Tailoring absorption in metal gratings with resonant ultra-thin bridges

TL;DR

This paper theoretically demonstrates how localized resonances in ultra-thin metal bridges within gratings can significantly enhance and tailor absorption, with potential applications in nonlinear optics.

Contribution

It introduces a novel method to manipulate absorption in metal gratings using resonant surface plasmon polaritons in ultrathin bridges, independent of grating periodicity.

Findings

Localized resonances dramatically modify transmission spectra.

Absorption can be tailored regardless of aperture size.

Enhanced absorption may boost nonlinear optical processes.

Abstract

We present a theoretical analysis of the effects of short range surface plasmon polariton excitation on sub-wavelength bridges in metal gratings. We show that localized resonances in thin metal bridges placed within the slit of a free-standing silver grating dramatically modify transmission spectra and boost absorption regardless of the periodicity of the grating. Additionally, the interference of multiple localized resonances makes it possible to tailor the absorption properties of ultrathin gratings, regardless of the apertures' geometrical size. This tunable, narrow-band, enhanced-absorption mechanism triggered by resonant, short range surface plasmon polaritons may also enhance nonlinear optical processes like harmonic generation, in view of the large third-order susceptibility of metals.