FDTD simulations.

We measure the scattering from cylindrical SiNWs of diameters between $D\approx 50\,$nm and $D\approx 100\,$nm, epitaxially grown by the vapor-liquid-solid (VLS) technique and drop-coated on a transparent glass substrate. The NW size-dispersion was obtained via scanning electron microscopy (SEM) from a second sample consisting of the same SiNWs, drop-coated on a silicon substrate (see Fig. \[fig:fig2\]d). For details, see the methods section. Results of the scattering experiments are shown in Fig. \[fig:fig3\](a-c) for TE (top row) and TM (bottom row) polarized illumination. The given NW diameters are estimates, obtained by comparison with simulations.

The very weak (TE), respectively omnidirectional (TM) scattering in case of the the smallest nanowire (Fig. \[fig:fig3\]a, NW1: $D\approx 50\,$nm) is in perfect agreement with the GDM simulations and confirms the assumption of a purely dipolar response if only the non-degenerate TM$_{01}$ mode is excited (see also field plot for $\lambda=750\,$nm in figure \[fig:fig3\]d on the right). As expected, with increasing NW diameter (figure \[fig:fig3\]b-c), we observe a simultaneous red-shift of the FW and BW scattering peaks. For the largest SiNWs (Fig. \[fig:fig3\]c, $D\approx 100\,$nm), in the case of TE polarized illumination mainly FW scattering occurs in a limited spectral range ($550\,\text{nm} \lesssim \lambda \lesssim 