Design of retroreflective metasurface for high-purity vortex waves under oblique incidence

This paper proposes a high-efficiency retroreflective metasurface for generating high-purity vortex waves under circularly polarized light oblique incidence. Using spectral convolution and harmonic modulation theories, the design efficiently retroreflects vortex waves at incidence angles of 15°, 30°, and 45° by coupling energy to the −1st-order diffraction mode to suppress specular reflection. Operated at 10 GHz, the metasurface's feasibility is confirmed via ansys hfss simulations and near-field scanning measurements. Discrepancies in mode purity (Δ ≈ 0.4) are attributed to antenna matching, transmission losses, and environmental interference. The design introduces an additional degree of freedom for radar and communication systems, highlighting its potential for multifunctional applications in wide-angle scattering and high-purity vortex wave modulation.