Planar chiral nanoantenna for excitation-chirality-controlled hot spot modulation and emitter-coupled circularly polarized emission

TL;DR

This paper presents a planar chiral nanoantenna design that enables dynamic control of hot spots and circularly polarized emission through excitation chirality and geometric asymmetry, advancing nanoscale chiral photonics.

Contribution

It introduces a broadly applicable framework for engineering chiral nanoantennas with controllable near-field hot spots and emitter polarization, based on mode interference and geometrical design.

Findings

Hot spot can be turned on/off by changing excitation handedness.

Near-field dissymmetry factor peaks at about -2 at 842 nm.

Hot spot intensity can be modulated up to nearly 100% by ellipticity and handedness.

Abstract

A planar chiral plasmonic nanoantenna exhibiting an excitation-chirality-dependent hot spot in a nanogap is numerically investigated. Additionally, the underlying design principles are examined, providing a broadly applicable framework for engineering chiral nanoantennas through controlled geometrical or modal asymmetry. The hot spot can be turned on and off by changing the handedness of the exciting circularly polarized light (CPL). This effect stems from the rationally designed interference of plasmonic modes excited by the linearly polarized orthogonal components of CPL. The hot spot exhibits maximal near-field dissymmetry factor (about -2) at a wavelength of 842 nm. The intensity at the hot spot can also be continuously modulated by varying the excitation ellipticity and handedness, approaching a modulation depth of 100%. These attributes enable chirality- and ellipticity-dependent switching and dynamic modulation of the plasmonic near field. Moreover, placing a quantum emitter in the gap generates almost perfectly circularly polarized emission, offering a simple yet effective avenue to realize nanoscale circularly polarized single-photon sources.