Towards Reliable Characterization of Materials' Plasmonic Properties using Fabry-Perot Resonance

TL;DR

This paper presents a theoretical and numerical framework for reconstructing plasmon dispersion relations from Fabry-Perot resonances in transmission spectra of plasmonic gratings, enabling reliable, in-situ material characterization.

Contribution

It introduces a novel method to map plasmon dispersion directly from Fabry-Perot resonances in EOT experiments, accounting for aperture effects and modal hybridization.

Findings

Dispersion relations can be reconstructed from FP resonances in EOT spectra.

A correction factor accounts for aperture effects on resonance frequencies.

The method is validated with FEM and FDTD simulations.

Abstract

Accurate characterization of plasmonic materials' dispersion and efficiency remains a key challenge for next-generation nanophotonic devices. Here, we theoretically demonstrate that the plasmon dispersion relation at a metal-dielectric interface can be reconstructed from the resonance peaks of transmission spectra obtained in a series of extraordinary optical transmission (EOT) experiments on plasmonic gratings. A proof-of-concept of direct E-k dispersion mapping is numerically implemented by systematically varying the grating's unit cell size, with each grating serving as a discrete probe in momentum space. The resulting plasmon dispersion curves are derived from the frequencies of Fabry-Perot (FP) resonances localized within subwavelength apertures, scaled by a correction factor that accounts for the interplay between the resonant mechanisms driving enhanced transmission. This factor highlights the aperture's role in mode confinement and resonance shifting, which we examine in both idealized perfect electric conductor (PEC) and realistic dispersive metal regimes. To elucidate eigenstates of the plasmonic system and quantify the modal hybridization within its apertures, we perform a non-Hermitian modal decomposition using the finite element method (FEM) and corroborate it with finite-difference time-domain (FDTD) simulations. The proposed framework enables an angle-insensitive, real-time, and in-situ characterization platform suitable for wafer-scale evaluation of established and emerging plasmonic materials.