Reconfigurable Planar Metasurface Lens using TiO2: Design and Simulation

A reconfigurable plasmonic metasurface lens using TiO2 thin film is designed and simulated. Such a planar lens consists of an array with gold nano-antennas mounted on an uniaxial anisotropic substrate. The element of this array is a class of V-shaped nano-antenna with two freedom degrees for extracting phase diagram needed for plasmonic lens design. Two different parameters of this element are the length V arms and its angle. The used Titanium dioxide (TiO2) as a substrate of this metasurface leads to adding another freedom degree into the unit cell due to its anisotropy property at optical regime. Such a unit cell is analyzed using Method of Moments (MoM) in which its dyadic Green's function is evaluated by means of the Equivalent Transmission Line Model (ETLM). Using MoM/ETLM, the cross-polar phase diagram of unit cell is extracted once the optical axis of anisotropic thin film is aligned in x-direction. Then, the elements' dimensions of the lens's array is selected by means of the obtained phase diagram and the equal optical length principle to fulfill the required phase discontinuities of each cell and produce double focus points. Finally, the entire of structure is simulated using a Finite Element Method (FEM) based simulator. It is numerically shown that a double focus planar lens is achieved once lens surface is illuminated by a plane wave and the intensity of lens focuses can be controlled by rotation of TiO2 optic axis. Such a controllable behavior can also be achieved by changing the incident polarization.