Multiple Resonant Modes Research Articles

Large-area long-wave infrared broadband all-dielectric metasurface absorber based on markless laser direct writing lithography.

Scalable and low-cost manufacturing of broadband absorbers for use in the long-wave infrared region are of enormous importance in various applications, such as infrared thermal imaging, radiative cooling, thermal photovoltaics and infrared sensor. In recent years, a plethora of broadband absorption metasurfaces made of metal nano-resonators with plasmon resonance have been synthesized. Still, their disadvantages in terms of complex structure, production equipment, and fabrication throughput, limit their future commercial applications. Here, we propose and experimentally demonstrate a broadband large-area all-dielectric metasurface absorber comprised of silicon (Si) arrys of square resonators and a silicon nitride (Si3N4) film in the long-wave infrared region. The multiple Mie resonance modes generated in a single-size Si resonator are utilized to enhance the absorption of the Si3N4 film to achieve broadband absorption. At the same time, the transversal optical (TO) phonon resonance of Si3N4 and the Si resonator's magnetic dipole resonance are coupled to achieve a resonator size-insensitive absorption peak. The metasurface absorber prepared by using maskless laser direct writing technology displays an average absorption of 90.36% and a peak absorption of 97.55% in the infrared region of 8 to 14 µm, and still maintains an average absorption of 88.27% at a inciedent angle of 40°. The experimentally prepared 2 cm × 3 cm patterned metasurface absorber by markless laser direct writing lithography (MLDWL) exhibits spatially selective absorption and the thermal imaging of the sample shows that the maximum temperature difference of 17.3 °C can exist at the boundary.

An ultra-thin ventilated metasurface with extreme asymmetric absorption

Recent progress in minimizing sound absorbers is driven by their great scientific significance and engineering value; however, compact devices for low-frequency sound are still challenging. Here, we construct an ultra-thin metasurface by parallel connecting resonators with high dissipation loss to a non-resonant reactance-dominated boundary (RDB) with high radiation loss, which realizes extreme absorption asymmetry at the exceptional point of scattering eigenvalue. We develop a parallel transfer matrix method to design the system, and a deep-subwavelength absorber (the operating wavelength is 120 times of its thickness) with 99.2% and 0.5% absorption for sound incident from opposite ports is achieved. The extreme absorption asymmetry is ascribed to the distinct coupling between the RDB and resonant meta-atom in an unbalanced dissipating state with excellent robustness against geometrical reconfigurations originated from the broadband near-unity reflection characteristics of the RDB. In particular, the proposed strategy brings the design of a degree of freedom rather than typical multiple resonant modes, and an extensible prototype showing >90% (<1%) absorptance for left- (right-) incidence within a wavelength from 23.3 to 18 times its thickness is demonstrated.

Broadband circularly polarized monopole antenna with modified characteristics

AbstractIn this letter, a novel wideband circularly polarized (CP) monopole antenna (CPMA) with modified characteristics is proposed. The CPMA comprises a rectangular ground with an L‐shaped strip, an inverted L‐shaped monopole, and an asymmetric U‐shaped strip as a parasitic element. Note that the proposed CPMA is fed by a coaxial probe instead of the traditional microstrip feed. The L‐shaped strip in the rectangular‐ground and parasitic asymmetric U‐shaped strip are used simultaneously to excite multiple CP resonant modes, which increase the CPMA's CP bandwidth. Both the simulated and measured results validate the proposed design. The proposed CPMA features a −10‐dB impedance bandwidth ranging from 2.06 to 4.05 GHz (65.1% centered at 3.055 GHz), and a wide 3‐dB axial ratio bandwidth ranging from 1.78 to 4.44 GHz (85.5% centered at 3.11 GHz), which has a potential application in the satellite digital audio radio service system.

Programmable particles patterning by multifrequency excitation radiation force of acoustic resonance modes

Acoustic radiation force has been extensively investigated to trap and spatially manipulate particles into various patterns. Existing acoustical methods for particles manipulation are developed by designing the acoustic structures or modulating the transducers arrays. These patterns and trajectories manipulation of particles have been limited to nodal lines by the prefabricated acoustic structures. Additionally, the acoustic potential field is limited by the wavelength due to the excitation of narrow frequency band, which is only suitable for local trapping and translation of particles. It is challenging to accomplish various programmable particles patterning by acoustic radiation force. In this work, we theoretically and numerically investigate the mechanisms for multifrequency excitation radiation force of acoustic resonance modes. The acoustic potential field can be programmed to arbitrary functional distributions by simultaneously exciting multiple resonance modes. Thus, we propose the programmable algorithm for arbitrary acoustic radiation potential, particles are trapped at the minima, forming a wide variety of patterns. Further, the selective manipulation of particles is realized by the programmable localized maximum of the acoustic radiation potential. Finally, the temporally modulated patterns of particles are achieved through modulating the positions of the localized maximum of acoustic radiation potential. This work paves the way for manipulation of arbitrary functional acoustic potential field, thereby opening up the realm of programmable particles patterning.

Design of InAs nanosheet arrays with ultrawide polarization-independent high absorption for infrared photodetection

InAs nanowires have been considered as good candidates for infrared photodetection. However, one-dimensional geometry of a nanowire makes it unsuitable for broadband light absorption. In this work, we propose and design InAs nanosheet arrays to achieve polarization-independent, angle-insensitive, and ultrawide infrared absorption. Simulations demonstrate that two-dimensional InAs nanosheets can support multiple resonance modes, thus leading to a strong and broadband absorption from visible light to mid-wave infrared. Moreover, we can tune polarization-dependent property in InAs nanosheets to be polarization-insensitive by forming a nanosheet based clover-like and snowflake-like nanostructures. We further optimized the design of InAs nanosheet arrays based on such structures and achieved high absorption (up to 99.6%) covering a broad wavelength range from 500 to 3200 nm. These absorption properties are much superior to their nanowire and planar film counterparts, making it attractive for infrared photodetection applications. The architecture of such nanostructures can provide a promising route for the development of high-performance room-temperature broadband infrared photodetectors.

Metal–Semiconductor–Metal Metasurface for Multiband Infrared Stealth Technology Using Camouflage Color Pattern in Visible Range

AbstractOptical stealth technology is being developed to cope with high‐sensitivity infrared image detectors and various guided detectors. Infrared stealth technology has remarkable performance; however, future advancements in multi‐band stealth technology covering the entire optical frequency range, from visible to wide infrared, are key challenges regarding unmanned surveillance systems. Thus, a metal–semiconductor–metal (MSM) metasurface with Fabry–Pérot (F–P) and multiple plasmonic resonant modes is introduced to realize multiband stealth technology. Different colors are obtained for printing camouflage patterns in the visible range using localized surface plasmon modes in Al disks on an opaque Ge layer. The F–P resonance of the Ge layer induces a strong absorption of >92% at 1.06 µm, reducing the guidance signal of the infrared laser‐guided detector. With an additional plasmonic resonance in the MSM metasurface, infrared signature reductions of >34%, >94.4%, and >97.7% are obtained for short‐wave, mid‐wave, and long‐wave infrared bands, respectively.

Design of Ultra-Wideband (UWB) Bandpass Filters Based on Interdigital Edge Coupled Lines: A Review

Since several decades ago, parallel coupled lines have found an extensive range of applications in order to design microwave circuits such us filter, impedance transformers and couplers. It gives advantages in term of low cost, easier integration with other devices and controllable performances by changing coupling coefficient between lines. This paper presents a review of parallel two and three interdigital coupled lines bandpass filters for ultra-Wideband (UWB) communication systems during previous years to achieve a fraction passband from 3.1 GHz to 10.6 GHz and then a FBW that can reach 109%. Different structures such as multiple-mode resonator, Short Circuited Stubs, Open stub, Stepped-impedance resonators and Rectangular Ring have been reportedly used to ameliorate the performances of developed filters.

Precision Multi-Mode Dielectric Characterization of a Crystalline Perovskite Enables Determination of the Temperature-Dependent Phase Transitions.

Simple perovskite crystals undergo structural phase transitions on cooling to low temperatures, which significantly change the material properties of the crystal. In this work, we rigorously characterize the temperature evolution of permittivity of a perovskite crystal as it undergoes phase transitions. In particular, we have undertaken precision measurements of a single crystal of Strontium Titanate from 294.6 to 5.6 K, by measuring the frequency of multiple microwave transverse electric (TE) and magnetic resonant modes simultaneously. The multi-mode microwave measurement technique of resonant frequency used in this work allows high precision determination of any induced anisotropy of the permittivity as the crystal undergoes structural phase transitions. Compared with previous results, we unequivocally show that the permittivity has an isotropic value of 316.3±2.2 at room temperature, consistent with its well-known cubic structure, and determine the onset of dielectric anisotropy as the crystal is cooled to lower temperatures. We show that the crystal exhibits uniaxial anisotropy in the permittivity below 105 K when the structure becomes tetragonal, and exhibits biaxial anisotropy in the permittivity below 51 K when the structure becomes orthorhombic.

Acceleration Trajectory Using Polydyne Curve to Ramp Up and Down for Suppressing Residual Vibrations Related to Multiple Mechanical Resonant Modes

Acceleration Trajectory Using Polydyne Curve to Ramp Up and Down for Suppressing Residual Vibrations Related to Multiple Mechanical Resonant Modes

ULTRA-WIDEBAND DIELECTRIC RESONATOR ANTENNAS: UNDERSTANDING OF MODAL ANALYSIS AND ITS RECENT ADVANCES

This paper presents a brief review of the development of Dielectric Resonator Antennas (DRAs) targeting Ultra-wideband(UWB) bandwidth range by exciting higher resonant modes or a combination of multiple resonant modes. Different schemes that have been tried to excite various modes of the resonator are reported. The expressions for the resonant frequency, fundamental and higher mode configurations of different geometries are stated. The information assists in the selection of the different antenna geometries for the UWB frequency range by generating different order modes for modern communication systems

Ultra-broadband long-wave infrared metasurface absorber based on Peano fractal curve

Fractals have emerged as a promising platform for realizing broadband absorption metasurfaces. In this paper, we propose an ultra-broadband absorber with high absorption operational in the long-wave infrared regime by means of a second-order Peano fractal curve (PFC) metasurface with a four-layer insulator–metal–insulator–metal (Ge/Cr/Ge/Cr) waveguide structure. The unique space-filling shape of the PFC enables the generation of multiple gap plasmon resonance modes, which expands the bandwidth of the absorber. In addition, the hybridization of these modes with cavity mode resonances and localized surface plasmon resonances enhances the average absorption of the device in the spectrum of operation, with an average absorption of 94.3% obtained for TM-polarized light with wavelengths between 12.3 µm and 32 µm in our simulations. A second-order quasi-PFC is designed for polarization-insensitive broadband absorption. Our findings establish general and systematic strategies for guiding the design of metamaterial absorbers with excellent broadband absorption.

Material–structure integrated design for ultra-broadband all-dielectric metamaterial absorber

Material and structure are the essential elements of all-dielectric metamaterials. Structure design for specific dielectric materials has been studied while the contribution of material and synergistic effect of material and structure have been overlooked in the past years. Herein, we propose a material–structure integrated design (MSID) methodology for all-dielectric metamaterials, increasing the degree of freedom in the metamaterial design, to comprehensively optimize microwave absorption performance and further investigate the contribution of material and structure to absorption. A dielectric metamaterial absorber with an ultra-broadband absorption from 5.3 to 18.0 GHz is realized. Theoretical calculation and numerical simulation demonstrate that the symphony of material and structure excites multiple resonance modes encompassing quarter-wavelength interference cancellation, spoof surface plasmon polariton mode, dielectric resonance mode and grating mode, which is essential to afford the desirable absorption performance. This work highlights the superiority of coupling of material and structure and provides an effective design and optimization strategy for all-dielectric metamaterial absorbers.

Digital Multiplexing of Rectangular Gratings for Multiple Independent Resonance Modes

Multiplexed gratings can provide multiple independent resonance modes for control of light–matter interactions. Here, we propose a method to digitally multiplexing rectangular metal gratings that can be fabricated with planar processing technologies, and adaptable to various structure and material systems. As different logic operators (OR, AND, XOR) may be applied in the multiplexation, we investigate their influences on plasmonic resonance properties of as–multiplexed metallic gratings, as well as dependences of their performances on structure features of the constitutive gratings. It’s concluded that, generally, the OR–operation on constitutive rectangular metal gratings with a medium ratio of ridge–width to period generates optimal multiplexed gratings that have excellent plasmonic resonance figures and are less critical for fabrication. The proposed structures may be applied in developing sensors and optoelectronic devices for improved performances or novel functions.

Metal-free super-wideband THz absorber for electromagnetic shielding

A technique is implemented for obtaining the high absorption over super-wideband (SWB) in a metal-free THz absorber. The multiple resonant modes with wide spectra are generated in a graphite-based resonator placed on a dielectric cavity merging of which provides the SWB response. The low permittivity dielectric slab sandwiched between the graphite sheet at its bottom and graphite resonator at its top acts as the Fabry–Perot cavity where absorption takes place. The high absorption rate of graphite in the THz regime can make it a suitable candidate for its utilization in implementing the broadband absorber. Thus, the molecular transition due to interaction of energy in graphite also provides the high absorption. The absorption bandwidth can further be enhanced by stacking of multiple layers in two different configurations of the proposed unit cell. The absorber maintains the polarization insensitivity due to symmetry and allows the high absorption for the electromagnetic wave incident up to the angle of more than The proposed absorber can be utilized in the THz electromagnetic shielding applications due to its SWB response.

Performance Enhancement of Broadband Circularly Polarized Slot–Microstrip Antenna Using Parasitic Elements

In this letter, two novel broadband circularly polarized (CP) slot–microstrip antennas (SMPA) with circular and square structures are elaborated. The circular SMPA is composed of four crown patches as parasitic elements, four crown slots etched on a circular ground, and a circular loop sequential phase feeding structure (SPFS). However, the square SMPA consists of four parasitic rectangular patches, four square slots with cut corners, and a square-loop SPFS. In the circular SMPA, the parasitic crown patches and crown slots are used to excite multiple CP resonant modes, which are fed by a circular loop SPFS through capacitive coupling. Combined with these CP modes, the CP bandwidth of the presented antenna could be improved. Eventually, the proposed circular SMPA has a broad 3 dB axial ratio bandwidth of 20.6% (5.20–6.40, 5.8 GHz) and a wide −10 dB impedance bandwidth of 25.8% (4.92–6.38, 5.65 GHz), which could occupy the wireless local area network (5.725–5.85 GHz), ITS (5.8 GHz), and WIFI (5.85–5.925 GHz) bands.

Optimization Based on the Surface Plasmon Optical Properties of Adjustable Metal Nano-Microcavity System for Biosensing.

This paper mainly studies the plasma optical properties of the silver nanorod and gold film system with gap structure. During the experiment, the finite element analysis method and COMSOL Multiphysics are used for modeling and simulation. The study changes the thickness of the PE spacer layer between the silver nanorod and the gold film, the conditions of the incident light and the surrounding environment medium. Due to the anisotropic characteristics of silver nanorod, the microcavity system is extremely sensitive to the changes of internal and external conditions, and the system exhibits strong performance along the long axis of the nanorod. By analyzing the extinction spectrum of the nanoparticle and the electric field section diagrams at resonance peak, it is found that the plasma optical properties of the system greatly depend on the gap distance, and the surrounding electric field of the silver nanorod is confined in the gap. Both ends of the nanorod and the gap are distributed with high concentrations of hot spots, which reflects the strong hybridization of multiple resonance modes. Under certain excitation conditions, the plasma hybridization behavior will produce a multi-pole mode, and the surface electric field distribution of the nanorod reflects the spatial directionality. In addition, the system is also highly sensitive to the environmental media, which will cause significant changes in its optical properties. The plasma microcavity system with silver nanorod and gold film studied in this paper can be used to develop high-sensitivity biosensors, which has great value in the field of biomedical detection.

Dual-Band Antenna Integrated With Solar Cells for WLAN Applications

A single-port dual-band antenna integrated with solar cells is reported for the 2.4/5-GHz wireless local area network (WLAN) applications. Thirty solar cells are adopted and integrated into the antenna structure for both energy harvesting and wireless communication. The solar cells can act as a director for the lower band, and the main radiation structure for the higher band. The slot and microstrip antennas are incorporated into the compact structure and multiple resonant modes are utilized for dual-band performance. The measurement results show that the lower band is from 2.27 to 2.5 GHz with an omnidirectional radiation pattern and the upper band is from 4.8 to 6.9 GHz with a directional radiation pattern. The proposed solar cell antenna can provide a dual-band performance with the ability of DC power generation, which can be a potential candidate for future green low-carbon communication.

Wide stopband single layerquasi‐elliptic ultra‐widebandbandpass filter

This paper presents the design of a microstrip ultra-wideband (UWB) bandpass filter that exhibits desirable characteristics of low-loss, high selectivity, wide stopband and high out-of-band rejection at room temperature. These characteristics are normally achieved with high temperature superconductor filters that require cryogenic cooling. The design of the proposed filter was realized by exciting multiple resonant modes in a unique Z-shaped microstrip resonator. The admittance of the filter configuration can be tuned prior to fabrication to adjust its center frequency by about 11.5% without affecting the profile of the bandpass response however this can have an impact of the loss. The proposed configuration allows adjustment of the upper and lower transmission zeros defining the bandpass response by 20.5% and 11.4%, respectively, without degrading the overall filter response. The low-loss quasi-elliptic function UWB bandpass filter design was fabricated on a commercially available dielectric substrate using standard PCB technology and its performance verified. The fabricated filter exhibits insertion-loss of 0.68 dB and return-loss better than 17 dB.

An Estimation Method of an Electrical Equivalent Circuit Considering Acoustic Radiation Efficiency for a Multiple Resonant Transducer

The electrical equivalent model of an underwater acoustic transducer must be exactly defined in the operating frequency band to improve the driving efficiency between a sonar transmitter and a transducer. This paper used the PSO (particle swarm optimization) algorithm to estimate electrical equivalent circuit parameters of a transducer that has multiple resonant modes. The proposed method used a new fitness function to minimize the estimation error between the measured impedance of the transducer and the estimated impedance. The difference to the previous method is that the proposed method considered interference effects of the adjacent resonant modes. Additionally, this paper analyzed the effective power and separated the mechanical and acoustical resistance by considering the acoustic radiation efficiency of the transducer. As a result, the proposed method estimated all parameters at the resonance points which are influenced by the adjacent resonant modes.

Additively Manufactured Deformation-Recoverable and Broadband Sound-Absorbing Microlattice Inspired by the Concept of Traditional Perforated Panels.

Noise pollution is a highly detrimental daily health hazard. Sound absorbers, such as the traditionally used perforated panels, find widespread applications. Nonetheless, modern product designs call for material novelties with enhanced performance and multifunctionality. The advent of additive manufacturing has brought about the possibilities of functional materials design to be based on structures rather than chemistry. With this in mind, herein, the traditional concept of perforated panels is revisited and is incorporated with additive manufacturing for the development of a novel microlattice-based sound absorber with additional impact resistance multifunctionality. The structurally optimized microlattice presents excellent broadband absorption with an averaged experimental absorption coefficient of 0.77 across a broad frequency range from 1000 to 6300Hz. Extensive simulation and experiments reveal absorption mechanisms to be based on viscous flow, thermal and structural damping dissipations while broadband capabilities to be on multiple resonance modes working in tandem. High deformation recovery up to 30% strain is also possible from the strut-based design and viscoelasticity of the base material. Overall, the excellent properties of the microlattice overcome tradeoffs commonly found in conventional absorbers. Additionally, this work aims to present a new paradigm: revisiting old concepts for the developments of novel materials using contemporary methods.