High efficiency ultrathin transmissive metasurfaces

Metasurfaces offer unprecedented freedom to manipulate electromagnetic waves at deeply subwavelength scales. However, realizing a highly efficient metasurface, yet simple enough to conceptualize, design, and fabricate, is a challenging task. In this paper, a novel approach is proposed for designing meta-atoms which can achieve full phase control in the range 0–2 π with high efficiency in the transmission mode. In particular, a bilayer meta-atom is designed, exploiting nearly perfect polarization conversion of the two orthogonal transmissions, whose transmission efficiency reaches as high as 85%. The transmission phase control in the circular polarization basis is achieved with the axial rotation of the proposed meta-atom based on Pancharatnam–Berry phase principle. These meta-atoms are then wielded to construct metasurfaces for generating vortex beams carrying orbital angular momentum. The conversion efficiency as high as 75% and a transmission efficiency of 55% are achieved for the realized metasurfaces.