  A method for the substantial reduction of propagation loss of surface
plasmons was proposed and experimentally demonstrated. The method is based on
the fact that the propagation loss of the surface plasmons depends
significantly on the optical confinement of the plasmon. A plasmonic structure,
which contains a metal and two dielectric layers of different refractive
indexes, is proposed in order to optimize optical confinement and to reduce
propagation loss of the surface plasmons. A low propagation loss of 0.17 dB/um
for a surface plasmon in a Fe/MgO/AlGaAs plasmonic structure was achieved. A
good coupling efficiency of 2.2 dB/facet between a surface plasmon in
Fe/MgO/AlGaAs and a waveguide mode in AlGaAs/GaAs optical waveguide was
demonstrated.
