Optical Response of Finite-Thickness Ultrathin Plasmonic Films

TL;DR

This paper investigates the unique optical and magneto-optical properties of finite-thickness ultrathin plasmonic films, highlighting their nonlocal dielectric response, resonance behaviors, and potential for negative refraction in the IR range.

Contribution

It introduces the concept of spatially dispersive dielectric permittivity in ultrathin films and demonstrates how their magneto-optical effects can be tuned through various parameters.

Findings

Frequency dependence of magnetic permeability shows sharp resonance shifts with aspect ratio.

Ultrathin films can exhibit negative refraction in the IR range.

Magneto-optical properties are controllable via composition, quality, and environment.

Abstract

We discuss the optical response peculiarities for ultrathin plasmonic films of finite lateral size. Due to their plasma frequency spatial dispersion caused by the spatial confinement of the electron motion, the film dielectric permittivity tensor is spatially dispersive as well and so nonlocal. Such a confinement induced nonlocality can result in peculiar magneto-optical effects. For example, the frequency dependence of the magnetic permeability of the film exhibits a sharp resonance structure shifting to the red as the film aspect ratio increases. The properly tuned ultrathin plasmonic films of finite lateral size can feature the negative refraction effect in the IR frequency range. We discuss how to control these magneto-optical properties and show that they can be tuned by adjusting the film chemical composition, plasmonic material quality, the aspect ratio, and the surroundings of the film.