Transformation bending device emulated by graded-index waveguide
  We demonstrate that a transformation device can be emulated using a gradient-index waveguide. The effective index of the waveguide is spatially varied by tailoring a gradient thickness dielectric waveguide. Based on this technology, we demonstrate a transformation device guiding visible light around a sharp corner, with low scattering loss and reflection loss. The experimental results are in good agreement with the numerical results. 
Y. Wang, C. Sheng, H. Liu, Y. J. Zheng, C. Zhu, S. M. Wang, and S. N.   Zhu
physics.optics