A flexible U-shaped metamaterial terahertz quarter-wave plate with corner design.

• This paper aims to break through the bottleneck problem that the right-angle can'tbe perfectly machined in the existing photolithography process because of the light diffraction. The tangent treatment of U-shaped corners is carried out in this paper, thus fundamentally reducing the requirement for photolithography process accuracy from the beginning of design. • The equivalent dielectric parameter of substrate can be determined by comparing the experimental data of QWP transmission characteristics with the simulation data obtained by scanning the dielectric parameters under the same design. The proposed equivalent dielectric parameter of the substrate can provide the correct dielectric parameter input for accurate simulation of subsequent designs. • This paper gives a new empirical formula for our multilayer U-shaped metamaterial to help understand the effects of unit cell size, corner tangent size, and equivalent dielectric parameter of substrate on QWP transmission characteristics in the simulation. To overcome the bottleneck problem that the right-angle of metamaterial metal unit cell can't be perfectly machined in the existing photolithography process, the tangent treatment of U-shaped corners is carried out in this paper. Using two layers of U-shaped metamaterial gold unit cell with corner design sandwiched with three polyimide layers, a flexible terahertz quarter-wave plate (QWP) with polarization conversion efficiency of 0.8 and operating bandwidth of 0.2 THz is obtained. The equivalent dielectric parameter of substrate is proposed to provide the correct dielectric parameter input of polyimide for the precise simulation. The influences of the equivalent dielectric parameter, the corner tangent length and the geometric parameters of the metamaterial metal unit cell on the QWP performance are analyzed. To better understand the effects of these parameters on the QWP performance, an empirical formula for multilayer U-shaped metamaterial is given in this paper. This work has good application potential in terahertz wireless communications, terahertz imaging, and terahertz medical diagnostic systems and other fields. [ABSTRACT FROM AUTHOR]