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In this article, we present a dual‐band linear‐to‐circular transparent converter by bi‐layered chiral metamaterial (CMM) with an inverted “G” array in microwave region. The proposed metasurface consists of three layers which are the upper layer of the metasurface with a periodic regular metallic inverted “G” and wire array, the dielectric layer, and the bottom layer operating as chiral symmetric structure of the upper. The simulation results show that the transmitted right‐circular polarized wave with the axial ratio of 3 dB or less is in the range of 8.6‐10.9 GHz and the left‐circular polarized wave is within 18.1‐22.5 GHz when y‐polarized forward wave is normally incident. Specifically, the polarization conversion transmission can be maintained at over 85% at angle of incidence up to 40°. Therefore, the proposed CMM device is useful for the development of the integrated polarization manipulation devices.

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 AE45 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 (0.35λ 0 × 0.35λ 0 × 0.118λ 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. K E Y W O R D S broadband metamaterial, linear-to-circular converter, polarization converter

Multiband linear‐to‐circular (LTC) metamaterial converters have promising applications in modern optical system. However, it is challenging to design a converter with conversion bands of more than four and the axial ratio of less than 3 dB due to the coupling interaction of different resonant structures in a unit cell. In this article, we demonstrate a broad class of self‐complementary THz infinite thin metasurfaces composed of supercells of fractal metal rectangular patches and holes dimers of spanning 1 THz octave in bandwidth, while still being highly efficient. The advantages of this converter are as follows. The device is theoretically nonthickness; the LTC polarization conversion can be achieved in both the reflected and transmitted fields; the phase difference between two orthogonal linear polarization components is theoretically 90° in any frequency. Therefore, an eight‐band LTC converter is achieved in reflection and transmission modes. This new nonthickness multiband device will demonstrate a major advance toward an LTC synthetic metasurface in the THz band.