(a) Schematic of meta-atom design and picture of part of a fabricated CP Bessel beam generator which is a PB metasurface (left panel) designed based on a particular transmission-phase distribution (right panel). (b) FDTD simulated distribution on the xz plane with y = 0 mm for our metasurface (placed at z = 0 mm) shined by a normally incident x-polarized THz beam at 0.66THz. (c) FDTD simulated and (d) z-scan measured distributions inside the area surrounded by black dashed lines in (b), under exactly the same conditions as in (b). (e) Measured distributions on x-y planes with z=2, 3 and 4 mm, respectively. all figures reproduced from [29].