Broadband Transformation Optics Devices
  Recently we have suggested that two-dimensional broadband transformation optics devices based on metamaterial designs may be built using tapered waveguides. Here we review application of this principle to broadband electromagnetic cloaking, trapped rainbow, and novel microscopy devices. 
Vera N. Smolyaninova, Igor I. Smolyaninov, Alexander V. Kildishev, and   Vladimir M. Shalaev
physics.optics