Ultimate Limit of Light Extinction by Nanophotonic Structures.

Nanophotonic structures make it possible to precisely engineer the optical response at deep subwavelength scales. However, a fundamental understanding of the general performance limits remains a challenge. Here we use extensive electrodynamics simulations to demonstrate that the so-called f-sum rule sets a strict upper bound to the light extinction by nanostructures regardless their internal interactions and retardation effects. In particular, we show that the f-sum rule applies to arbitrarily complex plasmonic metal structures that exhibit an extraordinary spectral sensitivity to size, shape, near-field coupling effects, and incident polarization. The results may be used for benchmarking light scattering and absorption efficiencies, thus imposing fundamental limits on solar light harvesting, biomedical photonics, and optical communications.