Tunable Localization and Oscillation of Coupled Plasmon Waves in Graded Plasmonic Chains

TL;DR

This paper investigates how coupled plasmon waves in graded nanoparticle chains can be localized and made to oscillate, revealing conditions for specific oscillation behaviors useful for optical device design.

Contribution

It introduces the concept of plasmonic gradons in graded chains and analyzes their localization and oscillation dynamics, highlighting conditions for Bloch oscillations.

Findings

Localization of plasmon modes depends on the grading profile.

Oscillation behaviors vary with different gradon types.

Certain gradons enable Bloch oscillations in graded chains.

Abstract

The localization (confinement) of coupled plasmon modes, named as gradons, has been studied in metal nanoparticle chains immersed in a graded dielectric host. We exploited the time evolution of various initial wavepackets formed by the linear combination of the coupled modes. We found an important interplay between the localization of plasmonic gradons and the oscillation in such graded plasmonic chains. Unlike in optical superlattices, gradient cannot always lead to Bloch oscillations, which can only occur for wavepackets consisting of particular types of gradons. Moreover, the wavepackets will undergo different forms of oscillations. The correspondence can be applied to design a variety of optical devices by steering among various oscillations.