Imaging Photonic Resonances within an All-Dielectric Metasurface via Photoelectron Emission Microscopy

Dielectric metasurfaces exploit light-matter interactions and symmetry to manipulate light for next generation optical devices. Here, we use photoelectron emission microscopy (PEEM) to demonstrate near-field, nanoscale imaging of optical resonances within a dielectric metasurface in the visible wavelength range excited by far-field illumination. The metasurface supports two distinct resonances occupying areas of different material thickness, resulting in contrast in photoemission intensity due to the photoelectron inelastic mean free path (IMFP). Through analysis comparing PEEM images to simulations, we determine the IMFP of very low energy (<1 eV) photoelectrons to be ~35 nm (comparable to meta-atom height), highlighting sensitivity of PEEM to the volume. These results demonstrate that photoelectron imaging is suitable for examining light-matter interactions in volume-type (as opposed to surface) photonic modes within dielectric nanophotonic structures.