Rectifying Metasurface for Harvesting Electromagnetic and Optical Energy

This paper presents a compact rectifying metasurface for integrated electromagnetic and optical energy harvesting by using the transparent dielectric substrate. A mesh-type rectifying unit with high optic-transmittance rate is designed on the upper surface of the substrate while the solar panels serve as the ground plane. The proposed structure enables simultaneous harvesting both electromagnetic and optical energy. At the center frequency of 2.45 GHz, the measured radio frequency (RF) to direct-current (DC) conversion efficiency reaches 57% under an input power of 3 dBm. The metasurface remain stable RF-DC efficiency with and without optical illumination, and it also has polarization-insensitive characteristic. To improve the RF-DC efficiency under the large oblique incidence angle, an air layer is introduced between the transparent substrate and the solar panels. By using the symmetric cross-shaped structure as the unit, the wave impedance of the metasurface is lowered. Simulation results show that the RF-DC efficiency is increased by 15% at an incidence angle of 60°.