Computational Metamaterials: Optical signal processing of light waves can represent certain mathematical functions and perform computational tasks on signals or images in an analog fashion. However, the complex systems of lenses and filters required are bulky. Metamaterials can perform similar optical processing operations but with materials that need only be a wavelength thick. Silva et al. (p. 160 ; see the Perspective by Sihvola ) present a simulation study that shows how an architecture based on such metamaterials can be designed to perform a suite of mathematical functions to create ultrathin optical signal and data processors.

By applying the optical nanocircuit concepts to metasurfaces, we propose an effective route to locally control light transmission over a deeply subwavelength scale. This concept realizes the optical equivalent of a transmit-array, whose use is demonstrated for light bending and focusing with unprecedented efficiency over a subwavelength distance, with crucial benefits for nano-optics applications. These findings may lead to large improvements in the manipulation of optical transmission and processing of nanoscale optical signals over conformal and Si-compatible substrates.

Confinement of light is usually achieved by reducing the photonic density of states of the surrounding environment, as in waveguides and photonic crystal cavities. In contrast, optical bound states have been recently shown to exist within the radiation continuum in large periodic arrays, in analogy with embedded eigenvalues in certain quantum systems. Here we demonstrate that under special conditions it may be possible to induce three-dimensional photonic embedded eigenvalues in a subwavelength open scattering system. The striking properties of these optical states without radiation loss may lead to unprecedented light localization in nanophotonic structures.