Terahertz Beam Shaping: Gaussian to Flat-top Beam Conversion Through Tri-layer Metasurface

A flat-top beam is preferred to a normal Gaussian beam for various imaging applications since it provides more uniform illumination over a scene. In this paper, we present a highly efficient tri-layer metasurface lens for terahertz beam shaping, namely Gaussian to flat-top beam conversion. This metasurface includes linear polarization conversion, and a full 2 $\pi$ phase tunability range can be covered by varying the geometry of anisotropic resonators. The required phase profile of the metasurface lens is obtained through the Gerchberg–Saxton (GS) algorithm. Full-wave simulations and analytical results confirm that the incident Gaussian beam is transformed to a flat-top beam.