Anisotropic All‐Optical Quantum Control of Polarized Terahertz Emission in Vertically Grown Graphene by Linearly Polarized Excitation

Polarized terahertz (THz) emission plays a pivotal role in applications such as polarization‐sensitive spectroscopy, sensing, and chiral phonon probing. Instead of relying on structural chirality in real space, an all‐optical route to polarization‐tunable THz emission from the momentum‐space carrier distribution in vertically grown graphene by linearly polarized light excitation is proposed. Anisotropic carrier distribution is induced by quantum interference (QI) mechanism between one‐ and two‐photon absorption pathways in momentum space under normal incidence. Unlike the photon drag effect, where the asymmetric carrier distribution is locked to the photon momentum, the QI‐induced injection photocurrent is optically controlled through the relative phase and polarization angle of the two‐color fields, enabling simultaneous control of the ellipticity and orientation of the emitted THz polarization ellipse. As such, we effectively distinguish the contributions of both photon drag and QI effects to THz wave generation under oblique‐incidence excitation. This study provides a new insight into the physical mechanism of polarization‐tunable THz emission and offers an experimental technique for polarized THz applications.