  A quasi-continuous composite perfect electric conductor-perfect magnetic
conductor metasurface and a systematic metasurface design process are proposed
for the orbital angular momentum (OAM) generation. The metasurfaces reflect the
incident left circularly polarized (LCP)/right circularly polarized (RCP) plane
wave to RCP/LCP vortex beams carrying OAM at normal or oblique direction.
Unlike conventional metasurfaces that are composed of discrete scatterers, the
scatterers on the proposed metasurface form a quasi-continuous pattern. The
patterning of the metasurface is calculated through grating vectors, and no
optimization of single scatterer is required. Furthermore, the distortions from
local-response discontinuity of discrete scatterers are avoided. This letter
provides great convenience to high-quality OAM generation.
