Because we limit our investigations to normal illumination (no depolarization) and due to the linearity of the fields, we assume that the polarization filter *after* the sample is equivalent to a polarized, normal incidence.

#### Normalization: {#normalization .unnumbered}

In the FW as well as in the BW scattering experiments, the intensity distribution of the respective lamp as well as the spectral response of the optical components was accounted for by the following normalization scheme: First, the background noise was substracted (DF measurement on the bare SOQ / glass substrate). Subsequently the data was normalized using the spectra of the respective lamps, measured through the bare substrate (“FW” setup) and via a white reference sample (“BW” setup). Since we measure FW and BW scattering on two entirely different setups, we cannot compare the spectra quantitatively. Therefore we use the scattering from the smallest cylindrical nanowire (“NW1”, $D\approx 50\,$nm, Fig. \[fig:fig3\]a bottom) for normalization of the data between the two measurement geometries: In sufficiently small NWs illuminated by TM polarized light, exclusively the fundamental dipolar TM$_{01}$ mode is excited. This results in an omni-directional scattering, corresponding to a dipolar source along the SiNW axis. Thus we can assume that the FW and 