Photonics and Plasmonics in 4D Ultrafast Electron Microscopy

Light–matter interactions at the nanoscale are fundamental to the rapidly developing fields of plasmonics and nanophotonics. These fields hold the promise of advancing both the speed of computers along with communications and may also provide methods to create a new generation of ultrasensitive molecular biosensors. While there are a variety of techniques that can provide static images of these devices with suboptical wavelength precision there are only a few that are capable of capturing the ultrafast dynamics of electromagnetic fields interacting with or produced by nanomaterials. In this Perspective, we aim to introduce the reader to the newly developed field of 4D ultrafast electron microscopy (4D UEM), which provides a unique window into ultrafast dynamics at the nanoscale. We will describe the basic technique and how internal structural, bulk electronic, and surface near-field dynamics can all be obtained with nanometer and femtosecond resolutions. In addition, we will discuss how a variety of different ultrafast electron microscopes have been used to map the evolution of photonics-related phenomena. Throughout, we discuss the direction of research that will help advance the understanding of light–matter interactions near the atomic scale in both space and time