Angle-resolved cathodoluminescence imaging polarimetry

TL;DR

This paper introduces a technique for measuring the full polarization state of cathodoluminescence emission, enabling detailed analysis of emission mechanisms in nanostructured and bulk materials.

Contribution

The authors develop a method to determine the complete polarization state of cathodoluminescence as a function of emission angle, advancing the capabilities of CL spectroscopy.

Findings

Polarization can be significantly affected by nanoscale structural features.

The technique distinguishes contributions of coherent and incoherent emission.

Large polarization changes are observed with structural handedness and excitation position.

Abstract

Cathodoluminescence spectroscopy (CL) allows characterizing light emission in bulk and nanostructured materials and is a key tool in fields ranging from materials science to nanophotonics. Previously, CL measurements focused on the spectral content and angular distribution of emission, while the polarization was not fully determined. Here we demonstrate a technique to access the full polarization state of the cathodoluminescence emission, that is the Stokes parameters as a function of the emission angle. Using this technique, we measure the emission of metallic bullseye nanostructures and show that the handedness of the structure as well as nanoscale changes in excitation position induce large changes in polarization ellipticity and helicity. Furthermore, by exploiting the ability of polarimetry to distinguish polarized from unpolarized light, we quantify the contributions of different types of coherent and incoherent radiation to the emission of a gold surface, silicon and gallium arsenide bulk semiconductors. This technique paves the way for in-depth analysis of the emission mechanisms of nanostructured devices as well as macroscopic media.