A Subwavelength Focusing Structure Composite of Nanoscale Metallic Slits Array With Patterned Dielectric Substrate

A novel plasmonic lens consisting of metallic nanoslits with a patterned dielectric substrate is proposed. In the structure, all metallic nanoslits have the same geometrical parameters and interspacing. The phase of incident light is modulated beforehand by the substrate before they bump on the metal slits. The surface plasmon polaritons (SPPs) wave excited by the modulated light will be focused after passing through the slits. Numerical simulation demonstrates that the size of the generated focal spot is very close to half wavelength. The overriding advantage of the proposed structure is that it significantly reduces the difficulty in fabrication while the focusing properties are comparable to the ones with filling materials in the slits.