Conformal transparency

Abstract

Transformation optics (TO) give us an intuitive way to understand the behavior of electromagnetic wave in materials and has been a powerful tool to control light propagation since the two pioneering papers on invisibility in 2006. In the past decade, conformal transformation optics, as a special theory of TO in two dimensions, has extremely enriched the method to manipulate light propagation, which only requests materials with isotropic refractive index distribution, comparing to general TO which usually requires materials with complex electromagnetic property. Recently, the engineering problems of conformal transformation optics has been also discussed. As an important factor, the range of refractive distribution usually hampers experimental realization and application of conformal transformation optics. Furthermore, most proposed devices so far have had imperfect impedance matching at a certain boundary, which results in incomplete invisibility functionalities. In this talk, we would like to introduce a Mikaelian lens to design a new conformal transparent device. The Mikaelian lens has a self-focusing property for parallel light rays. By using a conformal logarithmic mapping with a linear term, the maximum of refractive index of this device is deduced to about five, which is close to current experimental techniques for microwave and terahertz. We hope that our work will bring in a proof-of-principle experiment of conformal transformation optics soon. Moreover, this transparent device can hide a perfect electrical conduct (PEC) line from all angle, which is quite different from carpet cloaking. By further introducing a general transformation method, we can expand the linear PEC to create cloaking regions.