Multiple Resonant Modes Research Articles

Magnetization enhanced the multiple magnetic domain-dominated resonance modes in stripe domain films

FeCoHf films with different Hf contents and thicknesses were deposited by composition-gradient sputtering. The results showed that the stripe domain (SD) structure emerges when the film thickness exceeds a critical thickness (220–330 nm), but the increase in introduced Hf leads to a decrease in magnetization, and in turn, the stripe phase weakens and eventually disappears. Dynamic measurements revealed magnetic domain-dependent resonant absorption spectra with up to seven resonance peaks, which have rarely been observed in magnetic film with an established SD structure. The number of resonant peaks can be controlled by the saturation magnetization of the film. Micromagnetic simulations indicate that multiple magnetic domain resonance modes can be attributed to the enhanced magnetization, which induces an increase in the magnetic domain wall volume. These results emphasize the pivotal role of magnetic domain dynamics in the framework of spintronic and microwave devices.

Multi-band optical resonance of all-dielectric metasurfaces toward high-performance ultraviolet sensing.

All-dielectric sensors featuring low-loss resonances have been proposed instead of plasmonic-based sensors. However, reported dielectric-based sensors generally work in the visible and near-infrared regions and detect the intensity variation of resonant modes because the electromagnetic energy is mainly confined inside dielectric nanoparticles. It is a challenge to adjust the hotspots from the inside to the surface of the all-dielectric metasurface. In this study, highly uniform Si3N4 all-dielectric metasurfaces have been successfully fabricated as sensing platforms by utilizing nanosphere self-assembly and plasma enhanced chemical vapor deposition techniques. Experimental and simulated results demonstrate that proposed Si3N4 all-dielectric metasurfaces exhibit multiple optical resonant modes in the ultraviolet and visible wavelength and present distinct field-confinement in the gaps of nanoparticles. The hotspots have been successfully adjusted to the surface of Si3N4 nanoparticles. Delightedly, Si3N4 all-dielectric metasurfaces show characteristic wavelength shifts with variation of the refractive index, and the sensitivity can reach 707 nm per RIU for trace detection as sensing substrates. Proposed Si3N4 all-dielectric metasurfaces are promising to act as high-sensitive sensing substrates in the ultraviolet and visible wavelength with the ease of high-throughput fabrication.

Antisymmetric localization of terahertz defect modes in a planar waveguide with undulated walls

Although various terahertz (THz) functional devices based on artificial materials have been widely proposed, their performance is still unsatisfactory due to the limitation of the involved guided wave modes. The introduction of defects can result in a strong localization effect, which has been found in applications of improving device performance. Due to Bragg resonances, the localization is usually symmetrical about the center of defects. Here, based on multiple mode resonances, we demonstrate an antisymmetric localization of THz waves in a periodic parallel plate waveguide with non-Bragg nature resonances. Unexpectedly, such resonances can produce two extremely narrow transmissions with a transmittance close to 1, and the narrowest linewidth can reach 2 MHz and the Q-factor is close to 7.44 × 105, which would be good candidates for THz filtering and sensing. Referring to the field distributions, we employ the mathematical operation symbols of the equal sign ‘=’ and the multiplication sign ‘×’ to intuitively mark these two antisymmetric localizations with different characteristics. The dispersion curves and mode analysis reveal that the observed antisymmetric localizations caused by non-Bragg resonances are induced by the first- and second-order transverse modes. Furthermore, the frequency of antisymmetric localizations can be manipulated by changing the geometry of defects. Our findings on extremely narrow transmission peaks and antisymmetric localizations pave a way for creating high performance THz functional devices, such as switches, filters, and sensors.

Multiparametric Guided-Mode Resonance Biosensor Monitoring Bulk and Surface-Film Variations

A guided-mode resonance (GMR) sensor with multiple resonant modes is used to measure the collection of biomolecules on the sensor surface and the index of refraction of the sensor environment (bulk). The number of sensor variables that can be monitored (biolayer index of refraction, biolayer thickness, and bulk, or background, index of refraction) is determined by the number of supported resonant modes that are sensitive to changes in these variable values. The sensor we use has a grating and homogeneous layer, both of which are made of silicon nitride (Si3N4), on a quartz substrate. In this work, we simulate the sensor reflection response as a biolayer grows on the sensor surface at thicknesses from 0 to 20 nm and biolayer indices of refraction from 1.334 to 1.43 RIU; simultaneously, we vary the bulk index of refraction from 1.334 to 1.43 RIU. In the specified span of sensor variable values, the resonance wavelength shifts for 2023 permutations of the biolayer index of refraction, biolayer thickness, and bulk index of refraction are calculated and accurately inverted. Inversion is the process of taking resonant wavelength shifts, for resonant modes of a sensor, as input, and finding a quantitative variation of sensor variables as output. Analysis of the spectral data is performed programmatically with MATLAB. Using experimentally measured resonant wavelength shifts, changes in the values of biolayer index of refraction, biolayer thickness, and bulk index of refraction are determined. In a model experiment, we deposit Concanavalin A (Con A) on our sensor and subsequently deposit yeast, which preferentially bonds to Con A. A unique contribution of our work is that biolayer index and biolayer thickness are simultaneously determined.

Compact multiband bandpass filters based on parallel coupled split structure multimode resonators

In this letter, a novel sext-band bandpass filter (BPF) using two split-type multiple-mode resonators is proposed. The filter is composed of two sets of resonators which are respectively designed to realize Filter 1 with two passbands and Filter 2 with quad passbands. Then the two BPFs are combined by parallel coupling feed lines for sext-band responses, and each of the six centre frequencies in the proposed sext-band BPF is able to be controlled due to the design freedom. To validate the design and analysis, a prototype filter has been fabricated with six passbands centred at 1.88/2.59/3.48/5.26/5.82/6.75 GHz. The measured result of the fabricated filter agrees well with the simulation, which shows that the proposed structure is a good candidate for sext-band BPF designs and validates the proposed design flow well.

Multi‐Level Bioinspired Microlattice with Broadband Sound‐Absorption Capabilities and Deformation‐Tolerant Compressive Response

AbstractOwing to the omnipresent noise and crash hazards, multifunctional sound‐absorbing, and deformation‐tolerant materials are highly sought‐after for practical engineering design. However, challenges lie with designing such a material. Herein, leveraging the inherent mechanical robustness of the biological cuttlebone, by introducing dissipative pores, a high‐strength microlattice is presented which is also sound‐absorbing. Its absorption bandwidth and deformation tolerance are further enhanced by introducing another level of bioinspiration, based on geometrical heterogeneities amongst the building cells. A high‐fidelity microstructure‐based model is developed to predict and optimize properties. Across a broad range of frequencies from 1000 to 6300 Hz, at a low thickness of 21 mm, the optimized microlattice displays a high experimentally measured average absorption coefficient of 0.735 with 68% of the points higher than 0.7. The absorption mechanism attributes to the resonating air frictional loss whilst its broadband characteristics attribute to the multiple resonance modes working in tandem. The heterogeneous architecture also enables the microlattice to deform with a deformation‐tolerant plateau behavior not observed in its uniform counterpart, which thereby leads to a 30% improvement in the specific energy absorption. Overall, this work presents an effective approach to the design of sound and energy‐absorbing materials by modifying state‐of‐the‐art bioinspired structures.

Elastic metamaterial with multiple resonant modes and asymmetric structure design for low-frequency vibration absorption

Elastic metamaterial with multiple resonant modes and asymmetric structure design for low-frequency vibration absorption

Multiple resonant modes coupling enabled strong CD response in a chiral metasurface.

The chiral structures with strong circular dichroism (CD) response and narrow linewidth are desirable in chiral sensing, circularly-polarized light detection, and polarization imaging. Here, we theoretically proposed a hybrid chiral metasurface for differential absorption of circularly polarized light. Based on the multiple resonant modes coupling effect in a two-dimensional dielectric slab, it is realizable then to achieve a nearly perfect absorption for right circularly polarized light and simultaneously reflects 90% of left circularly polarized light, suggesting the generation of strong CD of 0.886 within a narrowly spectral linewidth of 4.53 nm. The multipole analysis reveals that the electric dipole, the magnetic dipole, and the electric quadrupole make dominant contributions to chiral absorption and the high CD response in this metsurface. The excitation of guided mode resonance enhances the ability of this metasurface to absorb electric field. Moreover, the optical chirality response can be further manipulated through the geometry features. These findings pave a powerful way to realize the narrowing and strong CD platform for single-band and multiband chirality behaviors.

Research on Dual-Technology Fusion Biosensor Chip Based on RNA Virus Medical Detection.

In recent years, the emergence of COVID-19 and other epidemics caused by RNA(ribonucleic acid)-type genetic viruses has aroused the close attention of governments around the world on emergency response to public safety and health emergencies. In this paper, an electrodeless biosensing detection chip for RNA virus medical detection is designed using quartz crystal microbalance technology and local surface plasmon resonance technology. The plasmonic resonance characteristic in the nanostructures of gold nanorods-quartz substrates with different parameters and the surface potential distribution of the quartz crystal microbalance sensing chip were studied by COMSOL finite element simulation software. The results show that the arrangement structure and spacing of gold nanorod dimers greatly affect the local surface plasmon resonance of nanorods, which in turn affects the detection results of biomolecules. Moreover, high concentrations of “hot spots” are distributed between both ends and the gap of the gold nanorod dimer, which reflects the strong hybridization of the multiple resonance modes of the nanoparticles. In addition, by simulating and calculating the surface potential distribution of the electrode area and non-electrode area of the biosensor chip, it was found that the biosensor chip with these two areas can enhance the piezoelectric effect of the quartz chip. Under the same simulation conditions, the biochip with a completely electrodeless structure showed a better sensing performance. The sensor chip combining QCM and LSPR can reduce the influence of the metal electrode on the quartz wafer to improve the sensitivity and accuracy of detection. Considering the significant influence of the gold nanorod dimer plasma resonance mode and the significant advantages of the electrodeless biosensor chip, an electrodeless biosensor combining these two technologies is proposed for RNA virus detection and screening, which has potential applications in biomolecular measurement and other related fields.

Compact Quad-Mode BPF Based on Half-Mode Short-Circuited Semicircular Patch Resonator

Wideband bandpass filter (BPF) design using a half-mode patch resonator with multiple resonant modes is proposed in this paper. The resonator is formed from a short-circuited circular patch loaded with radial slots. The metallized vias are positioned in a circle. Its radius is used to tune the resonant frequencies of the resonator. According to the surface current distributions of the eigenmodes, different numbers of the radial slots can be distributed on the patch to prolong the current paths of the relevant eigenmodes, the resonant frequencies of which can be shifted down to that of the dominant mode, the TM010 mode. As a result, a semicircular patch resonator loaded with three slots is used to design a compact quad-mode wideband BPF, which employs TM010, TM110, TM210, and TM310 modes. Furthermore, the coupling between input and output feeding lines is introduced to realize two transmission zeros at both sides of the passband. Therefore, the selectivity is improved. The experiment has verified the theoretical analysis and the design approach.

Ultra-broadband and completely modulated absorption enhancement of monolayer graphene in a near-infrared region.

Achieving ultra-broadband and completely modulated absorption enhancement of monolayer graphene in near-infrared region is practically important to design graphene-based optoelectronic devices, however, which remains a challenge. In this work, by spectrally designing multiple magnetic plasmon resonance modes in metamaterials to be adjacent to each other, near-infrared light absorption in monolayer graphene is greatly improved to have an averaged absorption efficiency exceeding 50% in a very broad absorption bandwidth of about 800 nm. Moreover, by exerting an external bias voltage on graphene to change Fermi energy of graphene, the ultra-broadband absorption enhancement of monolayer graphene exhibits an excellent tunability, which has a nearly 100% modulation depth and an electrical switching property. This work is promising for applications in near-infrared photodetectors, amplitude modulators of electromagnetic waves, etc.

A multi-band terahertz plasmonic absorber based on fan-like metasurface

A plasmonic absorber composed of a sandwich structure based on a fan-like metasurface with three blades has been proposed. The multiple resonance modes are analyzed based on the finite-difference time-domain (FDTD) method by comparing electric field distributions between the unit of absorber with three blades and one individual blade, which proved that the three blades of metasurface can separately excite three absorption peaks in terahertz (THz) band. The influence of the geometry configurations on the resonance modes have also been studied, including radius of blades, the thickness of the top metal layer, and period of unit. The resonance frequencies can be easily tuned by changing the radius of metasurface unit. The proposed plasmonic absorber has potential for THz imaging and sensing applications.

A compact broadband microstrip slot circularly polarized antenna using parasitic elements

ABSTRACT A new broadband circularly polarized (CP) microstrip slot antenna (MSA) is proposed in this study. The proposed CP MSA is comprised of a square-loop feed configuration, four rectangular patches as parasitic patches, and a square ground plane etched with four L-shaped slots as parasitic slots. The square-loop feed configuration, which can stimulate a 270° phase difference, comprises an arc-shaped strip and a square-loop. Rectangular patches and L-shaped slots as parasitic elements are together arranged and etched at the side of the square-loop feed configuration to excite multiple CP resonant modes using a capacitively coupled feeding technology. A prototype of the proposed antenna was simulated, manufactured, and measured in this study. The measured results depict that the CP MSA features a wide impedance bandwidth of 4.36–5.36 GHz (20.6%) for|S11| < −10 dB and broad axial ratio bandwidth (ARBW) of 4.53–5.30 GHz (15.7%) for AR < 3 dB. Thus, the proposed CP MSA would be an outstanding candidate in wireless communication systems.

Anisotropic Acoustodynamics in Gigahertz Piezoelectric Ultrasonic Transducers

In this work, we employed our newly developed optical imaging method to probe detailed acoustodynamic physics in gigahertz unreleased ultrasonic transducers based on an AlN-on-silicon system, revealing mode superposition, anisotropic transduction, and dynamic mode evolution. Superpositioned upon the dominant breathing mode along the vertical direction of the AlN layer, multiple resonant lateral modes are identified, and they are shown to evolve into a surface mode beyond the piezoelectric transduction envelope, with strong anisotropic transduction brought by the shear motion of silicon. This acoustodynamic property is important for verifying and further improving design theories of broadband piezoelectric transducers and thin film piezoelectric-on-substrate systems in general.

Ultrabroadband Saline-Based Metamaterial Absorber With Near Theoretical Absorption Bandwidth Limit

Expanding the bandwidth for microwave absorption from L to Ka band with high efficiency remains challenging for broadband impedance matching. To overcome this challenge, an all-dielectric metasurface absorber composed of resin shell and saline structure is proposed to realize above 90% absorption from 0.9–40 GHz with a relative bandwidth of 191% (95.5% of theoretical limiting value) and thickness of 38 mm (115% of the minimum thickness). The extremely large bandwidth originates from coupled multiple resonance modes excited in dispersive saline structure, which can be larger with lower initial frequency by changing the geometry parameters based on the equivalent scale transformation method. Moreover, the polarization-independent and wide-angle broadband absorption are proved by both experimental and simulated results, offering practical potential application in ultrabroadband EM radiation prevention and stealth technology.

Simultaneous detection of multiple gases using multi-resonance photoacoustic spectroscopy

In this paper, a gas sensing technique based on multi-resonance photoacoustic spectroscopy (M-PAS) is firstly proposed for simultaneous detection of multi-component gas molecules. To explore the capabilities of this technique, a spherical resonator with multiple resonant modes and high quality factors are detailedly developed by theoretical simulation and experimental analysis. The proposed M-PAS technique combing with wavelength modulation spectroscopy (WMS) is investigated for simultaneous detection of H2O, CO2 and CH4, respectively. Based on Allan-Werle deviation analysis, the detection limits of 1.17 ppm for H2O, 83 ppm for CO2 and 1.76 ppm for CH4, respectively, at the integration time of 136 s, 181 s and 195 s were achieved, corresponding to the normalized noise equivalent absorption (NNEA) coefficient of 6.03 × 10−10 cm−1W/√Hz, 5.46 × 10−10 cm−1W/√Hz, 2.36 × 10−9 cm−1W/√Hz. The reported sensing technique has potential applications in atmospheric environment monitoring, industrial process control and breath gas analysis by appropriate improvements, and can easily be modified for other multi-component gas analysis.

Virtual Sensor Array Based on Piezoelectric Cantilever Resonator for Identification of Volatile Organic Compounds.

Piezoelectric cantilever resonator is one of the most promising platforms for real-time sensing of volatile organic compounds (VOCs). However, it has been a great challenge to eliminate the cross-sensitivity of various VOCs for these cantilever-based VOC sensors. Herein, a virtual sensor array (VSA) is proposed on the basis of a sensing layer of GO film deposited onto an AlN piezoelectric cantilever with five groups of top electrodes for identification of various VOCs. Different groups of top electrodes are applied to obtain high amplitudes of multiple resonance peaks for the cantilever, thus achieving low limits of detection (LODs) to VOCs. Frequency shifts of multiple resonant modes and changes of impedance values are taken as the responses of the proposed VSA to VOCs, and these multidimensional responses generate a unique fingerprint for each VOC. On the basis of machine learning algorithms, the proposed VSA can accurately identify different types of VOCs and mixtures with accuracies of 95.8 and 87.5%, respectively. Furthermore, the VSA has successfully been applied to identify the emissions from healthy plants and "plants with late blight" with an accuracy of 89%. The high levels of identifications show great potentials of the VSA for diagnosis of infectious plant diseases by detecting VOC biomarkers.

Tunable ultra-high quality factor graphene absorber based on semicylindrical silica array and distributed Bragg reflector structure

We propose a tunable narrowband absorber by utilizing a graphene monolayer placed between a dielectric semicylindrical array and a multilayer silica/silicon distributed Bragg reflector (DBR) structure. The multi-band perfect absorption can be achieved due to the excitation of multiple resonant modes in the absorber, including the guided mode resonance of the dielectric silica array and BR-based guided mode resonance in the DBR structure. The ultra-high quality factor (Q) is mainly attributed to the low external leakage loss of the resonator and the low intrinsic loss of the graphene monolayer. Moreover, the Q-factor of absorption peaks can be tuned by electrically controlling the Fermi energy of graphene. The sensitivity of a spectral wavelength shift for the refractive index change of the resonator is up to 730 nm/RIU, and the figure of merit is 1043. The proposed graphene-based metamaterial offers potential applications for photodetectors, optical modulators, and sensors in the near infrared frequency regime.

Compact Low-Cost Reconfigurable Microwave Bandpass Filter Using Stub-Loaded Multiple Mode Resonator for WiMAX, 5G and WLAN Applications

This paper presents a compact, low-cost reconfigurable bandpass filter (BPF) for WiMax, 5G, and WLAN applications. The BPF consists of a half-wavelength resonator folded as C-shaped by a pair of symmetrical PIN diodes and a central quarter-wavelength resonator to form an E-shaped stub-loaded multiple-mode resonator (SL-MMR). The feed line is made of two subsections separated by a gap which acts as a fixed capacitance and allows the filter to have bandpass behavior. The proposed filter is modeled using the even and odd mode analysis to predict the locations of the resonant frequencies. The simulation results show that the filter covers the frequency range (3.38-3.95) GHz with a center frequency of 3.52 GHz at the ON state of a pair of PIN diodes. On the other hand, the BPF covers the frequency range (4.7-5.93) GHz with a center frequency of 5.2 GHz, at the OFF state of the diodes. The results also show a small insertion loss at the filter passband with two sharp transmission zeros at the stopband.

New Circular-Slot Circularly Polarized Antenna with Modified Characteristic

In this article, a novel broad circularly polarized antenna (CPA) with circular-slot ground is presented. The circular-slot CPA is consisted of a circular-slot ground, an I-shaped slit and a semicircle loop feeding structure. By using semicircle loop feeding structure and adding a slit into the circular-slot ground as perturbation elements, the multiple CP resonant modes could be stimulated simultaneously. To demonstrate to the design radiational, an antenna model was printed, manufactured, and tested. The tested results reveal that the proposed antenna has a broad 3-dB ARBW of |S11| &lt; −10 dB that could be obtained, which is suitable for the application of wireless communication systems.