Narrow optical filtering with plasmonic nanoshells
  Narrow optical band pass filters are widely used in systems with optical processing of information, color displays development and optical computers. We show that such ultra filters can be created by means of nanoparticles which consist of a dielectric sphere and a metallic shell. The components can be adjusted such that there is a remarkable transparency at the desired wavelength range, while a strong absorption takes place outside of this region. 
Y. B. Martynov, R. G. Nazmitdinov, I. A. Tanachev, and P. P. Gladyshev
physics.optics cond-mat.mes-hall