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 ~1.2-μm-high and 1-μm-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 (ns ≈1.34) layer of Cytop. DC structures consisting of sineshaped S-bends (having an offset of ~10 μm over a distance of ~20 μm) and ~100-μm-long parallel LR-DLSPPWs with a center-to-center separation of 2 μm are characterized using scanning near-field microscopy. The experimentally obtained values of the propagation length (~400 μm), S-bend loss (~4 dB) and coupling length (~100 μm) are found in good agreement with the numerical simulations, indicating a significant potential of LR-DLSPPWs for the realization of various plasmonic components.
Optics Express, 2013, Vol 21, Issue 7, p. 8799-8807