Color Selective Control of Terahertz Radiation Using Two-Dimensional Hybrid Organic Inorganic Lead-Trihalide Perovskites*

Controlling and modulating terahertz signals is of fundamental importance to allow systems level applications. We demonstrate an innovative approach for controlling the propagation properties of terahertz (THz) radiation, through use of both the excitation optical wavelength and intensity. We accomplish this using two-dimensional (2D) layered hybrid trihalide perovskites that are deposited onto silicon substrates. Optical absorption in 2D perovskites occurs over a broad spectral range above the bandgap, resulting in free carrier generation, as well as over a narrow spectral range near the band-edge due to exciton formation. We find that only the latter contribution gives rise to photoinduced THz absorption. By patterning multiple 2D perovskites with different optical absorption properties onto a single device, we demonstrate both color selective modulation and focusing of THz radiation. These findings open new directions for creating active THz devices.