Multifunctional and tunable ultra-broadband linear to circle polarization converter based on VO 2 -integrated material

Considering that the metastructures (MSs) previously proposed usually perform in a single state, herein, a multifunctional and tunable ultra-broadband linear to circle (LTC) polarization converter based on phase transition material vanadium dioxide ( V O 2 ) is proposed in the terahertz (THz) region. By manipulating the temperature, the function of the LTC polarization conversion (PC) can be conveniently switched between transmission and reflection states. When the environment temperature is low, V O 2 presents the insulating state, and the MS can achieve ultra-wideband LTC PC from 0.57–0.83 THz with a relative bandwidth (RB) of 37.3%. When the temperature exceeds 68°C, LTC PC with the frequency bandwidth of 0.83–1.20 THz and 0.83–1.17 THz can be obtained in a reflection state when electromagnetic waves propagate forward and backward, whose RBs are 36.4% and 34.0%, respectively. Meanwhile, a broadband linear to linear (LTL) PC can also be realized in the range of 1.19–1.41 THz for the forward incident wave and 1.16–1.37 THz for the backward incident wave. The designed MS offers an effective method to realize four different functions and has tremendous potential value in realizing THz modulation devices, electromagnetic cloaking, and communication systems.