Photoinduced Metal-Like Phase of VO<sub>2</sub> with Subns Recovery
J. Kenji Clark, Ya‐Lun Ho, Hiroaki Matsui, Bertrand Vilquin, Hitoshi Tabata, Jean‐Jacques Delaunay
Abstract
Vanadium dioxide is a unique insulator–metal transition material with a near room temperature transition temperature that is a major focus of interest in burgeoning fields such as all-optical devices and neuromorphic computing. The photoinduced insulator–metal transition of VO2 is of particular interest for the development of ultrafast optical devices; however, the recovery dynamics of VO2 after a photoinduced insulator–metal transition must be better understood. Here, the time-resolved differential transmittance of VO2 after excitation by an ultrashort pump laser pulse and the recovery of VO2 back to its equilibrium state are studied. For pump laser fluences in a midfluence region, which is found to match the midfluence region for the recently discovered photoinduced monoclinic metal phase of VO2, a strong nonlinear change in the differential transmittance of VO2 with fast recovery is discovered. In the midfluence region, a 15 nm VO2 thin film is shown to have a differential transmittance at the saturation value of 14%, while exhibiting full recovery in less than 600 ps. These results demonstrate that the large changes in the optical properties of VO2 associated with its photoinduced insulator–metal transition can recover on subns time scales, allowing for efficient GHz speed all-optical and neuromorphic computing devices using VO2.