Ultrasmall volume Plasmons - yet with complete retardation effects

TL;DR

This paper explores how ultrasmall plasmonic particles within band-gap media can exhibit complete retardation effects, leading to resonances with significantly enhanced quality factors due to wave interference.

Contribution

It demonstrates the existence of full retardation effects in deep subwavelength plasmonic resonators, challenging the quasi-static approximation and revealing new resonance mechanisms.

Findings

Resonance Q-factor increased to 50 from 5.5 in deep subwavelength regime

Wave interference effects enable full retardation in ultrasmall particles

Band-gap media act as wave-mirrors, facilitating constructive interference

Abstract

Nano particle-plasmons are attributed to quasi-static oscillation with no wave propagation due to their subwavelength size. However, when located within a band-gap medium (even in air if the particle is small enough), the particle interfaces are acting as wave-mirrors, incurring small negative retardation. The latter when compensated by a respective (short) propagation within the particle substantiates a full-fledged resonator based on constructive interference. This unusual wave interference in the deep subwavelength regime (modal-volume<0.001lambda^3) significantly enhances the Q-factor, e.g. 50 compared to the quasi-static limit of 5.5.