(a) Leakage radiation image of SPPs from a plasmonic demultiplexer based on concentric grooves. Insets show the enlarged area of the SPP waveguides. Reprinted from reference [29] with permission. (b) Schematic of a plasmonic demultiplexer based on diffracting slits. (c) Leakage radiation image shows SPPs are routed to different positions with incident light of different wavelengths. Reprinted from reference [81] with permission.