Cathodoluminescence Wavefront Retrieval

TL;DR

This paper introduces a reference-free phase retrieval method for cathodoluminescence wavefronts using the Gerchberg-Saxton algorithm, enabling detailed analysis of optical excitations in nanostructures.

Contribution

It presents a novel, reference-free approach for reconstructing the phase of cathodoluminescence wavefronts in nanostructures, enhancing nanoscopy capabilities.

Findings

Successfully reconstructed phase distributions for various nanostructures.

Revealed underlying radiation mechanisms through phase analysis.

Demonstrated robustness and flexibility of the method.

Abstract

Free-electron-based nanoscopy enables the study of optical excitations in materials with deep-subwavelength spatial resolution, with cathodoluminescence (CL) being one of the resulting radiation signals. When combined with an optical collection system, CL measurements can access multidimensional information of light; yet the phase of the emitted optical fields has remained largely elusive. Here, we demonstrate a reference-free phase retrieval approach for far-field CL wavefronts using the Gerchberg-Saxton algorithm implemented with real-space and angular-space CL intensity data. Applying this approach to representative nanostructures, including a planar surface, nanosphere, plasmonic crystal, and nanowire, we reconstruct distinct phase distributions that reveal their underlying radiation mechanisms. This reference-free framework offers a robust and flexible route for retrieving the phase of electron-beam-excited optical fields without relying on a reference wave, making it readily extendable to a wide range of nanostructures.