A clear approach to nanophotonics: The resonant modes of plasmonic nanoparticle structures made of gold or silver endow them with an ability to manipulate light at the nanoscale. However, owing to the high light losses caused by metals at optical wavelengths, only a small fraction of plasmonics applications have been realized. Kuznetsov et al. review how high-index dielectric nanoparticles can offer a substitute for these metals, providing a highly flexible and low-loss route to the manipulation of light at the nanoscale. Science , this issue p. 10.1126/science.aag2472

We investigate the peculiarities of light scattering from subwavelength particles made of high-refractive-index materials caused by the coexistence of particular anapole modes of both electric and magnetic character. The similarities and differences of such anapole modes are discussed in detail. We also show that these two types of anapole modes can be supported simultaneously by subwavelength high-index spherical dielectric particles.

We reveal that an isotropic, homogeneous, subwavelength particle with high refractive index can produce ultra-small total scattering. This effect, which follows from the inhibition of the electric dipole radiation, can be identified as a Fano resonance in the scattering efficiency and is associated with the excitation of an anapole mode in the particle. This anapole mode is non-radiative and emerges from the destructive interference of electric and toroidal dipoles. The invisibility effect could be useful for the design of highly transparent optical materials. This article is part of the themed issue ‘New horizons for nanophotonics’.

We report a distinguished mechanism of using two interaction-free (uncoupled) cavities to realize an all-optical silicon diode with an extremely high contrast ratio. In contrast to existing examples of all-optical diodes, our unidirectional transmission results from mimicking Fano resonance in a compact and finite silicon waveguide. A Fano spectrum with an arbitrary asymmetric factor, resonant center, and linewidth is explicitly designed with two symmetric resonances, which can be separately realized and tuned in an insightful manner by two cascaded uncoupled cavities. The field localizations are inherently asymmetric. We show that if these double asymmetries (Fano spectrum and field localization) are integrated and controlled, an ultrahigh-contrast-ratio silicon Fano diode is accomplished. This finding provides a promising avenue for achieving an extremely compact optical switch and incorporating Fano resonance in silicon photonics.

3D supercritical resolved light-induced magnetic holography makes possible 1872 Tbit/in ³ ultrahigh-density data recording.