Near-field enhancement of a rod-like nanoantenna: Elctrostatic versus fully retarded results

The near-field enhancement of rod-like nanoantenna is studied in two variants: in the electrostatic approximation and in a fully retarded approach. A boundary integral equation (BIE) method has been used in the electrostatic approximation. The BIE method allows a transparent eigenmode decomposition of both the far-field and near-field, which are valid as long as the size of the nanoantenna is much smaller than every representative light wavelength. Our near-field calculations show that for a rod-like nanoantenna with a length below 100 nm the electrostatic and the fully retarded results are in good agreement with each other.