Rainbow trapping and releasing by chirped plasmonic waveguides at visible frequencies

We report on "trapping rainbow" on silver films covered by a one-dimensional chirped dielectric grating. We attribute the trapping effect to correlative dispersive relation between the excited surface plasmon polaritons (SPPs) and the lattice constant of the dielectric grating on the metal film, which results in localization of SPPs of different frequencies at different spatial positions. We further reveal that, by attaching another uniform dielectric grating on the other side of the metal film and real time tuning the refractive index of the grating, the trapped rainbow can be released in sequence. Analytical results are demonstrated by finite-difference time-domain simulation. © 2010 American Institute of Physics.