FDTD simulation of highly refractive metasurface

Metasurfaces refers to an artificial sheet material with sub-wavelength periodicity, and had sparked a general interest in their capability to manipulate electromagnetic (EM) fields at high flexibility. One of metasurfaces’ function is performing generalized refraction and reflection, granting it ability similar to of 3D optical instruments such as prism and lens, but executable at a nanoscale level. Using Finite-Difference Time-Domain (FDTD) algorithm, we had designed a metasurface with its unit cell consisting of four TiO₂ rods of same height and different radius to collimate incoming plane wave with 30° incident angle. The refracted wave propagated in direction normal to the metasurface with transmission power of 86% with respect to source.