Fig. 1. (a) FDTD simulation of normalized Poynting vector S_z for designed metallic nano-slit lens. Film thickness is 500 nm, and the total number of slits is 65. (b) Geometry of the metalens (left) with 400 nm optically thick gold film with air slits of varying widths milled on a fused silica substrate (dark blue). Inset: SEM image of air slits. Measured (center) and simulated (right) focusing pattern at the design wavelength of 637 nm. (c) SEM image of the fabricated lens with 3 cm focal length (left). The corresponding phase shift profile (right) is radially discretized according to the phase shifts of the eight antennas. Insets: close-ups of patterned antennas. (d) SEM image of plasmonic metalens on glass substrate with negative polarity (top left) and positive polarity (top right) for incident light with RCP. Expected phase shift by positive (middle) and negative (bottom) lens, for RCP incident light. (e) (i) Focal spot intensity distribution of the reflected beam in the x–z plane, with antenna arrays centered at x = 0. (ii) Most of the reflected light beam in far-field projection was focused at 0°, normal to the metalens surface. Simulation and experimental results of (iii) angular scan and (iv) translational scan of the normalized reflected beam intensity at the focus. (a) Reprinted with permission from ref. 38. Copyright 2005 The Optical Society. (b) Reprinted with permission from ref. 39. Copyright 2008 American Chemical Society. (c) Reprinted with permission from ref. 41. Copyright 2012 American Chemical Society. (d) Reprinted with permission from ref. 44. Copyright 2012 Nature Publishing Group. (e) Reprinted with permission from ref. 49. Copyright 2016 The Optical Society.