Compact wavelength add-drop multiplexers using Bragg gratings in coupled   dielectric-loaded plasmonic waveguides
  We report a novel design of a compact wavelength add-drop multiplexer utilizing dielectric-loaded surface plasmon-polariton waveguides (DLSPPWs). The DLSPPW-based configuration exploits routing properties of directional couplers and filtering abilities of Bragg gratings. We present practical realization of a 20-$\mu$m-long device operating at telecom wavelengths that can reroute optical signals separated by approximately 70 nm in the wavelength band. We characterize the performance of the fabricated structures using scanning near-field optical microscopy as well as leakage-radiation microscopy and support our findings with numerical simulations. 
Giulio Biagi, Jacek Fiutowski, Ilya P. Radko, Horst-G\"unter Rubahn,   Kjeld Pedersen, and Sergey I. Bozhevolnyi
physics.optics