Metafilm focusing incident plane waves for energy harvesting

An ultrathin, composite metafilm consisting of gradient-index TE- and TM-type metasurfaces for high power electromagnetic energy harvesting applications is demonstrated. The proposed metafilm possesses the sinusoidal index-modulation property, which can convert incident plane waves (PWs) into surface waves (SWs) that concentrate to the center with high intensity and could be harvested by a single rectifier. Without the requirement of the increasing number of rectifiers and feed networks as commonly utilized in array-type rectennas or metasurfaces, a feasible amount of harvested power can be achieved by simply enlarging the film dimensions, and thereby, high SW to DC conversion efficiency is guaranteed. The results show that the harvested power would be increased from 4.1 μW to 73 μW by enlarging the panel dimensions from that containing 19 × 19 cells to 81 × 81 cells.