\end{aligned}$$ The simulated range is $0^{\circ} \leq \varphi_{\text{col., sim.}} \leq 90^{\circ}$. Given the excellent agreement between simulations and measurements, the deviations between the collection angles seem not to cause a serious problem. We attribute this to the fact that scattering is either omni-directional or else strongly forward/backward directional. In both cases, large angles with respect to the incident wave-vector direction contribute only weakly to the total scattering.

See also [SI, Fig. S16]{} for a detailed sketch, illustrating the collection angles.

GDM Simulations {#sec:methods_gdm}
---------------

Because of the high aspect ratio of the nanowires, we assume infinitely long structures (NW axis along $Y$). In this manner we simplify the computation to a two dimensional (2D) problem. The electric field is calculated using the Green dyadic method (GDM). Practically, we solve the vectorial Lippman Schwinger equation $$\label{eq:LippmannSchwinger}
\begin{aligned}
 \mathbf{E}^{\text{2D}}(\mathbf{r}_{\parallel},\omega,\mathbf{k}_y)\ =\
 \mathbf{E}_0^{\text{2D}}(\mathbf{r}_{\parallel},\omega,\mathbf{k}_y)\ + \\ 
 \int \mathbf{G}_0^{\text{2D}}(\mathbf{r}_{\parallel},\mathbf{r}_{\parallel}', \omega, \mathbf{k}_y) \cdot 
 \chi(\omega) \mathbf{E}^{\text{2D}}(\mathbf{r}_{\parallel}',\omega,\mathbf{k}_y) d\mathbf{r}_{\parallel}'
\end{aligned}$$ at the frequency $\omega$, by discretizing the nanostructure using square meshes. $\mathbf{E}_0^{\text{2D}}$ and $\mathbf{E}^{\text{2D}}$ are the incident field and resulting field inside the nanostructure, respectively. $\mathbf{G}_0^{\text{2D}}$ is the Green’s dyad and $\chi$ the electric susceptibility of the structure material ($\chi=\epsilon - 1$). $\mathbf{k}_y$ is the incident wavevector along the NW 