Highly efficient unidirectional forward scattering induced by resonant interference in a metal-dielectric heterodimer

Annular and unidirectional transverse scattering with high directivity based on magnetoelectric coupling

Transverse scattering is a special directional scattering perpendicular to the propagation direction, which has attracted great interest due to its potential applications from directional antennas, optical metrology to optical sensing. Here we reveal annular transverse scattering and unidirectional transverse scattering by magnetoelectric coupling of Omega particle. The annular transverse scattering can be achieved by the longitudinal dipole mode of the Omega particle. Furthermore, we demonstrate the highly asymmetric unidirectional transverse scattering by adjusting the transverse electric dipole (ED) and longitudinal magnetic dipole (MD) modes. Meanwhile, the forward scattering and backward scattering are suppressed by the interference of transverse ED and longitudinal MD modes. In particular, the lateral force exerted on the particle is accompanied by the transverse scattering. Our results provide a useful toolset for manipulating light scattered by the particle and broaden the application range of the particle with magnetoelectric coupling.

Study on the Controllable Preparation of Nd3+ Doped in Fe3O4 Nanoparticles for Magnetic Protective Fabrics

Magnetic protective fabrics with fine wearability and great protective properties are highly desirable for aerospace, national defense, and wearable protective applications. The study of the controllable preparation method of Nd3+ doped in Fe3O4 nanoparticles with supposed magnetic properties remains a challenge. The characterization of the microstructure, elemental composition, and magnetic properties of NdFe2O4 nanoparticles was verified. Then, the surface of NdFe2O4 was treated with glyceric acid to provide sufficient –OH. Subsequently, the connection of the nanoparticle by the succinimide group was studied and then grafted onto cotton fabrics as its bridging effect. The optimal loading rate of the functional fabrics with nanoparticles of an average size of 230 nm was 1.37% after a 25% alkali pretreatment. The color fatness to rubbing results showed better stability after washing and drying. The corresponding hysteresis loop indicated that the functional fabrics exhibited typical magnetism behavior with a closed “S” shape and a magnetic saturation value of 17.61 emu.g−1 with a particle size of 230 nm. However, the magnetic saturation value of the cotton fabric of 90 nm was just 4.89 emu.g−1, exhibiting controllable preparation for the aimed electromagnetic properties and great potential in radiation protective fields. The electrochemical properties of the functional fabrics exhibited extremely weak electrical conductivity caused by the movement of the magnetic dipole derived from the NdFe2O4 nanoparticles.

Dual-Wavelength Forward-Enhanced Directional Scattering and Second Harmonic Enhancement in Open-Hole Silicon Nanoblock

Nanostructures with appropriate sizes can limit light-matter interaction and support electromagnetic multipole resonance. The interaction between light and nanostructures is intimately related to manipulating the direction of scattered light in the far field as well as the electromagnetic field in the near field. In this paper, we demonstrate dual-wavelength directional forward-scattering enhancement in an individual open-hole silicon nanoblock (OH-SiNB) and simultaneously achieve bulk and surface electromagnetic field localization. The second harmonic generation is enhanced using electromagnetic field localization on the square hole surface. Numerical simulations reveal that the resonance modes, at λ₁ = 800 nm and λ₂ = 1190 nm, approximately satisfy the Kerker condition. In the near field, the magnetic dipole modes at dual wavelength all satisfy the boundary condition that the normal component of the electric displacement is continuous on the square holes surface, thus obtaining the surface electromagnetic field localization. Moreover, highly efficient second harmonic generation can be achieved at dual wavelengths using the surface electromagnetic field localization and the increased surface area of the square holes. Our results provide a new strategy for the integration of nanoantennas and nonlinear optoelectronic devices in optical chips.

Strong Field Enhancement and Unidirectional Scattering Based on Asymmetric Nanoantenna

Dielectric-metal nanostructures have lately emerged as one of the most promising approaches to modulating light at the optical frequency. Their remarkable electric and magnetic resonances give them a one-of-a-kind ability to augment local field enhancements with negligible absorption losses. Here, we propose a hybrid metal-dielectric-metal (MDM) nanoantenna that contains a dimer of three-layers of shell nanoparticles. In addition, we only theoretically and numerically show the optical properties of the hybrid dimer nanoantenna. We found that the nanoantenna sustained unidirectional forward scattering with narrow beamwidth (30.9 deg) and strong scattering intensity (up to 5 times larger than the single MDM particle). Furthermore, when the hybrid asymmetric dimer was excited by the plane wave with different electric polarization directions, our findings revealed that the hybrid nanoantenna boosted the gap’s electric near-field while also supporting unidirectional forward scattering. Finally, we analyzed the hybrid dimer with substrates of different materials. It supported strong electric high-order moments along the z-axis and x-axis in gaps between MDM nanoparticles and between MDM nanoparticles and the Ge substrate, owing to the intense displacement currents inside of the dielectric layer. We found that the local electric field of this MDM hybrid dimer nanoantenna with Ge substrate was well improved and attained 3325 v/m.

Complete Terahertz Polarization Control with Broadened Bandwidth via Dielectric Metasurfaces

We demonstrate terahertz dielectric metasurfaces with anisotropic multipoles within the framework of the generalized Huygens principle, in which the interference among these multipoles achieves giant phase shift with broadened bandwidth and high transmission coefficients. More importantly, owing to the anisotropic design, various phase delays between π/2 and 3π/2 are obtained, which convert the incident linearly polarized terahertz wave into right/left-handed circularly polarized light, elliptically polarized light and cross-polarized light. Both simulation and experimental results verify complete terahertz polarization control with the ellipticity ranging from 1 to - 1, which paves a way for polarization-related applications of terahertz meta-devices.

Multipolar scattering analysis of hybrid metal-dielectric nanostructures

We perform a systematic study showing the evolution of the multipoles along with the spectra for a hybrid metal-dielectric nanoantenna, a Si cylinder and an Ag disk stacked one on top of another, as its dimensions are varied one by one. We broaden our analysis to demonstrate the "magnetic light" at energies above 1 eV by varying the height of the Ag on the Si cylinder and below 1 eV by introducing insulating spacing between them. We also explore the appearance of the anapole state along with some exceptionally narrow spectral features by varying the radius of the Ag disk.