Surface plasmon polariton enhanced photoconductivity of tunnel junctions in the visible

Abstract
We have investigated the influence of surface plasmon polaritons (SPP’s) on the reflection spectra of Ag-Al2O2-Al and Al-AL2O2-Al junctions in the visible range. The SPP’s were excited via sinusoidal grating structures. The SPP photon coupling efficiency was optimized as a function of the grating modulation height and dielectric coatings. For optimum coupling conditions a narrowband photoresponse of up to 60 mV/W into a 100-Ω impedance at 632,8 nm was achieved. The narrowband (3–6 nm wide) photosignal is more than an order of magnitude higher than a broadband background signal. The color sensitivity is varied over the whole visible range with different dielectric coatings.