We demonstrate multiple Fano resonances in an integrated single dark mode hybrid metamaterial waveguide (HMW) structure, which consists of three gold cut wires placed on dielectric board waveguide. With a symmetrical pattern, the design shows double sharp Fano peaks with high Q-factors of 950 and 216, which are attributed to the interaction between plasmon mode and quasi-guided modes. By breaking the structural symmetry, a quadrupole mode on middle vertical cut wire is excited and further results in multiple Fano resonances through both the diffracted waves and near field coupling with bright-dark mode. Based on above properties, we show a high Q-factor refractive index (RI) sensor with the figure of merit (FOM) values of 330 and 281. Interestingly, these Q-factors of Fano peaks can be increased to 1357 and 361 to improve the sensing performance, by capping silicon layer on the metalsurface. This work provides a way to obtain multiple high Q-factor Fano resonances, which can widen channels for fabricating device in biochemical sensing.

Auroral kilometric radiations (AKR) are widely existing superluminous waves in the magnetosphere. Due to rarely available measurements of AKR magnetic field components, we derive the explicit expression of diffusion coefficients in terms of electric field components, which can be applied to various space plasma waves. Using Van Allen Probes data, we calculate diffusion coefficients with different harmonic orders for two AKR events. It is found that the first (higher) harmonic order contributes to diffusion coefficients at small (larger) pitch angles. The effect of higher harmonic orders becomes more significant as the electron energy increases. These results are contrary to the case of chorus wave, in which the first order usually contributes much to wave‐particle interactions. Estimations show that the phase space density of 0.5 MeV electrons can increase ∼10 times within 6 hr by AKR. This study is important for better modeling of AKR‐induced radiation belt electron dynamics.

We introduce a remarkably simple coplanar nanostructure consisting of two longer and one shorter graphene nanorods to support a Fano resonance, which arises from the coupling between bright mode and dark mode by breaking the geometrical symmetry. Simulation results, performed with the finite-difference time-domain method, show that the resonant frequency of the bright mode in the transmission spectrum can be independently tuned by changing the lateral offset of the shorter graphene nanorod, while changing its longitudinal offset can independently adjust the resonant frequency of the dark mode. Furthermore, Fano resonance spectrum can also be regulated actively by altering the Fermi energy of graphene as well as refractive index of the surrounding media. This letter proposes a unique modulation strategy of Fano resonance in metamaterials, assisting in developing potential in applications of sensor devices and some other plasmonic functional devices.

Although great achievements have been obtained in metasurfaces so far, the functionalities of these devices are almost static. The dynamically adjustable devices are far less explored. Here we theoretically and numerically demonstrate a veritable reconfigurable terahertz wavefront modulator (TWM). The designed TWM can dynamically shape the wavefront at will via imposing different Fermi levels on the constituent graphene ribbons. By adopting the Dirac brackets and Matrix analyze method, the correlation between the phase shift and Fermi level is theoretically established, which offers a general scheme for designing dynamically switchable devices. As a proof of concept, three different sets of pre-calculated Fermi levels are imposed on the graphene ribbons. The TWM can be dynamically switched among back reflector, varifocal metalens and Airy beam generator, which has never been demonstrated before as far as we know. The proposed reconfigurable TWM owns the capability of dynamically steering terahertz wavefront, indicating great significance for the development of THz reconfigurable devices.

The solar wind plays important roles on terrestrial magnetosphere dynamics, including the particle population and plasma waves generation. Here we report an interesting event that ULF waves are enhanced right after solar wind compression and the compressional mode ULF wave subsequently modulates both the intensity and energy flux direction of whistler-mode waves. Quasi-periodic whistler-mode wave packets are observed around L=5.6 at noon sector by Van Allen Probes. Growth rate calculation demonstrates that the compressional mode ULF wave can modulate the whistler-mode wave intensity by modulating the energetic electron anisotropy. Moreover, the direction of wave energy flux is observed to alternate between northward and southward at equator, which is probably because the intense ULF waves periodically alter the relative direction of the wave source region respect to the spacecraft. The current results provide a chain of observational evidences to illustrate how the generation and propagation of whistler-mode waves in the inner magnetosphere are affected by ULF waves during the solar wind dynamic pressure enhancement.

Magnetosonic (MS) waves are generally considered as electromagnetic harmonic fluctuations below the lower hybrid frequency. Here we present a correlated observation of proton ring‐like distribution and low harmonic magnetosonic waves with undetectable magnetic components (called QEMS). We conduct fully thermal simulations (WHAMP) to investigate the wave properties. The calculated growth rates can reproduce the observed spectral characteristics and demonstrate that the QEMS waves are excited as ion Bernstein modes by proton ring‐like distribution. The ratios between the wave electric and magnetic amplitudes E/B given by WHAMP indicate that the magnetic spectral densities are below the instrument noise level, and the ratios are ∼7–80 times larger than the wave phase speeds V_ph, suggesting that the QEMS waves are essentially quasi‐electrostatic, not just visually quasi‐electrostatic due to the measurement limit. This study provides further insights into the QEMS natures.