Simulated profiles of electric field intensity enhancement for differently shaped Au nanoparticles. Effective geometrical parameters of (a) semi-ellipsoid- and (b) parallelepiped-shaped Au nanoparticles on glass substrates correspond to sample R3 (see Table 1). Electric field profiles correspond to light wavelengths of 646 and 658 nm for semi-ellipsoid- and parallelepiped-shaped Au nanoparticles, respectively, which provide the maximal intensity enhancement. Electric field polarization and wave vectors lie in the profile plane under the normal incidence conditions. Dashed lines indicate nanoparticle and substrate borders. Different nanoparticle widths are shown due to the exploited model with identical nanoparticle base area for semi-ellipsoid- and parallelepiped-shaped Au nanoparticles (see ‘Methods’ section). Vertical dimension scale is increased for better visual perception.