Nanorod optical antennas for dipolar transitions

TL;DR

This paper presents an analytical model for metal nanorod optical antennas, explaining how they interact with dipolar transitions and how their modes evolve with plasmonic properties, providing insights for designing efficient antennas.

Contribution

It introduces a phase-matching analytical model for nanorod antennas, elucidating mode evolution and interaction with dipolar emitters, applicable to a wide range of nanorod-light interactions.

Findings

Antennas should not be overly plasmonic for efficiency.

Subradiant modes can evolve into dark modes with weak interaction.

The model accurately describes the complete emission process.

Abstract

Optical antennas link objects to light. Here, we analyze metal nanorod antennas as cavities with variable reflection coefficients to derive the interaction of dipolar transitions with radiation through the antenna modes. The presented analytical model accurately describes the complete emission process, and is summarized in a phase-matching equation. We show how antenna modes evolve as they become increasingly more bound, i.e. plasmonic. The results illustrate why efficient antennas should not be too plasmonic, and how subradiant even modes can evolve into weakly-interacting dark modes. Our description is valid for the interaction of nanorods with light in general, and is thus widely applicable.