Triangular-mesh-based FDTD analysis of two-dimensional plasmonic structures supporting backward waves at optical frequencies

In this paper, the periodic analysis of candidate plasmonic topologies for the implementation of left-handed media at optical frequencies is pursued through a triangular-mesh-based finite-difference time-domain (FDTD), equipped with Floquet boundary conditions. The technique is shown to possess excellent convergence and accuracy properties, as opposed to the conventional rectangular-cell-based FDTD. The latter fails to accurately capture the plasmonic resonant modes excited in the lattices under consideration. The studies presented in this paper are particularly aimed at rigorously investigating the possibility of backward-wave propagation in periodic arrays of plasmonic nanoparticles, along with their potential analogy to microwave negative-refractive index transmission-line metamaterials.