Metallic screens for sub-wavelength focusing of electromagnetic waves

Abstract

A method and apparatus for near-field focusing of an incident wave, over a range of frequencies from microwaves to optical frequencies, into a sub-wavelength spot having a peak-to-null beamwidth of λ/10. The screen may be made out of closely spaced, unequal slots cut on a metallic sheet. Nano-scale focusing capability may be achieved with a simple structure of three slots on a metallic sheet, which can be readily implemented using current nanofabrication technologies. Unlike negative-refractive-index focusing implementations, this “meta-screen” does not suffer from image degradation when losses are introduced and is easily scalable from microwave to Terahertz frequencies and beyond. The slotted geometry is designed using a theory of shifted beams to determine the necessary weighting factors for each slot element, which are then converted to appropriate slot dimensions.

Dependencies are inferred from the claim text.