A detector of an invisible carpet cloaking structure

Based on transformation optics, we propose a device to detect the presence of a carpet cloaking structure at near field. By using complementary media, the detective device can optically cancel a certain volume of reflective metal and reveal the hidden medium inside the metal. The detective performance of this device is confirmed by full-wave finite-element simulations. It is shown that the detective device is invisible when there is no carpet cloak in the system, yet it becomes visible with the presence of the carpet cloak. The device works at near field, but the response can be found even at the far field. Furthermore, it is shown that the device can detect both anisotropic and isotropic carpet cloaking structures. The investigation may provide a unique method to detect a carpet cloak and contribute to the design of novel optical devices, such as far field detectors for a nanoscale medium.