Time-Resolved Surface Dynamics of Phase Transition Materials Visualized by Light Diffraction
Short flashes of laser light can be used to reversibly change the internal structure of the materials. Light pulses affect the electrons within the material, causing the material properties changed, and new states of matter can emerge. During the photoexcitation process the electronic and structural properties change at the same time, making important study this effect in time domain. Time- and angle-resolved hemispherical elastic light scattering (tr-ARHELS) provides unique opportunity to investigate light-induced phase transition phenomena in phase-change correlated oxides. Using angle-resolved light scattering technique one can obtain statistical information about surface irregularities of different sizes, which is useful to detect functional defect and to understand the nature of surface imperfections. To monitor insulator-to-metal phase transitions in vanadium oxides, a transient imaging of coherent optical diffraction was performed by using tr-ARHELS setup, where 3D scattering indicatrix was visualized with femtosecond resolution. To obtain information on correlation of surface irregularities, we developed new algorithm to compute surface autocorrelation function (ACF) from 3D scattering indicatrix. These algorithms produce a robust and precise reconstruction of the ACF and PSD pair. A real-time reconstruction of ACF was achieved for femtosecond spectroscopy of phase-change materials.
This material is based upon work supported by the U. S. Army Research Laboratory and the U. S. Army Research Office under contract# W911NF-15-1-0448, and by NSF Grant# DMR-1531627.