Absolute Experimental Measurement of Intrinsic Helicity in Elementary Plasmonic Nanostructures
Year: 2026
Type: preprint
Abstract: Helicity is a universal quantity describing the internal rotation of an object or a field. Whether it characterizes fundamental properties such as the spin of elementary particles or leads to practical consequences such as the toxicity or harmlessness of chiral molecules, defining and measuring it is essential. However, this remains ambiguous in the case of chiral photonic systems such as plasmonic nanoparticles or photonic metasurfaces, where contrary to common knowledge, the observation of circularly polarized dependent optical properties is not a relevant measure for the helicity. We demonstrate experimentally and theoretically that the helicity can be rigorously defined and measured in a nanoplasmonics system emitting circularly polarized light after excitation in the near-field by a focused electron beam. In the case of a model system composed of two plasmonic dipoles (Born-Kuhn systems), we show that the helicity of photonic modes takes on a very intuitive form and can be simply measured by symmetrizing the geometry of excitation and detection. The method could be extended to a variety of chiral photonic systems, whose locally enhanced properties make them promising for the engineering of local chirality.
Source: arXiv (Cornell University)
Language: English
Subfield: Atomic and Molecular Physics, and Optics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7162450529