New publication provide an alternative view about the Kerker's condition for directional scattering

Broadband active tuning of unidirectional scattering from nanoantenna using combined radially and azimuthally polarized beams . Traditional Kerker's condition deals with linearly plane wave illumination, where a single wavelength can fulfill this condition on direction forward/backward scattering, thus very narrow-band. Our proposed scheme is based on separate control over the induced electric dipole and induced magnetic dipole using two coherent focused beams of radial polarization and azimuthal polarization, respectively. By carefully tuning the amplitude and phase relation of the two beams, a broadband unidirectional scattering can be achieved, even at the antenna’s resonant wavelength where the antenna scatters efficiently. By moving the focus of one beam, a drastic switch of the unidirectional scattering can be observed. Such a scheme enables the design of ultra-compact optical switches and directional couplers based on nanoantennas. PS. More detailed discussion will be added when I have more time. Lei