compact plasmonic lens based on nanoslits in the tree age chart arrangement

A novel plasmonic planar slit lens, consisting of five slits in tree age chart arrangement with gradually decreasing widths and interspace distances, is proposed. the slits width and interspaces are related with each other by introducing a scaling constant k that was previously introduced in nanoparticle chains. at specific k values, the light propagates extraordinarily through the slits and causes focusing features beneath the metallic layer. the underlying physics behind the focusing is because of additional phase imposed on traveling light through the slits and their constructive interference. numerical simulation is used to demonstrate the focusing behavior. results show that the slit width should not be larger than half wavelength, and the scaling constant should be between 0.3 and 0.4. salient features of the proposed structure are ultra-compactness, large transmission, and ease of fabrication.