Reflective ultra-wideband dual-band linear-to-circular polarization converter based on metasurface

A dual-frequency ultra-wideband line-to-circular polarization converter based on metasurfaces is proposed in this paper. The metasurface is composed of a symmetrical semicircular structure connected to a rectangular metal strip with a deflection direction at a 45° angle to the y-axis, and its dielectric substrate layer is fabricated on the metal layer. When y-polarized waves are incident, the polarization converter can convert linearly polarized incident waves into circularly polarized reflected waves. The frequency range with an axial ratio less than 3 dB is 14.0–20.1 THz and 23.5–37.4 THz, respectively. The obtained bandwidth is 6.1 THz and 13.9 THz, which generates left-handed circularly polarized waves (LCP) and right-handed circularly polarized waves (RCP). The linear circular polarization converter unit is compact and easy integration. When the oblique incidence angle is 40°, the minimum elliptical polarization conversion rate within the working axis ratio 3 dB bandwidth is above 80%. When the polarization angle is 20°, the elliptical polarization in the operating frequency band is also above 78%. As the reflective polarization converter has such excellent characteristics, which make it having high research value for electromagnetic devices in the terahertz frequency band.