Calculating Nonlocal Optical Properties of Structures with Arbitrary Shape

TL;DR

This paper presents a detailed computational method for calculating the nonlocal optical properties of arbitrarily shaped nanostructures, verified against analytical results and applied to various gold nanostructures to reveal nonlocal effects.

Contribution

The paper provides a comprehensive computational approach for nonlocal optical properties of arbitrary structures, including validation and application to complex nanostructures.

Findings

Nonlocal effects cause anomalous absorption and plasmon blueshifting.

Significant decreases in electric field enhancements occur when including nonlocal effects.

Method successfully applied to various geometries, demonstrating its versatility.

Abstract

In a recent Letter [Phys. Rev. Lett. 103, 097403 (2009)], we outlined a computational method to calculate the optical properties of structures with a spatially nonlocal dielectric function. In this Article, we detail the full method, and verify it against analytical results for cylindrical nanowires. Then, as examples of our method, we calculate the optical properties of Au nanostructures in one, two, and three dimensions. We first calculate the transmission, reflection, and absorption spectra of thin films. Because of their simplicity, these systems demonstrate clearly the longitudinal (or volume) plasmons characteristic of nonlocal effects, which result in anomalous absorption and plasmon blueshifting. We then study the optical properties of spherical nanoparticles, which also exhibit such nonlocal effects. Finally, we compare the maximum and average electric field enhancements around nanowires of various shapes to local theory predictions. We demonstrate that when nonlocal effects are included, significant decreases in such properties can occur.