Fig. 9
Numerical simulation of three types of metalenses. Schematics of (a) plasmonic waveguide coupler (PWC) metalens (b) metamaterial immersion lens (MIL) and (c) hyperbolic gradient-index (GRIN) metalens [121]. A normal plane wave is focused by using metalens composed of an Ag PWC and (d) an elliptical dispersion material, and (e) a hyperbolic metamaterial [118]. f Focusing of a normal incident plane wave using a MIL. Permittivity in the direction parallel to the incident is negative, while permittivity in the lateral direction is positive [119]. g Focusing of a normal incident plane wave using hyperbolic GRIN metalens. Electrical intensity distribution is represented by colors. The left inset shows the zoom-in focus area when the metalens is truncated at its internal focal plane [120]