Experimental demonstration of birefrigent broadband transformation Luneburg lenses

Transformation optics (TO) has recently become a useful methodology in the design of unusual optical devices, such as novel metamaterial lenses and invisibility cloaks. Here we report the first experimental realization of birefrigent TO designs of Luneburg lens based on lithographically defined metal/dielectric waveguides. Adiabatic variations of the waveguide shape enable control of the effective refractive indices experienced by the TE and TM modes propagating inside the waveguides. We have studied wavelength and polarization dependent performance of the resulting birefrigent TO devices. These novel optical devices considerably extend our ability to control light on submicrometer scales.