Symmetric Resonator Research Articles

Eigenmode hybridization enables lattice-induced transparency in symmetric terahertz metasurfaces for slow light applications

Traditional lattice-induced transparency demonstrations are activated by varying the meta-atom lattice constant such that the plasmonic and lattice modes interfere. Here we report on the observation of enhanced coupling between two eigenmodes (first- and second-order) by varying the lattice parameter in a symmetric split ring resonator design. The higher-order quasi-dark mode blueshifts, introducing strong coupling with the fundamental bright mode for periods above 345 μm. Numerical simulations are verified experimentally and supplemented with a two-oscillator model showing good agreement. Furthermore, larger positive group delay values are achieved in the vicinity of the transparency window with minimal absorption, indicating a strong potential for slow light applications.

Multi-functional terahertz metamaterial using symmetrical and asymmetrical electric split-ring resonator

Abstract We present the electromagnetic coupling effects in four types of electric split-ring resonators (eSRRs). These four designs of eSRRs are based on SRR tailored with single-, dual-, triple-, and quad-split, respectively. The near-field electromagnetic coupling responses indicate the resonance caused from the inductive-capacitive (LC) resonance between eSRRs. According to the patterns of eSRR are symmetrical or asymmetrical configurations, these eSRRs exhibit polarization-dependence, polarization-independence, resonant frequency shifting, resonant intensity modulation, and resonant switching characteristics, respectively. To increase the flexibility and applicability of eSRRs, two patterned eSRR layers are designed on elastic substrate for the enhancement of the resonant tunability. The designs of eSRRs open an avenue to a new direction for future optical applications, which offer significant promise in flexible electronics applications. This work provides future tunable THz designs based on flexible actuation mechanism to deform the geometrical dimensions between eSRRs microstructures.

Research and application of weak fault diagnosis method based on asymmetric potential stochastic resonance

Because fault characteristics are often difficult to extract from a strong noise background, it is essential for mechanical fault diagnosis to extract a weak characteristic signal with a very small signal-to-noise ratio from a noisy interference. Therefore, this paper proposes a new method for diagnosing weak faults in asymmetric potential stochastic resonance. Compared with the existing methods, the asymmetric potential stochastic resonance method not only has characteristics common to the symmetric potential stochastic resonance, but can also change the inclination of the barrier and slope of the wall to obtain a better model structure. The proposed method solves the local adjustment problem of the existing method from the perspective of potential structure and optimizes the asymmetric system shape to better target frequency detection during much interference from noise. After simulation, a bearing failure test, and rolling mill gearbox bearing failure experiments, we concluded that the asymmetric potential stochastic resonance detection technology can effectively identify faults. Compared with the symmetric potential stochastic resonance method, the proposed method has better recognition.

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.

A D-type fiber based symmetrical long-range surface plasmon resonance sensor with high quality factor

A D-type fiber based symmetrical long-range surface plasmon resonance (sLRSPR) sensor with high quality factor (Q-F) as high as 107.52 RIU−1 was proposed and experimentally demonstrated. The sensing structure of the proposed sensor consisted of fiber/dielectric buffer layer (DBL)/Au film/DBL/analyte, and the DBLs on both sides of the Au film in the sLRSPR sensor were identical, which greatly increased the permittivity matching degree between the analyte and the DBL near the D-type fiber, and reduced the loss of long-range surface plasmon polaritons. For LRSPR sensor, the closer the permittivities of DBL and analyte on both sides of metal film are, the easier the LRSPR is to stimulate, and thus the proposed sensor possessed higher sensitivity and higher detection accuracy. The transfer matrix method supported by the finite-difference beam propagation method and the finite element analysis was employed to optimize the sensor parameters for the first time. The refractive index sensing performance of the conventional SPR (cSPR) sensor, the conventional LRSPR (cLRSPR) sensor, and the sLRSPR sensor with optimal parameters were systematically researched by simulation and in-depth experiment. The results suggested that the sensing performance of the sLRSPR sensor was better than that of the other two sensors. This paper provided a meaningful advancement for designing an optical fiber SPR sensor with remarkable performance to measure biomass.

Sensing Gases by the Pole Effect of Parity-Time Symmetric Coupled Resonators

The pole is the unique phenomena in the parity-time (PT) symmetry structure. To explore the application of the pole effect, a PT-symmetry resonator coupling system is designed as a gas sensor. The large transmittance and reflectance near the pole are found extraordinary sensitive to the refractive index of the polluted air in the system. Through measuring the reflectance, the refractive index of the polluted air and the concentration of gas in the air can be detected. The sensor has an extraordinary sensitivity in detecting the gases with low concentration. The maximum sensitivities $\Delta R/R$ for the methane, acetylene, and ethane are 0.112, 0.190, and 0.282, respectively. The limitation of detectable concentration change is 1/1500 for methane with the photodetector that can sense the relative change rate of the reflectance of 10−3.

The microstrop step discontinuity analysis by transverse resonance technique: method of boundary value problem algebraization

The two-dimensional eigenfunctions of the magnetic and electric vector potentials are constructed in the form of their expansion in series of Chebyshev orthogonal polynomials of 1st and 2nd kind to describe the current density in a strip transmission line with a step discontinuity of finite length. The solving boundary value problems algorithms for the resonant frequencies of a symmetric microstrip resonator with a capacitive section in it are developed and investigated on convergence. The account of the field behavior on thin edge in a nonuniform strip line provides the fast convergence of algorithm and small orders of solvable linear algebraic equations system. As examples of application, the transverse resonance method was used to calculate the scattering characteristics on 2-plane symmetric discontinuities consisting of a capacitive section of a microstrip line and slot resonators of complex shape in its ground plane.

Infrared dim target detection method based on the fuzzy accurate updating symmetric adaptive resonance theory

Motivated by the human visual system, we propose an infrared dim target detection method that is based on a fuzzy accurate updating symmetric adaptive resonance theory network. From the bottom-up perspective, the regions of interest (ROIs) are extracted using a difference of Gaussians at multiple scales and our designed ROI model in a saliency map. From the top-down perspective, five feature categories are extracted using the ROI model, which are used to train the proposed Fuzzy AUSART network. The well-trained network realizes the true identification of all ROI candidates. The results of the receiver operating characteristic (ROC) curves verify that the proposed method can better adapt to different circumstances and targets in our experiment. The average detection accuracy of the Fuzzy AUSART is improved by 15.4%, and the average F1 index of the proposed method is higher than six typical comparison methods by more than a factor of 2.48.

Terahertz toroidal metamaterial with tunable properties.

We present a tunable metamodulator to work at terahertz frequencies by employing the dependency of toroidal dipolar resonance on the conductivity of vanadium dioxide. Numerical results show that toroidal dipolar resonance in the proposed planar structure can be observed around 0.288 THz in transmission spectrum. From the distribution of the anti-phase current flowing in the symmetric split ring resonator, the formation of toroidal dipole is validated. Our design may have potential applications in advanced terahertz devices, such as filter, plasmonic sensor, and fast switch.

Active control of elastic metamaterials consisting of symmetric double Helmholtz resonator cavities

Wave invisibility has quite special meaning on marine vehicles under water, which encourages people to search effective methods for a long history. Initiated by this point, we propose a new class of active elastic metamaterials and a cloaking design consisting of double Helmholtz cavities. By changing external voltage with different piezoelectric diaphragm stiffness, this structure shows a controllable effective bulk modulus in which a negative value appears over a wide frequency range. This configuration with double active cavities provides better tunable abilities to achieve the effective bulk modulus than that with a single cavity. In order to design a multilayered cloak and a non-blind cloak, the coupling of the adjacent cavity cells is considered and the control strategy for the periodic cavities with active Helmholtz resonators is developed. The parameters of the multilayered acoustic cloak can be obtained by the coordinate transformation method and the corresponding effective medium theory. This action can be implemented by the active control on each unit cell to drive the distribution of effective bulk modulus. These characteristics with a tunable effective bulk modulus at a very wide frequency range are significant to control elastic wave propagation.

Chaotic dynamics and optical power saturation in parity–time (PT) symmetric double-ring resonator

In this work, we report emergence of saturation and chaotic spiking of optical power in a double-ring resonator with balanced loss and gain, obeying the so-called parity–time symmetry. We have modeled the system using a discrete-time iterative equation known as the Ikeda map. In the linear regime, evolution of optical power in the system shows power saturation behavior below the PT threshold and exponential blowup above the PT threshold. We found that in the unbroken PT regime, optical power saturation occurs owing to the existence of stable stationary states, which lies on the surface of four-dimensional hypersphere. Inclusion of Kerr nonlinearity into our model leads to the emergence of a stable, chaotic and divergent region in the parameter basin for period-1 cycle. A closer inspection into the system shows us that the largest Lyapunov exponent blows up in the divergent region. It is found that the existence of high nonnegative largest Lyapunov exponent causes chaotic spiking of optical power in the resonators.

MEMS Gyroscope With Concentrated Springs Suspensions Demonstrating Single Digit Frequency Split and Temperature Robustness

We report on a new design approach for X-Y symmetric resonator, emphasizing the increase in symmetry by localization of the device anchors. The resonator is mechanized as a z-axis rate gyroscope (RG), and the concept is compatible with the rate-integrating gyroscope mechanization. Our approach is based on strategically placing the critical mechanical elements at the center of the resonator structure, to mitigate the effect of fabrication imperfections across the device. We experimentally demonstrated that the design yields a sub-Hz frequency separation between operational modes, which is attributed to the introduced design approach. The high symmetry of the device led to a temperature stability of 50 mHz over 130 °C temperature range. A ring down test demonstrated the Q -factor greater than 330 K. The thermal stability and preliminary characterization results of the gyro in-run stability are presented. [2017-0177]

Signal Sensitivity Enhancement of High-Spatial-Resolution MR Imaging with a Concatenated Cylindrical Parametric RF-Resonator.

Phased array MRI coils can increase sensitivity of superficial tissues owing to their proximity to the detection region. Deep-lying tissues, on the other hand, do not benefit to the same degree. Here we investigate the use of a localized cylindrically symmetric quadruple frequency resonator concatenated with a double frequency resonator to increase the longitudinal field-of-view (FOV) without compromising the spatial-resolution and detection sensitivity. These concatenated array coils work on the principle of a parametric amplification to provide wireless amplification of the locally detected NMR signal prior to inductively coupling the coil to an external pick-up loop with connection to the system receiver. When both the detectors are activated together, the effective range of both overlay to create a larger FOV enabling better identification of detectable regions. Furthermore, the in-vivo test of the concatenated detector provides a worst-case 5-fold SNR gain in regions separated from the cylindrical surface larger than its own diameter. This proposed approach of concatenated detector realization can be individually activated and manipulated to enlarge the sensitivity-enhanced region without sacrificing their individual performance. Compared to double frequency detectors, quadruple frequency detectors offer more flexibility in the choice of detector dimension, enabling multi-element concatenation over an extended FOV.

Graphene based polarization independent Fano resonance at terahertz for tunable sensing at nanoscale

A two-dimensional metamaterial structure consisting of polyimide layer covered by a square disk of monolayer graphene and the gold symmetrical split resonance ring is proposed and investigated. Our simulations indicate that the Fano resonance mode in the terahertz range can be generated by this metamaterial structure, and also utilized for nanoscale sensing. The maximum frequency shift is 1671.61 GHz, and the frequency sensitivity is 1.18 THz/RIU for 2-nm-thick analyte. Furthermore, by adjusting the Fermi level of graphene, the resonance frequency can be tuned actively. Different from the Fano resonance excited by asymmetric structure, the proposed structure is polarization-insensitive and can perform well with both TE and TM waves

Enhanced absorption of monolayer molybdenum disulfide (MoS2) using nanostructures with symmetrical cross resonator in the visible ranges

In order to enhance the absorption of monolayer molybdenum disulfide (MoS2), a novel nanostructure with symmetrical cross resonator based on MoS2 in the visible wavelength ranges has been proposed. At a resonant wavelength of 623 nm, the absorption of monolayer MoS2 in the absorption structure is as high as 82%, much higher than the bare MoS2 in the air. The electric field around monolayer MoS2 is enhanced by the guided mode resonance, thereby enhancing the absorption of monolayer MoS2 in the structure. The relevant parameters of the proposed structure are adjusted to achieve the tunability of the resonant wavelength in the visible ranges and the high-efficiency absorption of monolayer MoS2 in the structure, which is of great significance for the applications of MoS2-based optoelectronic devices.

A Novel Fiber-Based Symmetrical Long-Range Surface Plasmon Resonance Biosensor With High Quality Factor and Temperature Self-Reference

A novel wavelength modulated optical fiber-based symmetrical long-range surface plasmon resonance (sLRSPR) biosensor with high quality factor (Q-F) of 56.70 RIU−1 and temperature self-reference was proposed and demonstrated. The multilayered architecture of the sLRSPR biosensor consisted of cladding/dielectric-buffer-layer (DBL)/Au-nanofilm/DBL/analyte, and the DBLs on both sides of the Au-nanofilm were identical, which greatly increased the matching degree of the permittivities of analyte and the DBL near cladding and reduced the loss of long-range surface plasmon-polaritons. Therefore, the sLRSPR sensor displayed excellent sensing performance, and its Q-F was 3.27-folds higher than that of the conventional SPR sensor. Furthermore, the sLRSPR sensor was employed as a biosensor for the measurement of average refractive index (RI) of cell, and the temperature-sensitive optical adsorption characteristic of the DBL was utilized to provide temperature self-reference for the RI measurement. The sLRSPR biosensor realized simultaneous measurement of RI and temperature at the exactly same location, which can eliminate the measurement error introduced by temperature to RI measurement. The sLRSPR biosensor proposed in this paper possessed higher detection precision and presented greatly promising application prospects in the field of biochemistry.

Resonant acoustic scattering by two spherical bubbles.

The mutual interaction between two close bubbles in an acoustic field is studied. This interaction is modeled in the linear framework of the multiple scattering theory using spherical harmonics expansions and the addition theorem. In order to deal with small as well as large bubbles, viscous dissipation in the liquid, thermal dissipation in the gas, and surface tension are taken into account in the calculations of the scattering coefficients of a unique bubble. Under the assumption of the long wavelengths, the scattering coefficient of the monopolar mode is linked to the one obtained by using the Rayleigh-Plesset equation. The exact characteristic equation providing the symmetric and antisymmetric resonances of the two bubbles is established. Numerical results show that a great number of modes of vibration is required to describe the acoustic field around the bubbles. Moreover, whatever the spacing between two identical bubbles, the scattering cross section has a maximum value at the frequency of the symmetric mode while the antisymmetric mode is not detected. However, the strengthening of the scattering observed close to the symmetric resonance frequency is clearly due to the presence of the antisymmetric mode.

Dual Notch Microwave Sensors Based on Complementary Metamaterial Resonators

In this paper, three dual notch microwave sensors are presented based on a microstrip transmission line and complementary metamaterial resonators. The main aim of this paper is to compare the constitutive parameters and sensitivity of all three dual notch sensors which are based on complementary symmetric split ring resonator (CS-SRR), complementary asymmetric split ring resonator (CAS-SRR) and complementary bisymmetric split ring resonator (CBS-SRR). The main motivation beyond the presented work is to use dual notches to estimate the relative permittivity of material under test (MUT). Electromagnetic simulation elucidates the origin of dual mode resonance of all the three resonators. Sensitivity analysis is performed on each sensor by using fifteen MUTs with relative permittivity ranges from 1.006 to 16.5 and constant dimensions 10 mm × 10 mm × 1 mm. To verify the concept, a sensor is fabricated and its response is measured using a vector network analyzer (AV3672). Using curve fitting technique the shift in the resonance frequencies of the fabricated sensor due to interaction with MUT is presented as a function of permittivity. Simulated, measured and formulated results are in good agreement with each other.

基于硅各向同性腐蚀工艺的三维曲面壳体微谐振器制备技术

基于硅各向同性腐蚀工艺的三维曲面壳体微谐振器制备技术

Rhythmic modulation of thalamic oscillations depends on intrinsic cellular dynamics

Objective. Rhythmic brain stimulation has emerged as a powerful tool to modulate cognition and to target pathological oscillations related to neurological and psychiatric disorders. However, we lack a systematic understanding of how periodic stimulation interacts with endogenous neural activity as a function of the brain state and target. Approach. To address this critical issue, we applied periodic stimulation to a unified biophysical thalamic network model that generates multiple distinct oscillations, and examined thoroughly the impact of rhythmic stimulation on different oscillatory states. Main results. We found that rhythmic perturbation induces four basic response mechanisms: entrainment, acceleration, resonance and suppression. Importantly, the appearance and expression of these mechanisms depend highly on the intrinsic cellular dynamics in each state. Specifically, the low-threshold bursting of thalamocortical cells (TCs) in delta (δ) oscillation renders the network relatively insensitive to entrainment; the high-threshold bursting of TCs in alpha (α) oscillation leads to widespread oscillation suppression while the tonic spiking of TC cells in gamma (γ) oscillation results in prominent entrainment and resonance. In addition, we observed entrainment discontinuity during α oscillation that is mediated by firing pattern switching of high-threshold bursting TC cells. Furthermore, we demonstrate that direct excitatory stimulation of the lateral geniculate nucleus (LGN) entrains thalamic oscillations via an asymmetric Arnold tongue that favors higher frequency entrainment and resonance, while stimulation of the inhibitory circuit, the reticular nucleus, induces much weaker and more symmetric entrainment and resonance. These results support the notion that rhythmic stimulation engages brain oscillations in a state- and target-dependent manner. Significance. Overall, our study provides, for the first time, insights into how the biophysics of thalamic oscillations guide the emergence of complex, state-dependent mechanisms of target engagement, which can be leveraged for the future rational design of novel therapeutic stimulation modalities.