(18) C. T. Chan
Hong Kong University of Science and Technology, Hong Kong, China.

Title: Transformation optics using rotated and folded geometries

Abstract:

Transformation optics establishes a correspondence between coordinate transformation and a transformation of material constituent parameters.
Interesting optical illusion effects such as invisibility cloaking can be achieved by a radial transformation in spherical coordinates. We will extend the idea to other kinds of transformation. We introduce a rotation mapping of coordinates that can be realized by a specific transformation of the permittivity and permeability of a shell surrounding an enclosed domain. This kind of transformation media rotates the information for a fixed angle, so that observers inside/outside the rotation coating would see a rotated world with respect to each other, and the existence of the shell is not detectable.
Various reduced form of implementation is considered, including a layered system involving alternating layers of metals and dielectrics.
Experiments in the microwave regime were carried out to demonstrate the rotation effect happens in a broad frequency range. We consider extending the idea of cloaking to acoustic waves. In two dimensions, the solution is readily obtained by mapping the acoustic equations to the Maxwell’s equations of one polarization in the 2D geometry. We find that the acoustic equation can be mapped to the DC conductivity equation in 3D, which then allows the design of 3D acoustic cloaking using the coordinate transformation scheme. The perfect cloaking effect of such a cloak is confirmed by solving for the scattering problem using the spherical-Bessel function series expansion method. We will also discuss other issues such as the possibility of extending the bandwidth of the invisibility cloak, the energy transport velocity inside the cloak and whether the invisibility cloak based on transformation media can really hide everything inside.