Frequency-dependent refractive index of one-dimensionally structured thick metal film

The authors have studied the frequency-dependent dielectric response of thick metal film one-dimensionally perforated by a subwavelength slit waveguide array. Our theoretical approach based on a three-dimensional homogenization of the periodic metallic structure shows that an effective refractive index chromatically varying due to TE waveguide mode formation gives rise to dense Fabry-Pérot resonance population near the cutoff, which leads to an energy level continuum in the transmission spectrum. Finite difference time domain simulation numerically demonstrates the transmission spectrum and spatial field distributions of even and odd resonance modes.