Compact and broadband directional coupling and demultiplexing in dielectric-loaded surface plasmon polariton waveguides based on the multimode interference effect

We theoretically, numerically, and experimentally demonstrate that a directional coupling function can be realized with a wide bandwidth (greater than 200 nm) in dielectric-loaded surface plasmon polariton waveguides based on the multimode interference effect. The functional size of the structures is in the range of several micrometers, which is much shorter than traditional directional couplers consisting of two parallel dielectric or plasmonic metallic waveguides. In addition, 1 x 2 beam splitting and demultiplexing function was realized. Such devices with wide bandwidth and small size indicate potential applications in high density lab-on-chip photonic integration and circuits. (C) 2013 AIP Publishing LLC.