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.

本文提出了一种基于超表面的双频超宽带线圆偏振转换器。该超表面由对称的半圆形结构连接到偏转方向与y轴成45°角的矩形金属条组成，其介电基板层制作在金属层上。当y偏振波入射时，偏振转换器可以将线偏振入射波转换为圆偏振反射波。轴比小于3 dB的频率范围分别为14.0-20.1 THz和23.5-37.4 THz。获得的带宽为6.1 THz和13.9 THz，产生左旋圆极化波（LCP）和右旋圆极化波（RCP）。线性圆偏振转换器单元结构紧凑且易于集成。当斜入射角为40°时，工作轴比3 dB带宽内的最小椭圆偏振转换率在80%以上。当偏振角为20°时，工作频段的椭圆偏振率也在78%以上。由于反射式偏振转换器具有如此优异的特性，使得其对于太赫兹频段的电磁器件具有很高的研究价值。