Fig. 1.

Schematic illustrations of a the functionality and b interference principle of the proposed kaleidoscopic meta-plexer with arbitrary spin and wavefront controls. Due to the asymmetric CP reflections in each meta-atom, namely, the total absorption and total reflection in the spin-up and spin-down states, the resulting meta-multiplexer realizes the dual functions of low radar cross-section (RCS) for stealth and nondiffractive Bessel-beam wavefront under the CP-wave excitation (left panel of Fig. 1a). The spin-selection feature can also be used to flexibly control the number of beams of multiple vortices with a spiral wavefront under the LP wave illumination (right panel of Fig. 1a). The key to engineering constructive and destructive interferences is to seek a meta-atom that is composed of dual parts that have a 90° propagation phase difference and a ± 90° geometric-phase difference at the two spin states, as illustrated in Fig. 1b