Transformation media that turn a narrow slit into a large window
  Based on the transformation media theory, the authors propose a way to replace a wide window with a narrow slit filled with designed metamaterial to achieve the same transmittance as the one of the window. Numerical simulations for a two dimensional case are given to illustrate the ideas and the performance of the design. 
Xiaohe Zhang, Huanyang Chen, Xudong Luo and Hongru Ma