Even-order Resonance Research Articles

Design and Tensor Impedance Analysis of 4×4 Isotropic Homogeneous Metasurface-Backed Slotted Dual-Layered Bio-Superstrate-Loaded MPA

A 4×4 Isotropic Homogeneous Metasurface (IHM) backed, rectangular slotted dual-layered triband microstrip patch antenna (MPA) is proposed in this article. A detailed mathematical way to analyze the tensor surface impedance matrix (TSIM) of the proposed 4×4 IHM and slotted patch is demonstrated. The proposed IHM-backed MPA has a triband even-mode resonance at fr0=2.45 GHz, 2fr0=5.4 GHz, and 4fr0=7.7 GHz. A better and more accurate estimation of bio-superstrate loading effect for triband resonance is employed using the human skin (εr=52.79, σs=1.39) and blood (εr=52.8, σs=1.23) layer on the top of dual-layered metasurface-backed slotted MPA. TSIM characterization is observed for both blood- and skin layer-loaded dual-layered metasurface-backed slotted MPA. Chicken breast (εr=55.2, σs=1.49, and tanδ=0.325) with blood (εr=58.2, σs=2.59, and tanδ=0.364) is loaded onto fabricated dual-layered structure to verify numerically modeled estimation. A closed form triband, even-order resonance mode (i.e., fr0, 2fr0, and 4fr0) estimation based on dielectric superstrate thickness (Hs) is numerically established using MATLAB solver. Complete measurement setup with simulated vs. measured results is compared in this article.

Resonance-order-dependent plasmon-induced transparency in orthogonally arranged nanocavities.

We investigate plasmon-induced transparency (PIT) in a resonator structure consisting of two orthogonally arranged metal-insulator-metal nanocavities. Finite-difference time- domain simulations reveal that when both cavities in this structure resonate at the same frequency, the PIT effect can be used to induce spectral modulation. This spectral modulation depends on the resonance order of the cavity coupled directly to the external field, as it occurs when first-order resonance is exhibited but not with second-order resonance. We confirmed that this behavior is caused by the discrepancies between odd-order and even-order resonances using classical mechanical models analogous to nanocavities. By tuning the resonance frequency and resonance order of the cavities, one can modulate the spectrum of the resonator structure in an order-selective manner. The resonant order-dependent PIT provides insight into the development of metamaterials that function only at specific resonant orders for incident waves of various bands.

Selective Emitter with Engineered Anisotropic Radiation to Minimize Dual-Band Thermal Signature for Infrared Stealth Technology.

Selective emitters comprising plasmonic resonators have been exploited for cooling devices or infrared stealth technology. While selective emitters have been designed using odd-order resonances, even-order resonances also emit anisotropic thermal radiation signals. Thermal radiation by even-order resonances in selective emitters can be experimentally detected by thermal imaging cameras, and such thermal emissions often degrade the observability of infrared detectors, rendering them inapplicable to infrared stealth technology. Here, a selective emitter with extremely low thermal radiation signature in a dual-band range, a detection range by an infrared detector, is proposed with engineering anisotropic thermal radiation by even-order resonances. To minimize infrared signature in a dual-band range, the characterization of even-order resonances of gap plasmon metasurfaces is achieved based on vectorial diffraction within a relative error of 10%. Thermal radiation by even-order resonance has been shown to be highly directional and can be experimentally measured using mid-wave infrared images. Based on model prediction, the proposed selective emitter reduces mid-wave infrared signatures and long-wave infrared signatures by factors of 37.95 and 38.06, respectively, compared with those of blackbody surfaces. In addition, numerically confirmed thermal signature reduction and captured mid-wave infrared images indicate excellent thermal camouflage performance of the selective emitter with background medium. Thus, the characterization of even-order resonances provides a basis for the design of metasurfaces that can be employed for multispectral applications, especially infrared stealth technology.

Insertion effects of natural dielectric between artificial dielectrics formed by metallic sub-wavelength slit arrays

We investigated the optical transmission properties of a metamaterial system in which a natural dielectric is inserted between metallic sub-wavelength slit arrays that behave as an artificial dielectric when the incident light wavelength is longer than the slit periodicity. Transmission spectra were measured using terahertz time-domain spectroscopy, and the experimental results were analyzed by simulations based on the finite-difference time-domain method. We revealed that the resonance characteristics are defined by the two diffraction-limit frequencies for the inner and outer openings of the slits, which are different for the insertion of the dielectric. We also determined further details on the blue-shift behavior specific to the even-order resonance modes by accounting for the refractive index of the inserted intermediate dielectric. In addition, we experimentally demonstrated that insertion of a dielectric having a high refraction index enhances the frequency repulsion at the anticrossing, i.e., the coupling strength, between the symmetric and antisymmetric optical modes. These experimental and theoretical results will be essential for understanding and developing applications for hybrid systems composed of dielectrics with both fixed and widely tunable refractive indices.

Nearly perfect resonant absorption of TE-polarized light at metal surfaces coated with arrayed dielectric stripes

A quasi-transverse electric (TE) surface wave mode exists at a metal surface coated with an ultrathin high-index dielectric layer. As the coating is in dielectric stripe arrays, nearly perfect absorption of TE-polarized incidence light is observed in simulations, due to resonances of the quasi-surface waves at each segment of the dielectric-coated metal surfaces. In analysis, the Fabry-Perot-like nature of the resonances is clarified, and effects of symmetry on different behaviors of the odd- and even-order resonance modes are discussed. While the absorption peak is tunable, perfect absorption appears near cut-off wavelength of the surface mode.

Stability of equilibrium solutions in the critical case of even-order resonance in periodic Hamiltonian systems with one degree of freedom

The stability in the Lyapunov sense of an equilibrium position in a periodic Hamiltonian system with one degree of freedom is studied. It is assumed that the equilibrium is stable in the first approximation and that there exists an even resonance of order $$k$$ , arbitrary. The critical case is considered, i.e., when the system of parameters is such that, in order to draw rigorous conclusions about the stability of the equilibrium position in the Lypaunov sense, terms or order higher than three in the series expansion of the Hamiltonian function must be taken into account. Sufficient conditions are derived for stability and instability.

High transmission of annular aperture arrays caused by symmetry breaking

The terahertz transmission properties of symmetrical and asymmetrical annular apertures arrays (AAAs) are investigated both experimentally and numerically. It is found that only odd-order resonant modes are observed for the symmetrical structures but both odd- and even-order resonances can be shown for the asymmetrical structures. Breaking the symmetry of AAAs by gradually displacing the H-shaped AAAs with U-shaped AAAs allows an intensity modulation depth of $98.7%$ of the second-order resonance. Simulation results verify the experimental conclusions well. This result provides a tremendous opportunity for terahertz-wavelength tunable filtering, sensing, and near-field imaging.

Wideband Microstrip Ring Resonator Bandpass Filters Under Multiple Resonances

A new class of wideband microstrip bandpass filters is proposed under multiple resonances of an asymmetric ring resonator. Two capacitive coupling elements are placed at two perpendicular positions of a squared ring, whereas a pair of open-circuited stubs is formed in the symmetrical plane of these two excited ports similar to a dual-mode ring filter in shape. By stretching the paired stubs close to one-eighth of a wavelength, the first two even-order resonances move down to be quasi-equally located at two sides of the first odd-order resonance, thus forming a triple-resonance ring resonator. As interdigital coupled lines are installed at two ports instead of lumped capacitors, two extra resonances can be moved into passband, thereby making up a quintuple-resonance ring resonator. To provide an insight into their operating mechanism, these ring resonators are characterized in terms of transmission line theory. Afterwards, various wideband microstrip ring resonator bandpass filters with one or two asymmetric ring resonators are optimally designed and fabricated. Simulated results are confirmed via experiment, showing good wideband filtering performance with widened/deepened upper stopband and sharpened rejection skirts outside the wide passband.

Broadband Transducers Using Effectively Graded Piezoelectric Plates for Generation of Short-Pulse Ultrasound

Broadband ultrasound transducers that utilize piezoelectric materials having an effectively graded piezoelectric parameter and/or an excitation electric field applied across the piezoelectric material are investigated. These transducers are constructed by forming a number of fine V-grooves on one surface of a piezoelectric plate. The broadband frequency characteristic of the proposed transducer is demonstrated by experiments of wave generation in water. Analysis by the finite-element method proves that even-order resonance modes are also excited in the plate with a grooved configuration.

The stability of neutral systems in the case of a multiple fourth-order resonance

The stability of the steady motions of multiparametric systems is investigated for the critical case of N pairs of purely imaginary roots when several internal fourth-order resonances interact with each other. The earlier investigations (see the survey /1/) covered only the interaction of odd-order resonances. In general, the problem of stability when there are even-order resonances is more complicated; even in the case of the simplest, single fourth-order resonance there is no algebraic criterion of stability /2/.

Normal form and stability of periodic systems with internal resonance: PMM vol. 40, n≗ 3, 1976, pp. 431–438

We examine the problem of the Liapunov stability of the zero solution of a multidimensional nonlinear differential equation system with periodic coefficients and holomorphic right-hand sides. We investigate the critical case when the characteristic equation of the linearized system has only complex-conjugate roots equal to unity in modulus and when definite integral relations (internal resonance) exist between the characteristic indices and the frequency of the unperturbed motion. For any type of resonance we give a normal form of the system by reducing the original problem to the problem of stability under internal resonance for autonomous systems, considered earlier in [1] ; this enables us to obtain necessary and sufficient conditions for the stability of a model system, i.e. For the most important cases of odd-order resonance. We show that in the majority of cases the instability of the model system implies the instability of the complete system. We show that an even-order resonance can lead to the asymptotic stability of the system. For a second-order system we give necessary and sufficient conditions for asymptotic stability with respect to the first nonlinear term in the normal form. We indicate the extension of the results obtained to the stability of Hamiltonian systems.