Terahertz isotropic transmissive metasurfaces for generation of different wavefronts

Metasurfaces are highly advantageous in realizing the phase discontinuity of an electromagnetic wave. Aiming at manipulating electromagnetic wavefront in terahertz band, a subwavelength multilayer meta-atom is designed, and it is composed of gold mesh, gold disk, and polyimide. By varying the diameter of the central gold disk, eight meta-atoms are prepared to provide full phase modulation with phase increase of 45°. A series of transmissive metasurfaces consisting of these meta-atoms are designed with different arrays. They achieve generations of deflection, single-focusing, dual-focusing, and orbital angular momentum with and . It is noteworthy that metasurfaces assembled by these isotropic meta-atoms are polarization-insensitive. Our models are numerically verified, and all results are consistent with theoretical predictions. Different from reflective metasurfaces that sometimes encounter feeding blockage, transmissive metasurfaces are feasible for the realization of a more compact terahertz system.