Light emission from tunnel junctions on gratings

We present measurements of light emission from Al-${\mathrm{Al}}_2$ ${\mathrm{O}}_3$-Ag tunnel junctions on holographically produced, sinusoidal profile gratings. Sharp angle tunable emission peaks result from coupling out of the Ag-vacuum fast surface-plasmon polariton by the grating structure. The dependences of the emission intensities on angle, frequency, bias voltage and current, and grating amplitudes agree well with a recent theory by Laks and Mills [Phys. Rev. B 22, 5723 (1980)]. The absolute intensities and dependence of intensities on Ag-film thickness do not agree as well. We propose a possible explanation for this discrepancy. PACS numbers 1977 73.40.Rw, 78.65.Ez BD2092