Directional coupling in long-range dielectric-loaded plasmonic waveguides

Directional couplers (DCs) based on long-range dielectric-loaded surface plasmon-polariton waveguides (LR-DLSPPWs) operating at telecom wavelengths are studied both numerically and experimentally. The investigated LR-DLSPPWs are formed by similar to 1.2-mu m-high and 1-mu m-wide polymer ridges fabricated atop of 15-nm-thick and 500-nm-wide gold stripes supported by a 288-nm-thick Ormoclear polymer deposited on a low-index (n(s) approximate to 1.34) layer of Cytop. DC structures consisting of sine-shaped S-bends (having an offset of similar to 10 mu m over a distance of similar to 20 mu m) and similar to 100-mu m-long parallel LR-DLSPPWs with a center-to-center separation of 2 mu m are characterized using scanning near-field microscopy. The experimentally obtained values of the propagation length (similar to 400 mu m), S-bend loss (similar to 4 dB) and coupling length (similar to 100 mu m) are found in good agreement with the numerical simulations, indicating a significant potential of LR-DLSPPWs for the realization of various plasmonic components. (c) 2013 Optical Society of America