Fig. 3
SEM image of an hexagonal lattice of pores on the diatom surface reproducing a photonic crystal (a). Pore size, shape, and topology of the real prototype, and random patterns of gold NPs distributed between the pores, were replicated in a numerical finite element analysis (FEA) tool-box (b). The output of the simulations is the EM field and the EM field enhancement around the aggregates of gold nanoparticles, with a maximum EM field of nearly ~3 108 V/m (c). EM distribution shows sensitivity to the orientation of the pore surface with respect to the external incident radiation (d). Varying the angle of incidence between the external radiation and the normal of the pore surface over significant intervals, we find that the maximum EM field intensity oscillates between ~1.5 108 and ~4 108 V/m (e)