Van der Waals Heteroepitaxial VO₂/Mica Films with Extremely Low Optical Trigger Threshold and Large THz Field Modulation Depth

Abstract Materials with low optical trigger threshold and large THz field modulation depth are highly desirable for THz switches and modulators. VO₂, a classical strongly correlated oxide undergoing a sharp metal–insulator transition (MIT), is advantageous for its large THz field modulation depth by virtue of MIT. However, for optically triggered VO₂‐based THz switches and modulators, high pump laser intensity is normally required to trigger the MIT, adding considerable costs to THz systems. Reducing optical trigger threshold of VO₂ is of substantial interest in the THz science. Here, van der Waals (vdW) heteroepitaxial VO₂/mica films are reported with extremely low optical trigger threshold and large THz field modulation depth. Such VO₂ films can be used to fabricate low cost but high performance THz switches and modulators. The vdW‐bonded VO₂ film–substrate interface allows for negligible disturbance to the VO₂ lattice by the mica substrate and reduces thermal conduction to the substrate, boosting the MIT and thus, reducing the pump threshold.