All-dielectric subwavelength metasurface focusing lens

TLDR

The lens is fabricated by patterning a dielectric surface into sub‑micron nano‑pillar arrays with variable diameters, creating a gradient‑index metamaterial whose effective optical density peaks at the center and tapers toward the periphery. The resulting micro‑lenses exhibit low reflection, tunable phase gradients, focal lengths of a few hundred microns, a beam area contraction ratio up to three, and insertion losses as low as 11 %.

Abstract

We have proposed, designed, manufactured and tested low loss dielectric micro-lenses for infrared (IR) radiation based on a dielectric metamaterial layer. This metamaterial layer was created by patterning a dielectric surface and etching to sub-micron depths. For a proof-of-concept lens demonstration, we have chosen a fine patterned array of nano-pillars with variable diameters. Gradient index (GRIN) properties were achieved by engineering the nano-pattern characteristics across the lens, so that the effective optical density of the dielectric metamaterial layer peaks around the lens center, and gradually drops at the lens periphery. A set of lens designs with reduced reflection and tailorable phase gradients have been developed and tested, demonstrating focal distances of a few hundred microns, beam area contraction ratio up to three, and insertion losses as low as 11%.