Electrically active control of terahertz waves in a hybrid metasurface–grating structure with a liquid crystal

A reflective terahertz phase shifter for wide-range dynamic and continuous phase modulation is proposed. By injecting a tunable liquid crystal between the slotted metasurface and the grating microstructure, the phases of reflected waves can be modulated with different electrically driven methods. Numerical simulations show that the proposed terahertz phase shifter has a phase difference of more than 360° between unbiased and biased states. Furthermore, an array of 35×35 patch elements was designed and fabricated. The performance of the phase shifter provides more than 360° between 379.6 and 391.8 GHz, where the maximum phase shift reaches 422.4° at 385.9 GHz. Moreover, the fully electrically controlled phase modulation of more than 180° is achieved between 382.0 and 394.1 GHz, with a maximum phase modulation of 248.4° at 383.3 GHz. This work may provide a reflective terahertz phase modulator for beam steering.