Modulation of Spin Angular Momentum of Emission in Symmetric 1D Plasmonic Crystals by Cathodoluminescence

TL;DR

This study demonstrates that symmetric 1D plasmonic crystals can be used to controllably generate and modulate circularly polarized light through electron beam excitation and interference effects, advancing photonic device design.

Contribution

It introduces a method to modulate circularly polarized emission in symmetric plasmonic structures using electron beam excitation and interference, without requiring chiral design.

Findings

CPL can be generated and modulated in symmetric 1D plasmonic crystals.

Interference effects enable control over CPL dispersion and spatial dependence.

Excitation position influences the efficiency of CPL generation via surface plasmon polariton scattering.

Abstract

The spin angular momentum (SAM) of light has become a cornerstone of numerous photonic applications, including optical communication and chiral photonics. Because SAM is inherently associated with circularly polarized light (CPL), the ability to modulate CPL in a controlled and efficient manner is essential not only for advancing fundamental studies of light-matter interactions but also for enabling next-generation photonic technologies. However, such modulation is commonly realized by structurally chiral systems, which inherently limits the feasibility of dynamic tuning. Here, we demonstrate that one-dimensional plasmonic crystals (1D PlCs), despite their structural symmetry, can serve as a platform for controllable CPL generation. By employing an electron beam in scanning transmission electron microscopy (STEM), we coherently excite transition radiation and emission from 1D PlC modes. Their interference produces energy- and momentum- (emission angle-) resolved CPL, which clearly reveals its dispersion and spatial dependence at the nanoscale, providing direct guidance for its manipulation and offering insights into the design of plasmonic devices including the phase information. Furthermore, interference with surface plasmon polariton scattering at the structural boundary enables the efficiency modulation of CPL generation via the excitation position along the terrace.