Ultrafast response of surface electromagnetic waves in an aluminum film perforated with subwavelength hole arrays

TL;DR

This study investigates the ultrafast optical response of nanostructured aluminum films with subwavelength holes, revealing a blueshift in transmission bands driven by plasma effects and interference, modeled through electron-phonon dynamics.

Contribution

It provides new insights into the ultrafast dynamics of surface electromagnetic waves in nanostructured aluminum, challenging plasmonic explanations and emphasizing interference effects.

Findings

Observed a pronounced blueshift of the transmission band.

Identified the role of plasma attenuation in optical response.

Modeled transient spectra using electron-phonon relaxation dynamics.

Abstract

The ultrafast dynamics of surface electromagnetic waves photogenerated on aluminum film perforated with subwavelength holes array was studied in the visible spectral range by the technique of transient photomodulation with 100 fs time resolution. We observed a pronounced blueshift of the resonant transmission band that reveals the important role of plasma attenuation in the optical response of nanohole arrays. The blueshift is inconsistent with plasmonic mechanism of extraordinary transmission and points to the crucial role of interference in the formation of transmission bands. The transient photomodulation spectra were successfully modeled within the Boltzmann equation approach for the electron-phonon relaxation dynamics, involving non-equilibrium hot electrons and quasi-equilibrium phonons.