Broadband reflective wavefront manipulation enabled by a polarization-twisting design method

A simplified design approach for circularly polarized (CP) reflective wavefront-manipulation arrays is presented using rotational polarization-twisting (PT) meta-atoms. It is demonstrated through theoretical analysis that a PT meta-atom capable of efficiently converting linear polarization to its orthogonal state can achieve a controllable CP reflection phase via physical rotation. The proposed method focuses solely on optimizing the PT efficiency, transforming the conventional dual-objective optimization of reflection magnitude and phase into a single-objective problem, thereby significantly reducing the complexity of meta-atom design. Based on this concept, a wideband PT meta-atom is developed to achieve efficient polarization conversion by combining the radiated fields from a pair of complementary current modes: one generated by orthogonal electric currents, and the other produced by parallel electric currents and equivalent magnetic currents. The developed PT meta-atom is further employed to design a Ka-band CP RA with 16 × 16 meta-atoms for validation. It experimentally exhibits a 3-dB gain bandwidth of 38.6% spanning from 26.8 GHz to 39.6 GHz, a 3-dB axial ratio bandwidth exceeding 40%, and a maximum aperture efficiency of 40.1%, with an array profile of only 0.1λ₀ (where λ₀ is the free-space wavelength at the center frequency). This work provides an efficient and practical methodology for broadband CP wavefront control.