Enhanced Forward Scattering of Ellipsoidal Dielectric Nanoparticles

Abstract

Dielectric nanoparticles can demonstrate a strong forward scattering at visible and near-infrared wavelengths due to the interaction of optically induced electric and magnetic dipolar resonances. For a spherical nanoparticle, the first Kerker’s condition within dipole approximation can be realized, where backward scattering can reach zero. However, for this type of dielectric sphere, maximum forward scattering without backward scattering cannot be realized by modulating the refractive index and particle size of this nanoparticle. In this paper, we have demonstrated that a larger directional forward scattering than the traditional spherical nanoparticle can be obtained by using the ellipsoidal nanoparticle, due to the overlapping electric and magnetic dipolar modes. For the oblate ellipsoid with a determined refractive index, there is an optimum shape for generating the suppressed backward scattering along with the enhanced forward scattering at the resonant wavelength, where the electric and magnetic dipolar modes overlap with each other. For the prolate ellipsoid, there also exist the overlapping electric and magnetic dipolar modes at the resonant wavelength of total scattering, which have much higher forward scattering than those for both oblate ellipsoid and sphere, due to the existence of the higher multipolar modes. Furthermore, we have also demonstrated the realization of the dimensional tailoring in order to make the strong forward scattering shift to the desired wavelength.

Directional scattering and multipolar contributions to optical forces on silicon nanoparticles in focused laser beams

“…Recent studies show that optimal forward-to-backward scattering is obtained for spheroidal shapes rather than spheres due to their better overlap between electric and magnetic dipole resonances [36,37]. Since the interference force in the radiation pressure (F (int) p ) stems from asymmetric scattering, we calculated the optical forces and optical potential depth for spheroidal silicon particles [ Fig.…”

“…Moreover, we use symmetry to separate the gradient forces from the radiation pressure and discuss the multipolar contributions to each component. Since optimal forward-to-backward scattering ratios are not found in spherical high-index particles but rather in ellipsoidal shapes [36,37], we finally investigate the optical trap stability for deformed silicon spheres.…”

Facile Preparation of VO2 Films with Enhanced Luminous Transmittance and Infrared Modulation Ability

“…However, the island-like particles of VO 2 turned into a metallic state with a lower refractive index after MIT. The resonance wavelength of VO 2 in the metallic state may be consistent with 800 nm and suppressed the backward scattering while increasing forward scattering, , yielding A4 with an abnormally increased luminous transmittance in the metallic state. Moreover, the average luminous transmittance of A4 at room temperature was only 5.4%.…”

Scattering asymmetry and second Kerker condition

“…where α l and β l are the so-called electric and magnetic scattering phase shifts, are identical, i.e. a l = b l ⇐⇒ α l = β l , the zero optical backscattering condition is fulfilled [10][11][12][13][14][15]. This physical phenomenon is associated to the maximization of the asymmetry parameter in the electromagnetic dipolar approximation [16].…”