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

• Published in: Advanced optical materials 2019-10, Vol.7 (20), p.n/a
• Main Authors: Liang, Weizheng, Jiang, Yaohua, Guo, Jia, Li, Ning, Qiu, Wentao, Yang, Hao, Ji, Yanda, Luo, Sheng‐Nian
• Format: Article
• Language: English
• Subjects: interfacial thermal conductivity; Materials science; Metal-insulator transition; Mica; Modulation; Modulators; optical trigger threshold; Optics; Substrates; Switches; THz field modulation depth; THz modulators, THz switches; van der Waals heteroepitaxy; Vanadium oxides; VO2/mica films
• ISSN: 2195-1071; 2195-1071
• DOI: 10.1002/adom.201900647

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. Van der Waals (vdW) heteroepitaxial VO2/mica films are demonstrated with extremely low optical trigger threshold (0.21 mJ cm−2) and large THz field modulation depth (81.2%). The optical trigger threshold of VO2/mica films is only about 5% of that for VO2/Al2O3(101¯0) films, as a result of the vdW heteroepitaxy nature of VO2/mica films.