A Noninterleaved Dual-Band Janus Metasurface With Four Bidirectional Wavefront Control Channels for Vortex Beam Generation

We propose and experimentally validate a non-interleaved, dual-band Janus metasurface that multiplexes frequency and incidence direction to realize four bidirectional and mutually independent wavefront-control channels. The unit cell comprises two layers of rotatable double-split rings and a central polarization-selective grating, enabling 0/π phase coding at 26 GHz and 40 GHz for forward (+z) and backward (−z) incidence, respectively. Based on this design, a 30 × 30-cell prototype generates four OAM beams with topological charges +1, +2, +3, +4. Full-wave simulations and microwave-chamber measurements yield mode purities of 0.72-0.77 (sim.) and 0.62-0.70 (meas.), with inter-channel isolation better than −22 dB and an aperture-level transmission efficiency 0.48. Furthermore, The non-interleaved bidirectional multiplexing achieves 100% spatial utilization without interleaving, offering a compact route to multi-functional, OAM links and multi-target detection.