Three Dimensional Subwavelength focus by a near-field plate lens

摘要

We implemented the inverse design method to build a thin near-field lens thatcould produce a desired subwavelength focus by manipulating the near fields ofa magnetic dipole source. The flat near-field lens represented by an artificialimpedance surface was fabricated by lumped reactive elements (capacitor andinductor) with spatially varying values. In the experiment a desired annularfocusing spot with a characteristic size nearly three times smaller than thatallowed by the diffraction limit was obtained. Besides high-resolution imaging,the proposed near-field plate could be extended for other interestingapplications, such as wireless power transfer or complex wavefront/beam shaper.