Complementary bilayer metasurfaces for enhanced terahertz wave amplitude and phase manipulation

Abstract

Manipulation of terahertz wave by metasurfaces has shown tremendous potential in developing compact and functional terahertz optical devices. Here, we propose complementary bilayer metasurfaces for enhanced te-rahertz wave amplitude and phase manipulation. The metasurfaces are composed of one layer of metal cut-wire arrays and one layer of their complementary aperture arrays separated by a dielectric spacer. Through the near-field coupling between transverse magnetic resonances in the metal apertures and electric resonances in the metal cut-wires, the structures can manipulate the cross polarization conversion and phase dispersion of terahertz wave. Particularly, the designed metasurfaces demonstrate a phase delay of 180° between two orthogonal axes with the same transmission amplitude between 0.70 and 1.0 THz, enabling a 45° broadband polarization conversion. When the metal cut-wires are rotated with respect to the apertures or the thickness of the dielectric spacer is changed, the amplitude and phase dispersion of the transmitted terahertz wave can be tuned. Such complementary coupled bilayer metasurfaces offer a new method to control the amplitude and phase dispersion of terahertz wave and promise great potential for applications in terahertz meta-devices.