Near-field focusing plates

Using a modulated grating-like surface, referred to as a near-field focusing plate, we experimentally demonstrate focusing well beyond the diffraction limit. The reported near-field plate achieves a resolution of ap lambda₀/20 at a frequency of 1.027 GHz, where lambda₀ is the free space wavelength. Along with these experimental results, the intrinsic properties of near-field plates are reviewed and a general procedure for designing them is outlined.