  Two-dimensional plasmonic demultiplexers for surface plasmon polaritons
(SPPs), which consist of concentric grooves on a gold film, are proposed and
experimentally demonstrated to realize light-SPP coupling, effective dispersion
and multiple-channel SPP guiding. A resolution as high as 10 nm is obtained.
The leakage radiation microscopy imaging shows that the SPPs of different
wavelengths are focused and routed into different SPP strip waveguides. The
plasmonic demultiplexer can thus serve as a wavelength division multiplexing
element for integrated plasmonic circuit and also as a plasmonic spectroscopy
or filter.
