated using R2 score metric to assess the effectiveness of PR model for predicting the values of absorption. R2 score close to 1.0 is achieved for all the experiments at a higher (more than 5) polynomial degree, which proves the prediction efficiency of a regression model. The proposed biosensor designed with a PR model can be applied in biomedical applications for hemoglobin detection.

Microstrip Sensor Based on Ring Resonator Coupled with Double Square Split Ring Resonator for Solid Material Permittivity Characterization

This paper analyzes a microwave resonator sensor based on a square split-ring resonator operating at 5.122 GHz for permittivity characterization of a material under test (MUT). A single-ring square resonator edge (S-SRR) is coupled with several double-split square ring resonators to form the structure (D-SRR). The function of the S-SRR is to generate a resonant at the center frequency, whereas D-SRRs function as sensors, with their resonant frequency being very sensitive to changes in the MUT’s permittivity. In a traditional S-SRR, a gap emerges between the ring and the feed line to improve the Q-factor, but the loss increases as a result of the mismatched coupling of the feed lines. To provide adequate matching, the microstrip feed line is directly connected to the single-ring resonator in this article. The S-SRR’s operation switches from passband to stopband by generating edge coupling with dual D-SRRs located vertically on both sides of the S-SRR. The proposed sensor was designed, fabricated, and tested to effectively identify the dielectric properties of three MUTs (Taconic-TLY5, Rogers 4003C, and FR4) by measuring the microwave sensor’s resonant frequency. When the MUT is applied to the structure, the measured findings indicate a change in resonance frequency. The primary constraint of the sensor is that it can only be modeled for materials with a permittivity ranging from 1.0 to 5.0. The proposed sensors’ acceptable performance was achieved through simulation and measurement in this paper. Although the simulated and measured resonance frequencies have shifted, mathematical models have been developed to minimize the difference and obtain greater accuracy with a sensitivity of 3.27. Hence, resonance sensors offer a mechanism for characterizing the dielectric characteristics of varied permittivity of solid materials.

Design of a metamaterial chipless RFID sensor tag for high temperature

A high temperature sensor based on a metamaterial is proposed as a chipless radio frequency identification sensor tag that can measure temperature wirelessly. The metamaterial, based on a double circular split ring resonator (SRR), is highly frequency selective and has negative permittivity. The double circular SRR is fabricated on the alumina ceramic substrate, which acted as the temperature sensing material. The permittivity of the material varies with the temperature parameter, resulting in a shift of backscattered resonant frequency of the sensor tag. Simulations verify the feasibility of this sensor tag in the microwave band under electromagnetic stimuli. When the temperature increases from 200 to 1000 °C, the resonant frequency monotone decreases from 6.64 to 6.26 GHz with an average sensitivity of 0.475 MHz/°C. The sensor tag has features such as high temperature, being wireless, passive, of comparatively low-cost, and miniature, with diversified application potential, allowing it to compete with other sophisticated temperature devices in terms of performance.

Transmission-type coding metasurface with ultra-broadband polarization conversion

The advent of coding metasurfaces (MSs) has established a bond between electromagnetic scattering and digital control. Given that most of the current coding MSs are based on reflection-type, we investigate a novel transmission-type MS that can achieve ultra-wideband and efficient polarization conversion. A new double diagonal split ring resonator structure is designed to mainly constitute the unit. The 1-bit and 2-bit coding arrays are constructed using the proposed polarization rotation mechanism of the MS unit combined with the dimensional transformation to achieve beam focusing, beam deflection, and beam splitting. Finally, the broadband focusing characteristic of the coding MS is also demonstrated. Numerical simulation results demonstrate that the transmission coefficient of the proposed MS is above 90% in the frequency range of 0.4 to 2 THz, with a relative bandwidth of 133.3%. Asymmetric transmission phenomenon is observed in the range of 0.4 to 2 THz, with coefficients remaining above 80% in all ranges.The proposed coding MS can be used in terahertz polarization converters and unidirectional transmission devices due to its superior polarization conversion performance.

Reconfigurable Split Ring Resonators by MEMS-Driven Geometrical Tuning.

A novel approach for dynamic microwave modulation is proposed in the form of reconfigurable resonant circuits. This result is obtained through the monolithic integration of double split ring resonators (DSRRs) with microelectromechanical actuators (MEMS) for geometrical tuning. Two configurations were analyzed to achieve a controlled deformation of the DSRRs' metamaterial geometry by mutual rotation or extrusion along the azimuthal direction of the two constituent rings. Then, the transfer function was numerically simulated for a reconfigurable MEMS-DSRR hybrid architecture where the DSRR is embedded onto a realistic piezo actuator chip. In this case, a 370 MHz resonance frequency shift was obtained under of a 170 µm extrusion driven by a DC voltage. These characteristics in combination with a high Q factor and dimensions compatible with standard CMOS manufacturing techniques provide a step forward for the production of devices with applications in multiband telecommunications and wireless power transfer and in the IoT field.

Broadband electrically tunable linear polarization converter based on a graphene metasurface.

In this study, a broadband tunable reflective graphene-based linear polarization converter (GLPC) is proposed based on the graphene-ionic liquid-ITO structure (GIIS) integrated with a periodic double split ring resonator (DSRR) in the millimeter-wave regime. The tuning characteristic of the designed GLPC is analyzed using full-wave simulations and the equivalent circuit model method (ECM), which is based on multi-section transmission lines. There is a good agreement between ECM and simulation results. A comprehensive physical mechanism for the proposed broadband GLPC is then achieved by analyzing the surface current distributions. After manufacturing, the GLPC prototype's co- and cross-polarized reflection coefficients were measured using various bias voltages. The reflectivity can be controlled from -4.5 to -20 dB by changing the bias voltage in the range of +1.1 to -3.3 V. The designed GLPC can provide a tunable polarization conversion within the frequency range of 15.5∼35 GHz and shows a more than 75% conversion efficiency. The results of the simulation and the measurement are also in good agreement. The designed GLPC has potential applications in radar cross-section reduction, antenna design, and stealth technology by reconfiguring its polarized reflection characteristic dynamically.