Ultrawide tunable terahertz phase shifter based on a double-layer liquid crystal–dielectric grating

Abstract

The ultrawide tunable terahertz (THz) phase shifter has always been in high demand by THz applications, especially in terms of broadband transmission and phase modulation. In this paper, we design and fabricate a composite device that combines a double-layer liquid crystal (LC) with a double-sided etched grating metasurface. By introducing the natural anisotropy of LC based on the artificial anisotropy of the metasurface, the anisotropy of the device is significantly enhanced, and this anisotropy can be dynamically modulated by an external field. When the LC molecules rotate in the x−y plane, the experimental results show that the phase difference can vary between −83∘ and 277° at 0.52 THz with a large phase-shift modulation depth of 360° (i.e., 2π). The same phase-shift modulation depth can be obtained when the LC molecules rotate in the x−z plane, in which the phase difference can vary between 207° and 567° at 1.14 THz. Our proposed composite device shows an ultrawide phase shift regulation and an ultra-large phase-shift modulation depth in the THz regime, which may provide a new strategy for various THz phase and polarization devices.