Ultrafast dynamics of VO$_2$ thin films measured in pump-probe configuration

The semiconductor-metal transition of VO$_2$ continues to be a vigorously studied phenomenon due to complicated interplay between the structural change and the electronic bands. It is also potentially a very useful material, particularly because of its ultrafast transition to the metallic state excited with a femtosecond pulse. We have been exploring the effects of polarization of the pump in relation to the probe affects the sub-picosecond response of VO$_2$ thin films, which will be important in designing ultrafast switches. We have also been looking at pumping our VO$_2$ films with a THz source that directly pumps the lattice, and have found the film responds optically on a slower scale than when pumped with 800 nm, suggesting that there is an electronic response from disturbing the lattice.