Two‐Color Coherent Control of Chiral Terahertz Emission in Halide Perovskites

ABSTRACT Dynamic polarization control of terahertz (THz) wave is crucial for advancing applications in 6G communications, molecular sensing and spectroscopic analysis. However, current solid‐state THz emitters are limited by restricted polarization tunability, particularly in achieving dynamic control over ellipticity and handedness. Herein, we demonstrate that halide perovskite (MAPbI 3 ) thin film provide an efficient platform for polarization‐controlled THz emission under two‐color ( ω + 2 ω ) excitation. The MAPbI 3 film exhibits exceptional THz emission efficiency under this excitation scheme, outperforming both conventional and 2D semiconductors. The THz emission is dominated by ultrafast injection photocurrents, which are coherently modulated by the relative phase and polarization angle between ω and 2 ω beam. Notably, by tuning the polarization angle, both left‐ and right‐handed chiral THz waves can be generated with continuously tunable ellipticity and orientation. This high degree of tunability arises from the fourth‐rank tensor of the third‐order nonlinear conductivity, which determines both the amplitude and direction of the coherent injection photocurrent. These findings establish halide perovskites as a versatile solid‐state platform for coherent control generation of chiral THz radiation, opening new avenues for polarization‐sensitive THz photonic technologies.