Figure 2: Angle-resolved spectroscopy of electron-induced light emission.

(a) Schematic of the scanning electron microscope-based system for angle-resolved electron-induced light emission spectroscopy. Electrons impinge on samples through a small hole in a parabolic mirror, which collects and collimates emitted light, the beam being subsequently directed to either a spectrometer or imaging CCD (for simplicity, lenses/mirrors/apertures in these paths are not shown). (b,c) Angular distribution of 800±20 nm light emission induced by electron-beam impact (b) on an unstructured gold surface and (c) at the centre of a 30 μm × 30 μm holographic mask in gold, designed to produce a plane wave 800 nm output beam at θ=30° (the azimuthal angle ϕ being arbitrarily set by in-plane sample rotation beneath the incident electron beam; signals are integrated over a 20 s sampling period).