Terahertz wave manipulation and detection based on liquid crystals

Liquid crystals (LCs) have very attractive properties that the response can be controlled by the external stimulus such as electric field and temperature. Terahertz (THz) devices based on LC have wide applications. But the development of high-performance LC THz functional devices is still in its infancy. We firstly develop a large birefringence LC material in THz range. Then broadband tunable transmissive driven with porous graphene and reflective THz waveplates based on this LC are proposed. Furthermore, graphene-assisted high efficiency tunable THz metamaterial absorber is demonstrated. A magnetically and electrically polarization-tunable THz emitter that integrates a ferromagnetic heterostructure and the large-birefringence LC is also demonstrated. Last but not least, we use a temperature-supersensitive cholesteric liquid crystal (CLC) to not only measure the beam profiles but also detect the powers of THz waves generated from a nonlinear crystal pumped by a table-top laser, which is visible, cost-effective, portable and robust at room temperature. These LC based THz devices can be used in applications such as THz imaging, biological sensing, and inspection.