Numerical design of a high efficiency and ultra-broadband terahertz cross-polarization converter

A simple design of terahertz polarization converter has attracted great attention owing to the applicability of terahertz technology in broad fields such as imaging, non-destructive sensing, and communications, but remains a key challenge to simultaneously achieve both wide bandwidth and high conversion efficiency. Here we report a single-layer metasurface-based polarization converter formed by a combination of different resonator shapes that realizes cross-polarization conversion and achieves an ultra-broadband and high conversion efficiency with a wide oblique incidence in the terahertz region from 1.35 THz to 3.55 THz. The high performance and physical mechanism attributed to both electric and magnetic resonances of this proposed structure are guaranteed and analyzed by numerical study. Our design structure provides the frequency tunability to other frequency bands and possesses promising applications in terahertz polarization-control devices.