An ultra‐wideband linear‐to‐circular polarization converter in reflection mode at terahertz frequencies

Abstract A new approach to designing wideband wide‐angle ultrathin linear‐to‐circular (LTC) polarization converter is presented. The metasurface is composed of a symmetric hexagonal structure formed by parallel metal slits printed on a grounded dielectric substrate, which has a pair of independent mutually perpendicular u and v axes, along ±45° directions with respect to the y ‐axis direction. Numerical simulation results show that the LTC metasurface can convert a linear polarization incidence wave into a circular polarization reflected wave. The bandwidth of axis ratio less than 3 dB is 2.24 THz, which is from 2.37 THz to 4.61 THz, and the fractional bandwidth is 64% under normal incidence. Meanwhile, the unit cell of the LTC metasurface is low profile (0.35 λ 0 × 0.35 λ 0 × 0.118 λ 0 ) and compact. The polarization conversion efficiency can be maintained at over 85% at an angle of incidence up to 40°. Therefore, the proposed converter is useful for the development of the integrated THz polarization manipulation devices.