Inverse Transformation Optics and Reflection Analysis for Two-Dimensional Finite-Embedded Coordinate Transformation

Inverse transformation optics is introduced, and used to calculate the reflection at the boundary of a transformation medium under consideration. The transformation medium for a practical device is obtained from a 2-D finite-embedded coordinate transformation (FECT), which is discontinuous at the boundary. For an electromagnetic excitation of particular polarization, many pairs of original medium (in a virtual space V´) and inverse transformation can give exactly the same anisotropic medium through the conventional procedure of transformation optics. Nonuniqueness of these pairs is then exploited for the analysis and calculation of the boundary reflection. The reflection at the boundary of the anisotropic FECT medium (associated with the corresponding vacuum virtual space V) is converted to the simple reflection between two isotropic media in virtual space V´ by a selected inverse transformation continuous at the boundary. A reflectionless condition for the boundary of the FECT medium is found as a special case. The theory is verified numerically with the finite element method.