Optimal conditions for detecting optical dichroism at the nanoscale by electron energy-loss spectroscopy

TL;DR

This paper theoretically investigates how to optimally detect optical circular dichroism at the nanoscale using electron energy-loss spectroscopy with orbital angular momentum, providing insights for future experimental applications.

Contribution

It offers a detailed theoretical analysis of the optimal parameters for detecting dichroism via OAM-resolved EELS in chiral nanostructures, a novel approach in the field.

Findings

Identifies optimal conditions for EELS-based dichroism detection.

Provides insights into the interpretation of OAM-resolved EELS signals.

Guides future experimental efforts in nanoscale optical chiroptical analysis.

Abstract

The emergence of optical circular dichroism in chiral nanoscale and molecular systems provides not only a way for analyzing the sample chirality itself but also additional degrees of freedom in manipulating light. Such manipulation can be reached even at the nanoscale level; however, probing and understanding the properties of optical fields well below the diffraction limit requires an adequate technique. Electron energy-loss spectroscopy (EELS) with orbital angular momentum (OAM)-based electron state sorting has been suggested as a suitable candidate, but to date, no conclusive experiments have been performed. We, therefore, theoretically explore the emergence of dichroism in EELS for a canonical single-twist helix nanostructure and present a detailed analysis of the optimal parameters to obtain a robust signal. Our work offers novel insights into the interpretation and volatility of the OAM-resolved EELS signal, which can inspire and guide future experimental efforts.