Trapped Rainbow Techniques for Spectroscopy on a Chip and Fluorescence   Enhancement
  We report on the experimental demonstration of the broadband "trapped rainbow" in the visible range using arrays of adiabatically tapered optical nano waveguides. Being a distinct case of the slow light phenomenon, the trapped rainbow effect could be applied to optical signal processing, and sensing in such applications as spectroscopy on a chip, and to providing enhanced light-matter interactions. As an example of the latter applications, we have fabricated a large area array of tapered nano-waveguides, which exhibit broadband "trapped rainbow" effect. Considerable fluorescence enhancement due to slow light behavior in the array has been observed. 
Vera N. Smolyaninova, Igor I. Smolyaninov, Alexander V. Kildishev,   Vladimir M. Shalaev
physics.optics