On the limits of quasi-static theory in plasmonic nanostructures

Abstract The approximated analytical approach of quasi-static theory (QST) is widely used in modelling the optical response plasmonic nanoparticles. It well known that its accuracy remarkable provided particle much smaller than wavelength interacting radiation and field induced inside structure approximately uniform. Here, we investigate limits QST range validity for gold nanostructures freestanding air. First, compare predictions scattering spectra nanospheres cylindrical nanowires various sizes with exact results by Mie theory. We observe a non-monotonic behaviour error as function characteristic length nanostructures, revealing non-trivial scaling scatterer size. Second, study elliptical section upon different excitation conditions performing finite element numerical analysis. Comparing simulation estimates extinction cross-section, find strongly dependent on conditions, yielding good even if highly inhomogeneous structure.