Figure 2.

Interferences between electric multipoles. (a) In-plane scattering patterns of a single dipole (dashed curve) and two separated dipoles (solid curve). The two dipoles are of the same magnitude and they possess a π/2 phase difference. The distance between them is λ/4, where λ is the effective wavelength of the interfering fields. (b) The interferences of two EDs supported by metal discs can route light of different colours to different directions. (c) A flat metasurface consisting of perpendicular metal-bar pairs as unit cells can couple incident circularly polarized light into SPP waves propagating in opposite directions which are helicity-dependent. To enhance the coupling efficiency, the horizontal periodicity is designed to be the effective wavelength of the SPP waves (λ_SPP). (d) In-plane (red curve) and out-of-plane (blue curve) scattering patterns of the spherical particle with simultaneous dipole and quadrupole excitation (a₁=a₂). (f) Perfect backward scattering elimination and forward scattering enhancement obtained by a metal ring (e) through interferences of the electric dipole and quadrupole modes. The inset in (f) shows the full in-plane angular scattering pattern. Adapted from: (a) [20], (b) [21], (c) [22], (d) [23] and (e,f) [24].