2-D FDTD modeling of the Extraordinary Optical Transmission Phenomenon through gold film containing a subwavelength single slit

This article presents a computational-analysis study of the enhanced optical transmission phenomenon found within a thin gold film surface, containing a single subwavelength 1-D slit. The central difference approximation and the Yee algorithm were implemented to discrete classical 2-D space-time Maxwell's Equations throughout the Finite-Difference Time-Domain method and Matlab® software. A single nanoslit air region pierced in gold thin films was lighted under normal modulated Gaussian TMz pulse at wavelength of 300 nm and with a unit amplitude. The computational domain in the xy plane was 1 μm × 1 μm, and the time step was 5 fs. In this work were studied the behavior of the tangential electric field intensity values Ez through a nanoslit, derived from the FDTD computational simulations for twelve different aspect ratios R=t/d. It was shown that the diameter d (120, 150 or 200 nm) and the depth t (50, 100, 200, and 300 nm) of the nanoslit are critical for the coupling of the TMz wave with localized surface plasmons, inside the nanoslit region. In general, it was observed that when diameter d decreases, the extraordinary optical transmission phenomenon does not occur within the nanocavity air region, due to influence of higher order evanescent modes.