The Physics of Unbounded, Broadband Absorption/Gain Efficiency in Plasmonic Nanoparticles

TL;DR

This paper reveals how specific plasmonic nanostructures can theoretically achieve infinite broadband absorption and gain efficiencies due to anomalous resonances, with potential applications in nonlinear optics, sensing, and energy harvesting.

Contribution

It provides a closed-form analytical solution explaining the physics behind broadband anomalous resonances in shaped plasmonic nanoparticles, highlighting their potential for high-efficiency applications.

Findings

Analytical solution for fields scattered by conjoined semicircles.

Fundamental physics of broadband adiabatic focusing of surface plasmons.

Justification of finite absorption/gain with infinitesimal material loss/gain.

Abstract

Anomalous resonances in properly shaped plasmonic nanostructures can in principle lead to infinite absorption/gain efficiencies over broad bandwidths. By developing a closed-form analytical solution for the fields scattered by conjoined semicircles, we outline the fundamental physics behind these phenomena, associated with broadband adiabatic focusing of surface plasmons at the nanoscale. We are able to justify the apparent paradox of finite absorption/gain in the limit of infinitesimally small material loss/gain, and we explore the potential of these phenomena in nonlinear optics, spasing, energy-harvesting and sensing.