Rapid terahertz wave manipulation in a liquid-crystal-integrated metasurface structure

Abstract

A terahertz phase shifter based on liquid-crystal-integrated metasurface is proposed, which contains a three-slotted array structure and comb grating. The orientation of the liquid crystal molecules can be completely controlled by the direction of the electric field. From the acquired experimental results, it was demonstrated that the phase shift exceeds 300° in the range of 378.6 - 390.8 GHz, whereas the maximum phase shift reaches 374.1° at 383.1 GHz. The molecular reorientation transient process induced by the external electric field in the liquid crystal was measured and analyzed. Based on the molecular reorientation mechanism, which can be divided into three processes, a rapid modulation mechanism was demonstrated. From the performance of the proposed device, an actively controllable phase delay and reflectance with a cycle switching time of approximately 0.3 s was achieved, which is remarkably faster than the usual cycle time that exceeds 8 s. Our work provides useful ideas for improving the response speed of LC-based terahertz devices, which is considered of great significance for several applications, in terms of terahertz reconfigurable devices.

Novel switching of liquid crystals for use in rapid THz phase shifters discovered from the dimensional effects of electrodes

“…Although TIP-TOP switching improves some device characteristics, the details of its operation, such as how the electric fields are distributed and how the LCs respond to the fields, are not necessarily understood. A more recent study 16 also demonstrated that applying an electric field to each switching process can effectively overcome the extremely slow response of LC-based THz switching.…”

The Birefringence and Extinction Coefficient of Ferroelectric Liquid Crystals in the Terahertz Range

“…Liquid crystal (LC) is a substance composed of rod-like molecules with particular directions [25], and these molecules can modulate and regulate optical field [26,27], especially in the THz domain due to its high birefringence in the THz region [28]. Thus, LC is a suitable material for tunable photonic devices working in the THz environment, such as a voltage-controlled THz phase shifter and quarter-wave plate [29][30][31][32][33]. Recently, plasmon-induced LC metamaterial was implemented to fabricate an electrically tunable THz modulator with a large modulation depth and low insertion loss [34].…”