Unlimited-Power Reflectors, Absorbers, and Emitters with Conjugately   Matched Layers
  In order to ensure the fastest wireless energy transfer from a source to the user one needs to maximize the channel capacity for power transport. In communications technologies, the concept of MIMO (multiple input, multiple output) exploits the idea of sending signals via many different rays which may reach the receiver. However, if we are concerned with the task of energy transfer, still only one mode is exploited, even if multiple antennas are used to send power to the receiver. In the near-field scenario, this is the magnetic dipole mode of receiving coil antennas. In the far-field scenario, this is the propagating plane wave TEM mode. Recently, it was shown that using special artificial materials it is possible to ensure that all electromagnetic modes of free space are conjugately matched to the modes of a material body and, thus, all modes deliver power to the body in the most effective way. Such a fascinating feature is acquired because the conjugate matching does not concern only the propagating modes but, most importantly, is applied to all evanescent modes. However, coupling to higher-order (mostly evanescent) modes is weak and disappears in the limit of an infinite planar boundary. We show that properly perturbing the surface of the receiving or emitting body with, for example, randomly distributed small particles we can open up channels for super-radiation into far zone. The currents induced in the small particles act as secondary sources which send the energy to travel far away from the surface and, reciprocally, receive power from far-located sources. We theoretically predict about 20-fold power transfer enhancement between the conjugately matched power-receiving body (as compared with the ideal black body) and far-zone sources. Reciprocally, the proposed structure radiates about 20 times more power into far zone as compared with the same source over a perfect reflector. 
Constantinos A. Valagiannopoulos and Sergei A. Tretyakov
physics.class-ph cond-mat.mes-hall physics.optics