High-Efficiency Plasmonic Metalens for Dual-Polarization Imaging with a Single Set of 3D Variable Nanostructures

We propose and experimentally demonstrate a new type of nanostructures in which the height of each meta-atom varies in addition to variations of in-plane dimensions of the meta-atom. A dual-polarization plasmonic metalens (DPPM) with a single set of three-dimensional variable nanobrick array is demonstrated. An incident light with 0 & DEG; and 90 & DEG; orthogonal linear polarization (LP) states can be split and simultaneously focused at different positions by the proposed DPPM, which breaks the 50% energy efficiency limit of conventional polarizers. The DPPM consisted of an array of Au layer-covered anisotropic polymethyl methacrylate nanobricks with not only different lengths/widths but also heights, from which the desired full-phase (0-2 pi) and high reflecting coefficient (> 0.9) can be achieved simultaneously by the coupling of nanocavity with different cavity heights and localized surface plasmons. Experimental results show that optical resolution of the fabricated DPPM is very close to the diffractive limit, and the average LP extinction ratio reaches & SIM;10 dB within the band of 1300-1600 nm. The work demonstrates the feasibility of introducing the height of each meta-atom as a new degree of freedom to achieve high-performance optical functions with high efficiency and is useful in polarization-dependent imaging, optical communications, and various endoscope detections.