Excitation of surface plasmon polaritons guided mode by Rhodamine B molecules doped in a PMMA stripe.

In this Letter we show the inclusion of Rhodamine B molecules inside a dielectric-loaded surface plasmon waveguide that enables for a precise determination of its optical characteristics. The principle relies on the coupling of the fluorescence emission of the dye to plasmonic waveguided modes allowed in of the structure. Using leakage radiation microscopy in real and reciprocal spaces, we measure the propagation constant of the mode and as well as its attenuation length.