Passive optical elements can play key roles in photonic applications such asplasmonic integrated circuits. Here we experimentally demonstrate passivegap-plasmon focusing and routing in two-dimensions. This is accomplished usinga high numerical-aperture metal-dielectric-metal lens incorporated into aplanar-waveguide device. Fabrication via metal sputtering, oxide deposition,electron- and focused-ion- beam lithography, and argon ion-milling is reportedon in detail. Diffraction-limited focusing is optically characterized bysampling out-coupled light with a microscope. The measured focal distance andfull-width-half-maximum spot size agree well with the calculated lensperformance. The surface plasmon polariton propagation length is measured bysampling light from multiple out-coupler slits.
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