Inverse raytracing for metamaterial design

Fermat's principle was used in its inverse way. Needed light path can be designed according to application. So the light rays curvature is known at each point in the space. The proposed method allows to determine numerically the needed value of the index of refraction at each point in the space. Results show that only thin layers with a mixture of positive and negative gradient of the refractive index is needed in the studies applications.