Extraordinary optical transmission: Role of the slit width in 1D metallic grating on higher refractive index substrate

Abstract

We present a detailed analysis of the excitation of surface plasmon polaritons (SPPs) and associated extraordinary optical transmission (EOT) when a plane wave is incident at normal on a 1D metallic grating fabricated on higher refractive index GaP substrate. A simple method is introduced to estimate the EOT by measuring the 0th order transmission spectra obtained through the plasmonic grating structures with varying grating slit width for a fixed period and the thickness of the gold (Au) film in which the grating is formed. For an optimum Au film thickness, a slit width of slightly less than half and greater than one-third of the periodicity of 770 nm in the grating device yields a maximum EOT value. Such grating devices support only a fundamental plasmonic mode because the profile/shape of the slit in the grating device is more like a sinusoidal nature. Far-field and near-field modelling results also support the far-field results obtained through the experiment. The optimal grating devices have many applications in real world.