Recent progresses in terahertz modulators based on metal halide perovskites

Rapid development of terahertz technology promotes a series of terahertz functional devices that emerged, such as source, modulator, filter, and detector. Among the ones, high-performance terahertz modulators are desperately needed due to they serve as the basis for real-world terahertz technology applications. Compared with conventional semiconductor materials, perovskite materials have been demonstrated to have noticeably improved photoelectric characteristics. In this case, the incorporation of perovskite materials into terahertz modulation is critical because it may open up new avenues for improving the performance of terahertz modulators. Therefore, the study of perovskite-based terahertz modulators has attracted considerable attention from scientific researchers and engineers. In this review, the fundamental properties and fabrication techniques of three-dimensional (3D) and two-dimensional (2D) perovskite materials are first introduced. Next, the theory and mechanism of terahertz modulation by optical and electrical excitations are outlined together with crucial performance evaluating parameters. Then, we concentrate on the recent progress in perovskite-based terahertz modulators according to various device structures and optimization techniques. Finally, the challenges and opportunities of the perovskite-based terahertz modulators are discussed as well as prospects.