Abstract: Over the last two decades, the exploration of optical phenomena at the nanoscale using electron beams has transitioned from a laboratory novelty to an established field within electron microscopy and optical sciences. This transformation was propelled by key conceptual breakthroughs that elucidated the profound connection between electron spectroscopies and the flourishing of instrumental innovations. The integration of electron-based techniques into nanooptics is now such that it has now extended into the domain of quantum nanooptics.
In my presentation, I will discuss our latest efforts to merge electron and optical spectroscopy through a novel synergy of sub-10 nm electron energy loss spectroscopy (EELS) combined with either light collection (cathodoluminescence, CL) or injection (electron energy gain spectroscopy, EEGS). Initially, I will offer a brief overview of the capabilities afforded by state-of-the-art Scanning Transmission Electron Microscope EELS and CL techniques, addressing their separate applications across diverse fields such as nanophotonics, energy materials or and nanomedicine. Subsequently, I will outline various approaches for correlating CL with extinction or absorption (EELS) signals within a Transmission Electron Microscope, targeting applications in physics and materials science that span plasmonic, photonic, and semiconductor systems. Moreover, I aim to demonstrate that coincident measurements of CL and EELS signals can trace the fate of an excited state at the nanoscale — from its inception to its decay into photons. Time permitting, I will conclude with an exploration of EEGS experiments that capitalize on the synchronicity between electrons and photons. Here, photons derived from a pulsed laser are synchronized with the EELS detector, marrying the spectral resolution of a laser with the spatial resolution of STEM.