Diverse terahertz wavefront manipulations empowered by the spatially interleaved metasurfaces

Optical metasurfaces have advanced approaches for manipulating light information in the spatial domain, in which the spatially interleaved metasurfaces demonstrate the ability to manipulate a more complex wavefront of light than metasurfaces without the spatial interleaving. The potential of the spatially interleaved metasurfaces has not been fully exploited. In this paper, we design the spatially interleaved terahertz (THz) metasurfaces based on the ingenious spatial interleaving principles to develop the diverse THz wavefront manipulations. Four functions are performed, including the orbital angular momentum (OAM) superposition of single-frequency vortex beams, the separate vortex focusing of single-frequency dual beams, the different OAM manipulations of bifrequency beams in different planes, and achromatic focusing. The demonstrated functions prove that the spatially interleaved metasurface can manipulate THz wavefront at both single frequency and bifrequency, which traditional metasurfaces cannot. This work paves the way for diverse THz wavefront manipulations.