Extraordinary Infrared Transmission Resonances of Metal Microarrays for Sensing Nanocoating Thickness

Abstract

Nanocoatings of TiO2 (60−105 nm in thickness) were applied to one side of freestanding Ni films with microarrays of subwavelength holes exhibiting the extraordinary transmission effect in the infrared. Shifts, attenuation, and broadening of the transmission resonances at perpendicular incidence have been observed versus coating thickness. The Ni microarrays exhibit potential as sensors for nanoscale coating thickness and dielectric properties, all of which are accomplished simply by placing mesh in the sample region of an FTIR spectrometer in transmission mode, at perpendicular incidence, without any angle tuning. A second order relation between resonance shifts and coating thickness has been developed which accounts for the effect of changing wavelength of this configuration. A framework is developed for converting these results to momentum space allowing comparison with surface plasmon attenuated total reflection experiments. This exercise illuminates the need for better theoretical models of radiation damping on mesh.