Metalens with mixed catenary-pillar nanostructures for improved focusing efficiency

The discrete nanopillars in conventional metalenses limit their phase modulation continuity, which affects their performance, particularly focusing efficiency. Herein, we propose a novel design approach to improve the focusing efficiency of the metalens by using mixed catenary-pillar nanostructures. The simulations demonstrate that the focusing efficiency of one-dimensional metalens with mixed catenary-pillar nanostructures (1D-MMCPN) is 9 % higher than that of one-dimensional metalens with discrete nanopillars (1D-MDN). After optimization, the focusing efficiency of two-dimensional MMCPN (2D- MMCPN) is increased to 60 %, surpassing the two-dimensional MDN (2D- MDN) by 12 %. Moreover, as phase-change material Ge2Sb2Te5 (GST) is used in metalenses design, 2D- MMCPN has a broad adjustable range of focusing efficiency (∼40 %, ranging from 20 % to 60 %) by varying the crystallinity of GST. This novel approach offers exciting prospects for developing miniaturized devices, including night vision, biosensing, and multispectral imaging.