Broadband and wide angle quarter-wave plate based on single-layered anisotropic terahertz metasurface

Abstract Broadband control of polarization state is essential for terahertz applications ranging from non-destructive testing to imaging in medicine and wireless communications. We present a single-layered terahertz anisotropic metasurface quarter-wave plate consisting of hybrid metallic wire grating arrays, which enables broadband linear to pure circular polarization conversion with an ellipticity over 0.99 and 43% bandwidth of the central wavelength. The broadband effect is robust across a wide range of incident angles. Interestingly, angle-tunable arbitrary polarization states are implemented by changing the angle of incidence at other frequencies. Such single-layered broadband quarter-wave plate provides a route to develop broadband polarization conversion components, facilitating compact applications of terahertz technologies.