Plasmonic modes of extreme subwavelength nanocavities

TL;DR

This paper explores the unique plasmonic modes in U-shaped subwavelength nanocavities, revealing their potential for enhancing nonlinear optics and active plasmonic devices through discrete mode excitation and strong field enhancement.

Contribution

It introduces a new class of nanocavities supporting discrete even and odd plasmonic modes, with detailed simulations of their spectral and near-field properties.

Findings

Discrete modes observed within the nanocavity.

Strong spectral far-field response predicted.

Significant near-field enhancement at resonance.

Abstract

We study the physics of a new type of subwavelength nanocavities. They are based on U-shaped metal-insulator-metal waveguides supporting the excitation of surface plasmon polaritons. The waveguides are simultaneously excited from both sides of the U by incident plane waves. Due to their finite length discrete modes emerge within the nanocavity. We show that the excitation symmetry with respect to the cavity ends permits the observation of even and odd modes. Our investigations include near and far field simulations and predict a strong spectral far field response of the comparable small nanoresonators. The strong near field enhancement observed in the cavity at resonance might be suitable to increase the efficiency of nonlinear optical effects, quantum analogies and might facilitate the development of active optical elements, such as active plasmonic elements.