The vertical distribution of the electric field enhancement produced by optical antennas could be experimentally confirmed. The combination of the antenna and a quantum cascade laser would yield attractive mid-infrared microscopic analysis to detect a solid state surface. In this work, slot antenna arrays were formed on a thin Al2O3 layer grown by atomic layer deposition on a silicon substrate. Reflectivity spectra measured in the mid-infrared range showed characteristic aspects, presumably caused by the surface phonon polariton of a SiO2 layer naturally formed on the Si substrate. When the Al2O3 layer thickness was 6 nm, such spectral features disappeared. In this way, we could estimate experimentally the electric field distribution normal to the surface of the substrate.

Copper oxide --- Catalyst --- XAFS --- Electron yield detection