Description of dispersion properties of metals by means of the critical points model and application to the study of resonant structures using the FDTD method

Using a combination of Drude and critical points models, we show that the permittivity of several metals can be more efficiently described than using the well-known Drude-Lorentz model. The numerical implementation in a finite- difference time-domain code together with a non-uniform grid enables the study of thin metallic intermediate layers often neglected in simulations but found in realistic resonant structures.