Dual-band transmissive circular polarization generator with high angular stability.

Metasurfaces (MSs) offer us an efficient way to control electromagnetic wave polarization due to its capability of flexible wave manipulation and compact configurations. However, the design of dual-band polarization conversion MS with high angular stability is still a challenge, especially in transmission geometry. Here, we propose a dual-band linear-to-circular (LTC) polarization conversion MS with high angular stability by using an array of multi-resonance meta-atoms. The meta-atom consists of two outer double split-ring layers and a central bar layer with circle-slot and can realize circular polarization at two bands with high efficiency and angular stability. The MS can transform the x-polarized wave into right-hand circular polarization (RHCP) at lower band and left-hand circular polarization (LHCP) at higher band and an opposite role for the y-polarized wave. The results show that the MS operates with insertion loss less than 0.5 dB and 0.3 dB and axial ratio below 3 dB in the frequency range of 9.05-9.65 GHz and 12.55-13.1 GHz, respectively. Moreover, our MS is insensitive to the oblique incident waves and can operate at high performance with the incident angle less than 55°. The proposed MS provides a new avenue to design meta-devices with dual frequency property and also high angular stability.