Electromagnetic Time Reversal Focusing of Near Field Waves in Metamaterials

We demonstrate selective focusing of electromagnetic energy via electromagnetic time reversal in the near field of a metamaterial.

Precise control of electromagnetic energy on a deeply subwavelength scale in the near field regime is a fundamentally challenging problem. In this letter, we demonstrate selective focusing of electromagnetic energy via electromagnetic time reversal in the near field of a metamaterial. Our analysis begins with fundamental mathematics and then is extended to the experimental realm where focusing in space and time of the magnetic fields in the near field of a 1-Dimensional metamaterial is shown. Under time reversal focusing, peak instantaneous fields at receiver locations are at minimum ∼200% greater than other receivers. We then leverage the strong selective focusing capabilities of the system to show individual and selective powering of light emitting diodes connected to coil receivers placed in the near field of the metamaterial. Our results show the possibility of improving display technologies, near field imaging systems, increasing channel capacity of near field communication systems, and obtaining greater control of energy delivery in wireless power transfer systems.