Angle-resolved cathodoluminescence microscopy on plasmonic crystals.

Controlling electromagnetic modes in nanostructures is vital for developing advanced optical devices. Metal surfaces with periodic structures, so-called plasmonic crystals (PlCs), form band structures of surface plasmon polaritons (SPPs), providing highly controllable confinement of SPPs and conversion to far-field light. Angle-resolved cathodoluminescence (CL) spectroscopy, where emitted light upon electron beam irradiation is analyzed with angle selection, can be combined with electron microscopy to visualize eigenmodes at specific wavenumbers. This method allows not only identifying the optical properties of Bloch modes appearing in PlCs, but also accessing functions emerging by local defects introduced into the lattice. This paper reviews applications of angle-resolved CL spectroscopy to mode analysis in one-dimensional and two-dimensional PlCs, and modified structures such as cavities and waveguides. Furthermore, this paper introduces an application of this method to the analysis of enhanced light emission from a phosphor film integrated in a PlC, where emitter-resonator coupling is visualized at the nanoscale.