Identical Resonators Research Articles

Compact Multiple-Way Power-Dividing Network with Bandpass-Filtering Response Using Spiral Resonators

ABSTRACTA new type of multiple-way out-of-phase power-dividing network with bandpass-filtering response using spiral resonators is proposed. The basic structure unit is a compact two-way out-of-phase power divider with bandpass-filtering response. The introduction of two identical spiral-type resonators can generate transmission zeros in the lower or upper stopband to implement the bandpass-filtering function. Impedance matching and out-of-phase performance are analyzed by using the even- and odd-mode method based on four-port network theory. A four-way out-of-phase power-dividing network with bandpass-filtering response is constructed and designed according to the basic two-way out-of-phase power-dividing structure. The simulated and measured results of the fabricated out-of-phase bandpass-filtering power-dividing network demonstrate the reasonable performance of impedance matching, amplitude balance, and bandpass-filtering function.

Vacuum Packaged Low-Power Resonant MEMS Strain Sensor

This paper describes a technical approach toward the realization of a low-power temperature-compensated micromachined resonant strain sensor. The sensor design is based on two identical and orthogonally-oriented resonators where the differential frequency is utilized to provide an output proportional to the applied strain with temperature compensation achieved to first order. Interface circuits comprising of two front-end oscillators, a mixer, and low-pass filter are designed and fabricated in a standard 0.35- $\mu \text{m}$ CMOS process. The characterized devices demonstrate a scale factor of 2.8 Hz/ $\mu \varepsilon $ over a strain range of 1000 $\mu \varepsilon $ with excellent linearity over the measurement range. The compensated frequency drift due to temperature is reduced to 4% of the uncompensated value through this scheme. The total continuous power consumption of the strain sensor is 3 $\mu \text{W}$ from a 1.2 V supply. This low power implementation is essential to enable battery-powered or energy harvesting enabled monitoring applications. [2015-0328]

Accessing the High‐Q Dark Plasmonic Fano Resonances in Superconductor Metasurfaces

Superconducting metamaterials at terahertz frequencies has provided a platform for designing switchable plasmonic metamaterial devices. However, since metals at terahertz frequencies are excellent conductors, the superior role of superconductors in designing low‐loss, high quality factor metamaterials remains unclear. In this work, a low asymmetry Fano resonant split‐ring‐resonator is considered in which a regime of extremely low radiative loss is identified where the high temperature yttrium barium copper oxide superconductor meta‐atom supports a sharp high quality factor Fano resonance while an identical metallic resonator does not show the resonance behavior. The radiative and the nonradiative losses are comparable in low asymmetry Fano resonant meta‐atoms. The observation of high quality factor Fano resonance behavior clearly establishes the utility of superconductors over metals in designing lower loss plasmonic metamaterials at terahertz frequencies that may have multifunctional applications in areas that require strong light–matter interactions.

Multiband High-Order Bandstop 3-D Frequency-Selective Structures

A general methodology for the design of multiband high-order three-dimensional (3-D) frequency-selective structures (FSSs) is proposed. The methodology is based on employing multiple resonators inside a unit cell (UC) to obtain a multiband response, and by controlling the coupling between identical resonators, a high-order filtering performance is achieved. This provides more transmission zeros in the operating bands, which lead to improved bandwidth and high selectivity. Detailed analysis for the coupling between identical resonators is provided as well as equivalent circuit models to explain the operating principle. Three structures are designed, fabricated, and measured to verify the proposed methodology. The first structure is a triband second-order FSS with center frequencies at 9.6, 13.4, and 17.5 GHz and their $-3-\text{dB}$ fractional bandwidths of 13.5%, 8.5%, and 12.6%, respectively. The second structure is designed to have a dual-band third-order response with center frequencies at 13.2 and 19.6 GHz and their $-3\text{-}{\rm dB}$ fractional bandwidths of 16% and 13.3%, respectively. The last structure is designed to exhibit a dual-band second-order response under both TE and TM polarizations with center frequencies at 11.2 and 13.8 GHz and $-3\text{-}{\rm dB}$ fractional bandwidths of 5.5% and 4%, respectively.

Compact resonator on leather for nonradiative inductive power transfer and far‐field data links

AbstractIn this paper, a wearable resonator suitable to be used for both power and data transmission is presented. The basic element is a complementary split ring resonator that has been optimized to operate both as a dipole‐like antenna at 2.45 GHz and as the receiver of a resonant energy link operating at 915 MHz when coupled with an identical external resonator connected to a power source. Experimental data referring to a prototype fabricated by using a conductive adhesive fabric on a leather substrate are reported and discussed. With regard to the wireless resonant energy link (WREL), it is demonstrated that at 915 MHz, the RF‐to‐RF power transfer efficiency of the link is approximately 78.1%. As for the performance obtained when the resonator is used as an antenna, a gain of approximately −0.43 dB was obtained. Additionally, the performance of the proposed link when connected to a Power Management Unit (PMU) that converts the radio frequency (RF) energy received by the wearable resonator into DC energy that can be directly used for recharging a thin‐film battery was also investigated. Experimental tests were performed in order to evaluate both the total efficiency of the wireless charger (i.e., the WREL link connected to the PMU) and the time necessary to recharge a THINERGY MEC201 battery. The obtained results demonstrate the feasibility of using the proposed WREL for implementing a battery charger; in particular, by providing an input power higher than 8 dBm, the time necessary to recharge the considered thin‐film battery is shorter than 38 min.

Wave Propagation in Sandwich Structures With Multiresonators

A new sandwich beam with embedded multiresonators is presented. Two continuum Timoshenko beam models are adopted for modeling sandwich beams. Numerical results show that multiple resonators can lead to multiple resonant-type bandgaps with remarkable wave attenuation. The effective mass is found to become negative for frequencies in the bandgaps where the wave is greatly attenuated. With two identical resonators connected in parallel, only one single bandgap can be found. If two resonators with equal masses and springs are connected in series, the central frequency of the second bandgap is approximated twice of the central frequency of the first gap. For the beam with series-connected resonators, a simple two degrees-of-freedom system is proposed and used for predicting the initial frequencies of the bandgaps while for the beam with resonators in parallel, two separate single degree-of-freedom systems are introduced.

Influence of Sugar Palm Ash Fraction and Resonator Configuration on Acoustic Absorption Performance of Expose Brick

<span>Sound absorption performance optimization of expose brick has been conducted in associated with <span>the fraction of sugar palm ash in its raw material and configuration of Helmholtz resonators inside <span>the brick structure. The testing was conducted experimentally refer to ASTM E-1050-98 standard <span>procedure. In this case there are three variations sugar palm ash fractions of 0%, 5%, and 10%, as <span>well as two array resonator configurations. The results showed that the brick with fraction of 10% <span>sugar palm ash has the best sound absorption performance. As for the configuration of array <span>identical Helmholtz resonator giving better performance improvement at low frequency span than <span>complex resonator structure with coupled cavity where the best performance occur on(376-488) <span>Hz frequency range with the absorption coefficient α of 0.54.</span></span></span></span></span></span></span></span><br /></span>

Suppression of bending waves in a beam using resonators with different separation lengths.

This work is concerned with the suppression of a bending wave in a beam using resonators. Particular focus is put on the separation length between resonators. It is demonstrated that, for a beam with identical resonators attached at equal intervals, the bending wave transmission efficiency varies with respect to the separation length. The phenomena and the underlying physics are investigated by resorting to a simple beam model having two resonators resting on it. The two resonators are coupled over the segment through various bending wave components, comprising both propagating waves and evanescent waves, generated at the resonator locations where the beam encounters impedance discontinuities. The separation length, specifying the phase change of the propagating waves and the amplitude decay of the evanescent waves travelling from one resonator to the other, is thereby the parameter determining the extent to which the resonators would be coupled and the degree of the power that is transmitted. Results show, qualitatively, the difference in the working mechanism of the resonators in different separation length regions, with criteria being defined to distinguish those regions. Particularly, in the intermediate separation region, the evanescent waves are shown to play an important role in the coupling and are responsible for transmitting power, comparable with that transmitted by propagating waves, to the far field.

Origin of strain-induced resonances in flexible terahertz metamaterials**Project supported by the National Natural Science Foundation of China (Grant Nos. 11204146 and 61574144), the Ningbo Key Laboratory of Silicon and Organic Thin Film Optoelectronic Technologies, China, the Program for Ningbo Municipal Science and Technology Innovative Research Team, China (Grant No. 2015B11002), and the K. C. Wong Magna Foundation in Ningbo University,

Two types of flexible terahertz metamaterials were fabricated on polyethylene naphthalate (PEN) substrates. The unit cell of one type consists of two identical split-ring resonators (SRRs) that are arranged face-to-face (i.e., FlexMetaF); the unit cell of the other type has nothing different but is arranged back-to-back (i.e., FlexMetaB). FlexMetaF and FlexMetaB illustrate the similar transmission dips under zero strain because the excitation of fundamental inductive–capacitive (LC) resonance is mainly dependent on the geometric structure of individual SRR. However, if a gradually variant strain is applied to bend FlexMetaF and FlexMetaB, the new resonant peaks appear: in the case of FlexMetaF, the peaks are located at the lower frequencies; in the case of FlexMetaB, the peaks appear at the frequencies adjacent to the LC resonance. The origin and evolution of strain-induced resonances are studied. The origin is ascribed to the detuning effect and the different responses to strain from FlexMetaF and FlexMetaB are associated with the coupling effect. These findings may improve the understanding on flexible terahertz metamaterials and benefit their applications in flexible or curved devices.

Tunable high quality factor in two multimode plasmonic stubs waveguide.

We numerically investigate the optical characteristics of a metal-dielectric-metal (MDM) waveguide side-coupled with two identical multimode stub resonators. Double plasmon-induced transparency (PIT) peaks with narrow full width at half maximum (FWHM) and high quality factor (Q-factor) can be observed in this structure. The Q-factors of PIT peaks in two stub resonators system are larger than those in single stub resonator system. A multimode coupled-radiation oscillator theory (MC-ROT), which is derived from ROT, is proposed to analyze the spectral response in the multimode system for the first time. The analytical results are confirmed by the finite-difference time-domain (FDTD) simulation results. We can also find that the Q-factors of the two PIT peaks have an opposite evolution tendency with the change of the stubs parameters and the maximum can reach to 427. These results may provide some applications for ultrasensitive sensors, switches and efficient filters.

High-Selectivity Bandpass Frequency-Selective Surface in Terahertz Band

A terahertz (THz) bandpass frequency-selective surface (FSS) with high selectivity is proposed in this work. The three-layered FSS filter consists of identical tripole resonators located on the top and bottom layers and rectangular coupling apertures etched on a conducting plane in between. Multiple signal paths exist between the top and bottom resonators through the coupling apertures. Therefore, this aperture-coupled resonator (ACR) structure exhibits a narrow bandpass response, and two transmission zeros appear near the skirts of the passband. These zero points considerably improve the frequency selectivity and suppress the sidebands of the FSS. For demonstration, a microfabrication process was used to realize an ACR FSS at 850 GHz. The frequency performance of the ACR FSS in terms of insertion loss is investigated numerically and experimentally. The measured transmission responses at normal incidence based on time-domain as well as frequency-domain measurements agree well with the simulated one, thus verifying the proposed design. Furthermore, the frequency-domain measurement reveals that the FSS response remains stable at various incident angles for both TE and TM polarizations.

Acoustic-Wave-Lumped-Element-Resonator Filters With Equi-Ripple Absorptive Stopbands

Acoustic-wave-lumped-element-resonator (AWLR)-based absorptive bandstop filters (ABSFs) with enlarged-bandwidth (BW) equi-ripple stopbands are presented. They are based on reflection-type architectures whose reflective loads are shaped by $N$ identical series-cascaded AWLRs and $N$ static impedance inverters each. In this manner, equi-ripple stopbands whose BW is no longer limited by the electromechanical coupling coefficient $(k_{t}^{2})$ of the acoustic-wave (AW) resonator are obtained through the distribution of $2N$ transmission zeros (TZs). In contrast to conventional ABSF cascades, fewer inverters and identical AW resonators are employed. This results in benefits in terms of lower insertion loss (IL), reduced size, and higher fabrication robustness. A continuous-type tunable-isolation (IS) and BW-control mechanism by means of variable resonator resistance is reported as a novel contribution. Two-, four-, and six-TZ 418 MHz AWLR-based ABSF prototypes with low passband IL (0.96–1.14 dB), large levels of IS (up to 70 dB), and stopband BWs in the range of 0.03–0.11 MHz were manufactured and characterized as proof-of-concept demonstrators. Reconfigurable prototypes with variable levels of IS between 17–65 dB and BW tuning ratio of 1.33:1 were also measured.

Haldane quantum Hall effect for light in a dynamically modulated array of resonators

Topological insulators have attracted abundant attention for a variety of reasons -- notably, the possibility for lossless energy transport through edge states `protected' against disorder. Topological effects like the Quantum Hall state can be induced through a gauge field, which is however hard to create in practice, especially for charge-neutral particles. One way to induce an effective gauge potential is through a dynamic, time-periodic modulation of the lattice confining such particles. In this way, the Haldane Quantum Hall effect was recently observed in a cold atom system. Here, we show how this same effect can be induced for light confined to a lattice of identical optical resonators, using an on-site modulation of the resonant frequencies. We further demonstrate the existence of one-directional edge states immune to back-scattering losses, and discuss the possibilities for a practical implementation, which would enable slow-light devices of unprecedented quality.

Active Control of Electromagnetically Induced Transparency Analog in Terahertz MEMS Metamaterial

1 wileyonlinelibrary.com C o m m u n iC a io n and their possible applications. The ultimate form of active manipulation of EIT phenomenon will be when all three primary parameters are controlled independently. The independent control of individual resonators demands for the controllability at unit cell level, and conventional approaches such as optical pumping of photoconductive elements or thermally controlled superconductor are restricted to provide only global control. Recently, microelectromechanical systems (MEMS) based tunable metamaterials have been reported to achieve controllability at unit cell level, along with the added advantage of being electrically controlled, miniaturized size and enhanced electrooptic performance. The versatility of MEMS design has enabled active manipulation of numerous THz properties such as magnetic resonance,[19–22] electrical resonance,[23–25] anisotropy,[26] broadband response,[27] isotropic resonance switching[28] multiresonance switching,[29–31] and coupling strength between resonators.[32] The enhanced controllability and direct integration of MEMS actuators into metamaterial unit cell geometry is an ideal fit for the realization of selective control of coupled mode resonators. In this Communication, reconfigurable metamaterial with independently controlled bright and dark mode resonators is proposed for advanced manipulation of the classical analog of EIT and slow light effects in THz spectral region. The active control of bright mode resonator enables modulation of EIT intensity, while the tuning of dark mode resonance causes the EIT peak to tune in frequency. Furthermore, simultaneous switching of bright and dark mode resonators results in dynamic switching of the system between coupled and uncoupled states. The proposed approach of selective reconfiguration can be scaled for multiresonator systems, which can be coupled either through inductive, capacitive, or conductive means. The metamaterial consists of 80 × 80 periodic array of cut wire resonator (CWR) with closely placed split ring resonators (SRRs), as shown in Figure 1 and Figure 2. The periodicity of unit cell is 100 μm along both axial directions. The CWR has length, lC = 60 μm and width, wC = 5 μm, respectively. The SRRs have a base length, bS = 30 μm, side length, lS = 20 μm, and split gap, gS = 4 μm. The SRRs are placed at a distance of S = 2 μm from the CWR. When the polarization of the excitation field is along the CWR arm, the dipole mode resonance of the CWR will be the bright mode and the inductive-capacitive (LC) mode of SRR resonance acts as the dark mode. Thus for the incident THz polarization, the direct excitation of the bright mode induces image charges on the nearby SRRs through nearfield inductive coupling, thereby exciting the LC resonance of the SRRs. These bright-dark resonances have contrasting line widths with identical resonance frequencies and under a strong coupling regime they experience an EIT-type of interference that gives rise to a sharp transmission peak. Thus, through Active Control of Electromagnetically Induced Transparency Analog in Terahertz MEMS Metamaterial

Acoustic transmission from a single crystal layer of nonlinear resonators in a soft elastic matrix

Ultrasound transmission measurements of a single crystal layer of identical nonlinear resonators are reported for frequencies under 1 MHz. The resonators are spherical gas-filled cavities embedded in a soft elastic matrix. The cavities are formed by injection of gas through a capillary tube in a polymer solution right before it cures. Sample characteristics such as the size or the spacing between the cavities are adjusted by varying the injection parameters. Typical size for the cavities ranges from 100 μm to 1 mm. The sample is immersed in water where transmission measurements are conducted. As allowed by acoustic transducer, amplitude and phase of the wave is measured in transmission as a function of the frequency and the amplitude of the initial incident pulse.

Asymmetric optical transmission in an optomechanical array

Optical cavity combining a mechanical degree of freedom provides a unique platform to implement information transmission and processing via optomechanical effects, and introduces a strong link between nanophotonics and nanomechanics. Here, we study the optical property of a cascaded optomechanical array, which consists of two or more optomechanical systems. We find that the steady states of the optomechanical array have algebraic duality symmetry for the case of two identical optomechanical resonators, which is exactly the embodiment of the spatial symmetry and leads to symmetric optical transmission. Breaking of the algebraic duality symmetry gives rise to different behaviors between the forward and the backward transmission, which can be remarkable under low input power. Our results may have potential application for achieving high precision measurement and on-chip manipulation of light propagation.

Test of a virtual cylindrical acoustic resonator for determining the Boltzmann constant

We report progress toward determining the Boltzmann constant kB using the concept of a virtual acoustic resonator, a hypothetical resonator that is mathematically equivalent to a cylindrical cavity with periodic boundary conditions. We derived the virtual resonator by combining the measured frequencies of the longitudinal acoustic modes of two argon-filled, cylindrical cavity resonators in such a way to minimize the effects of the cavities’ ends, including transducers and ducts attached to the ends. The cavities had lengths of 80 mm and 160 mm and were operated in their longitudinal (ℓ,0,0) modes. We explored virtual resonators that combine modes of the two resonators that have nearly the same frequencies. The virtual resonator formed from the (2,0,0) mode of the 80 mm resonator combined with the (4,0,0) mode of the 160 mm resonator yielded a value for kB that is, fractionally, only (0.2 ± 1.5) × 10−6 larger than the 2010 CODATA-recommended value of kB. (The estimated uncertainty is one standard uncertainty corresponding to a 68% confidence level.) The same virtual resonator yielded values of the pressure derivatives of the speed of sound c in argon, (∂c2/∂p)T and (∂c2/∂p2)T, that differed from literature values by 1% and 2%, respectively. By comparison, when each cavity was considered separately, the values of kB, (∂c2/∂p)T, and (∂c2/∂p2)T differed from literature values by up to 7 ppm, 10%, and 5%, respectively. However, combining the results from the (3,0,0) or (4,0,0) modes of shorter resonator with the results from the (6,0,0) or (8,0,0) modes of the longer resonator yielded incorrect values of kB that varied from run-to-run. We speculate that these puzzling results originated in an unmodeled coupling, either between the two cavities (that resonated at nearly identical resonance frequencies in the same pressure vessel) or between the cavities and modes of the pressure vessel.

Electromagnetic resonances and their tunability in planar metamolecules isomer

Metamolecules consisting of multiple metallic microstructure show many novel electromagnetic phenomena due to the interaction between the resonators, which have important applications in the fields such as biosensor with high resolution and spaser. In this paper, we propose a trimeric planar metamolecules isomer array composed of three identical split ring resonators (SRRs) in each unit cell. Based on the finite difference time domain (FDTD) method, the numerical simulation demonstrates the resonant frequency, line-shape, and the coupling strength could be adjusted by tuning the orientation of resonator in each cell. Specifically, the coupled plasmonic resonance states could be tuned by the polarization of incident wave. The results provide a novel way to design metamaterials with multiple tunable resonant plasmonic states, which may be helpful to the related nano-photonic devices and the integration of optical-electronic.

Frequency comb generation by symmetry-protected bound state in the continuum

We study the dynamical response of two nonlinear microresonators coupled with a photonic crystal waveguide. We find a domain in the space of frequency and amplitude of the probing light where all stationary solutions are unstable. In this domain, scattered light carries multiple harmonics with equidistantly spaced frequencies [frequency comb (FC) effect]. Two identical resonators coupled with the waveguide support the symmetry-protected bound state in the continuum whose response is singular, as the amplitude of the injected wave tends to zero. As a result, the FC interval tends to zero when the amplitude of probing light diminishes, which paves the way for all-optical generation of waves with ultralow frequency.

Surface plasmon resonance sensor based on bimetallic alloys grating

A surface plasmon resonance sensor based on triangular alloys grating with high performance is proposed. The grating consists of homogeneous binary gold alloys of formula Au x M1−x , where M is silver, platinum and palladium. It is observed that the two metals, platinum and palladium, have an almost identical surface plasmon resonance in gold alloys irrespective of composition x. The resonance sensitivity becomes highly dependent on gold composition. The composition of gold around 0.1 is found to have a higher sensitivity. 0.1 composition of Au and 0.9 of Ag gives a high sensitivity. Consequently, the quality of the sensor is improved. Numerical simulations show that the angular sensitivity of the sensor reaches 100°/RIU and the full width at half maximum of the resonant dip is only 1.2°. Moreover, the sensor has not only a high sensitivity and a high resolution, but also a good linearity.