Fundamental mechanism underlying subwavelength optics of metamaterials: Charge oscillation-induced light emission and interference

TL;DR

This paper uncovers the fundamental charge oscillation mechanism behind subwavelength light interactions with conducting nanostructures, revealing a universal principle that can guide the design of metamaterial nano-optical devices.

Contribution

It introduces a general model of light coupling to free electron oscillations on structured surfaces, explaining subwavelength phenomena without relying on classical surface plasmon dispersion.

Findings

Charge oscillations induce light emission and interference patterns.

The mechanism is a universal geometrical effect applicable to various structures.

Guidelines for designing metamaterial nano-optical devices are provided.

Abstract

Interactions between light and conducting nanostructures can result in a variety of novel and fascinating phenomena. These properties may have wide applications, but their underlying mechanisms have not been completely understood. From calculations of surface charge density waves on conducting gratings and by comparing them with classical surface plasmons, we revealed a general yet concrete picture about coupling of light to free electron oscillation on structured conducting surfaces that can lead to oscillating subwavelength charge patterns (i.e., spoof surface plasmons but without the dispersion property of classical surface plasmons). New wavelets emitted from these light sources then destructively interfere to form evanescent waves. This principle, usually combined with other mechanisms (e.g. resonance), is mainly a geometrical effect that can be universally involved in light scattering from all periodic and nonperiodic structures containing free electrons, including perfect conductors. The spoof surface plasmon picture may provide clear guidelines for developing metamaterial-based nano-optical devices.