Flipping photons backward: reversed Cherenkov radiation

Charged particles moving faster than light in a medium produce Cherenkov radiation. In traditional, positive index-of-refraction materials this radiation travels forward. Metamaterials, with negative indices of refraction, flip the radiation backward. This readily separates it from the particles, providing higher flexibility in photon manipulation and is useful for particle identification and counting. Here we review recent advances in reversed Cherenkov radiation research, including the first demonstration of backward emission. We also discuss the potential for developing new types of devices, such as ones that pierce invisibility cloaks.United States. Office of Naval Research (Contract No. N00014-06-1-0001)United States. Air Force (Contract No. FA8721-05-C-0002)National Natural Science Foundation (China) (60801005)National Natural Science Foundation (China) (60990320)National Natural Science Foundation (China) (60990322)Hunan University (FANEDD (200950))Natural Science Foundation of Zhejiang Province (ZJNSF (R1080320))Spain. Ministerio de Educación y Ciencia (Ph.D Programs Foundation of MEC (200803351025)

Extraordinary surface voltage effect in the invisibility cloak with an active device inside

The electromagnetic field solution for a spherical invisibility cloak with an active device inside is established. Extraordinary electric and magnetic surface voltages are induced at the inner boundary of a spherical cloak, which prevent electromagnetic waves from going out. The phase and handness of polarized waves obliquely incident on such boundaries is kept in the reflected waves. The surface voltages due to an electric dipole inside the concealed region are found equal to the auxiliary scalar potentials at the inner boundary, which consequently gain physical counterparts in this case

Cylindrical Cloak with Axial Permittivity/Permeability Spatially Invariant

In order to reduce the difficulties in the experimental realizations of the cloak but still keep good performance of invisibility, we proposed a perfect cylindrical invisibility cloak with spatially invariant axial material parameters. The advantage of this kind of TE (or TM) cloak is that only rho and phi components of mu (or epsilon) are spatially variant, which makes it possible to realize perfect invisibility with two-dimensional (2D) magnetic (or electric) metamaterials. The effects of perturbations of the parameters on the performance of this cloak are quantitatively analyzed by scattering theory. Our work provides a simple and feasible solution to the experimental realization of cloaks with ideal parameters