Extend the Bandwidth of Terahertz Polarization Convertors Further via All-Dielectric Grating Structures

The emergence and rapid development of metamaterials have provided crucial technological support for terahertz polarization conversion devices. However, the current efficiency and bandwidth of terahertz metamaterial polarization convertors are generally deficient due to limitations in material types or design mechanisms. Here, we propose a new approach for designing the geometric parameters of subwavelength grating structures based on the equivalent medium theory. By introducing a characteristic ration
α
, we enhance design flexibility and further improve the effective bandwidth by utilizing materials with higher refractive indices. The estimated optimal effective bandwidth for quarter-wave pate can reach up to ∼7.42 THz. Furthermore, this endeavor presents a good approach towards achieving ultra-wideband conversion of arbitrary polarization states at terahertz frequencies. The designed metasurface provides a new perspective on polarization manipulation of terahertz waves, which holds immense potential for diverse applications in terahertz systems.