On the Excitation and Radiative Decay Rates of Plasmonic Nanoantennas

TL;DR

This paper investigates the excitation and radiative decay rates of plasmonic nanoantennas, revealing that some antennas radiate more efficiently than they can be excited, which impacts their design for various nanophotonic applications.

Contribution

It demonstrates through multipole expansion and simulations that plasmonic nanoantennas can radiate more efficiently than they are excited, challenging assumptions based on electromagnetic reciprocity.

Findings

Certain plasmonic antennas radiate more efficiently than they are excited.

Reciprocity holds, but efficiency asymmetries exist in energy coupling.

Design implications for nanophotonic applications like SERS and quantum state engineering.

Abstract

Plasmonic nanoantennas have the ability to confine and enhance incident electromagnetic fields into very sub-wavelength volumes, while at the same time efficiently radiating energy to the far-field. These properties have allowed plasmonic nanoantennas to be extensively used for exciting quantum emitters-such as molecules and quantum dots-and also for the extraction of photons from them for measurements in the far-field. Due to electromagnetic reciprocity, it is expected that plasmonic nanoantennas radiate energy as efficiently as an external source can couple energy to them. In this paper, we adopt a multipole expansion (Mie theory) and numerical simulations to show that although reciprocity holds, certain plasmonic antennas radiate energy much more efficiently than one can couple energy into them. This work paves the way towards designing plasmonic antennas with specific properties for applications where the near-to-far-field relationship is of high significance, such as: surface-enhanced Raman spectroscopy, strong coupling at room temperature, and the engineering of quantum states in nanoplasmonic devices.