Extreme optical activity and circular dichroism of chiral metal hole arrays

TL;DR

This paper demonstrates that chiral silver hole arrays exhibit extremely strong optical activity and circular dichroism, functioning as efficient circular polarizers due to chiral plasmonic resonances, with potential applications in polarization control.

Contribution

The study introduces a novel fabrication of chiral metal hole arrays showing unprecedented optical activity and circular dichroism, advancing the understanding of plasmonic chirality effects.

Findings

Achieved polarization rotation up to 90 degrees

Observed full circular dichroism peaks in visible wavelengths

Attributed optical activity to chiral localized plasmonic resonances

Abstract

We report extremely strong optical activity and circular dichroism exhibited by subwavelength arrays of four-start-screw holes fabricated with one-pass focused ion beam milling of freely suspended silver films. Having the fourth order rotational symmetry, the structures exhibit the polarization rotation up to 90 degrees and peaks of full circular dichroism and operate as circular polarizers within certain ranges of wavelengths in the visible. We discuss the observations on the basis of general principles (symmetry, reciprocity and reversibility) and conclude that the extreme optical chirality is determined by the chiral localized plasmonic resonances.