Dark modes in symmetric bulk Dirac semimetal dimers excited by cylindrical vector beams

Dark plasmonic modes with sharp spectral resonance peak and exceptionally high quality factor makes it essential for applications in bio-chemical sensing and fluorescence enhancement. Here, we investigate the mid-infrared spectral responses of bulk Dirac semimetal (BDS) dimers under focused azimuthally polarized and radially polarized cylindrical vector beams (CVB). Through numerical simulations, we obtained direct excitation of dark modes and revealed how the beams manipulate the dipole hybridization to produce these modes. By tuning Fermi energy of BDS, the resonant wavelength of the dark modes can be further adjusted. Our results may find the application of CVB in plasmonic sensing.

Improving the Sensitivity of Chipless RFID Sensors: The Case of a Low-Humidity Sensor

This study is supposed to introduce a valid strategy for increasing the sensitivity of chipless radio frequency identification (RFID) encoders. The idea is to properly select the dielectric substrate in order to enhance the contribution of the sensitive layer and to maximize the frequency shift of the resonance peak. The specific case of a chipless sensor suitable for the detection of humidity in low-humidity regimes will be investigated both with numerical and experimental tests.

Bulk plasmon polariton in hyperbolic metamaterials excited by multilayer nanoparticles for surface-enhanced Raman scattering (SERS) sensing

The capability to support large wave vector bulk plasmon polariton (BPP) waves enables the application of hyperbolic metamaterials (HMMs) in sensing. However, there is a challenge arising from the excitation of BPP, and the highly confined polarization waves are unable to meet the requirements of practical application. In this study, an HMM/bilayer silver nanoparticles (Ag NPs) platform is proposed that allows the excitation and utilization of BPP for use as a surface-enhanced Raman scattering (SERS) substrate. According to the research results, the bilayer Ag NPs provide stronger plasmonic property and act as a light-matter coupler, so as to generate a large wave vector of scattered light and excite the BPP within the HMM. Besides, Ag NPs provide the nano antenna structure, and decouple the BPP into localized surface plasmon (LSP) that can be used directly to excite the electric fields. In addition, HMM produces a modulating effect on the plasmon resonance peak, which makes it possible to overlap the spectrum of resonance peak with excitation wavelengths, thus leading to a strong absorption peak at the incident laser wavelength region. Experimentally, the platform was applied to achieve SERS detection for adenosine molecules with a concentration of 10−6 M. It is believed that this plasmonic platform has a potential of application in surface-enhanced spectroscopy.

Nonlinear Characteristics of Three-parameter Fluid Viscous Damper with Considering of Principal Stiffness and Hydraulic Stiffness

The three-parameter fluid viscous damper is used to isolate micro-vibration produced by control torque gyro (CMG) in satellite. In this paper, the damper is simplified by a single tube fluid viscous damper and two springs connected to the damping piston. With consideration of the principal stiffness of the bellows and the contraction and expansion effect of the damping orifice, the approximate analytical nonlinear model of the damper is established and verified by the computation fluid mechanics (CFD) method. Based on this analytical model, the displacement response of the damper and correction coefficient of hydraulic resistance are analyzed, the nonlinear characteristics in the frequency domain are also revealed. Furthermore, the energy consumptions of the nonlinear model and linear model are researched. The results show that the damper has an obvious amplitude at the first resonance peak, but not obvious at the second resonance peak. The vibration amplitude of the damping piston is only um level in the high-frequency domain. The correction coefficient of the hydraulic resistance at the resonance peak is much higher than other frequencies, which causes a significant nonlinear behavior. In addition, the energy consumption of the nonlinear model is larger than that of the linear model at the resonance peak, and the larger the resonance peak, the more obvious the phenomenon is. This means that the nonlinear damping can be used to further improve the suppression of the resonance peak of the three-parameter fluid viscous damper.

Transport through several four-quantum-dot topological structures

In this paper, several four-quantum-dot topological structures are designed. The influence of the interdot coupling strength and intradot Coulomb interactions on the conductance is discussed. The location of the anti-resonance band can be manipulated by tuning the interdot coupling strength, which suggests a physical scheme of an effective quantum switch. The Fano anti-resonance peak may evolve into a resonance peak. For the particular value of the interdot coupling strength, two Fano anti-resonances collapse and bound states in the continuum are formed. Moreover, many-body effect makes the number of anti-resonance bands increase. This study provides a theoretical basis for the design of quantum computing devices.

Characterizing Ground-Motion Amplification by Extensive Flat-Lying Sediments: The Seismic Response of the Eastern U.S. Atlantic Coastal Plain Strata

ABSTRACT We examine the effects that Atlantic Coastal Plain (ACP) strata have on ground motions in the eastern and southeastern United States. The ACP strata consist of widespread, nearly flat-lying sediments, the upper portions of which are unconsolidated or semiconsolidated. The ACP sediments are deposited primarily on crystalline basement rocks, creating large velocity and density contrasts with the underlying rocks. At 211 sites on ACP strata to thicknesses of 4000 m, we compute spectral ratios relative to the average of four bedrock sites west or northwest of the strata. Sites consist of stations of Earthscope’s USArray Transportable Array (TA), and temporary deployments in the Southeast Suture of the Atlantic Margin Experiment (SESAME), Eastern North American Margin (ENAM) experiment, and the DCShake deployment in Washington, D.C. For the TA and SESAME stations, we use signals from 13 teleseisms and three regional earthquakes as input, combining the north and east components of motion after taking the Fourier transforms. We also include similarly processed site responses from the ENAM and DCShake arrays that were computed in earlier studies. Results show prominent, fundamental resonance peaks at frequencies determined by reverberations in the entire sediment column, and that often define the largest amplifications for each frequency. As frequencies increase, these resonance peaks migrate to thinner ACP strata and increase in amplitude. The peaks are well defined at frequencies below about 1 Hz, but become narrower and less defined regionally at higher frequencies. We develop simple equations to characterize amplification versus ACP thickness, which we approximate by cosine and Gaussian curves with amplifications of 1 on bedrock and rising to the resonance peak, and then decreasing to an average amplification at thicknesses greater than twice the resonance peak. Comparisons with other site corrections for the central and eastern United States based on sediment thickness show similarities on thin ACP strata but divergence on thicker sediments. The results also demonstrate the effectiveness of using teleseismic arrivals to characterize the site responses of sedimentary sequences.

A simulation study of excitation contour of a linear trap with spatial harmonics

The process of nonlinear resonant excitation of ion oscillations in a linear trap is studied. There is still no detailed simulation of the resonance peak in the literature. We propose to use the excitation contour to describe the collective ion resonance. The excitation contour is a resonant mass peak obtained by the trajectory method with the Gaussian distribution of the initial coordinates and velocities. The following factors are considered: excitation time, low order hexapole and octopole harmonics with amplitudes A3 and A4, the depth of the initial ion cloud position. These multipoles are used for selective ion ejection from linear ion trap. All these factors affect the ion yield and the shape of the contours. Obtained data can be useful for control of such processes as ion fragmentation, ion isolation, ion activation, and ion ejection. Simulated resonance peaks are important for the theoretical description of the ion collective nonlinear resonances.

Simultaneous Measurements of Refractive Index and Methane Concentration through Electromagnetic Fano Resonance Coupling in All-Dielectric Metasurface

Dual-parameter measurements of refractive index and methane concentration based on electromagnetic Fano resonance are proposed. Two independent Fano resonances can be produced through electric dipole and toroidal dipole resonance in an all-dielectric metasurface separately. The linear relationship between the spectral peak-shifts and the parameters to be measured will be obtained directly. The refractive index (RI) sensitivity and gas sensitivity are 1305.6 nm/refractive index unit (RIU), −0.295 nm/% for one resonance peak (dip1), and 456.6 nm/RIU, −0.61 nm/% for another resonance peak (dip2). Such a metasurface has simpler structure and higher sensitivity, which is beneficial for environmental gas monitoring or multi-parameter measurements.