B-CALM: An open-source GPU-based 3D-FDTD with multi-pole dispersion for plasmonics

Numerical calculations with finite-difference time-domain (FDTD) on metallic nanostructures in a broad optical spectrum require an accurate approximation of the permittivity of dispersive materials. Here, we present the algorithms behind B-CALM (Belgium-California Light Machine), an open-source 3D-FDTD solver operating on Graphical Processing Units (GPU's) with multi-pole dispersion models. Our modified architecture shows a reduction in computational times for multi-pole dispersion models for a broad spectral range. We benchmark B-CALM by computing the absorption efficiency of a metallic nanosphere with a one-pole and a three-poles Drude-Lorentz model and compare it with Mie theory.