High-Purity OAM Generator Using Low-Profile Huygens’ Metasurface With Stable Response

Orbital angular momentum (OAM) has garnered increasing interest in spectral multiplexing. In this letter, a low-profile, high-purity OAM transmitter array based on Huygens’ unit cell is proposed, and the adjustment of the non-resonant region is used to make it perform well at large oblique angles. Theoretical analysis and simulation verification demonstrate that the transmission coefficients of the proposed unit cell are greater than 0.8 at an oblique incidence range of 50°, and the phase change is approximately 20°. The unit cell's superior performance makes it suitable for low-profile applications, and we propose an OAM generator based on the unit cell to investigate the transmission performance with +2 OAM mode. Experimental results confirm that the Huygens’ metasurface successfully generates an OAM vortex beam under a small F/D ratio of 0.43. The OAM generator has achieved high purity from 9.3 GHz to 10.5 GHz, which is more excellent than 0.95 in simulation and 0.87 in measurement, respectively.