Subpicosecond Spectroscopic Ellipsometry of the Photoinduced Phase Transition in VO Thin Films.

We report the first application of broadband time-resolved pump-probe ellipsometry to study the ultrafast dynamics of the photoinduced insulator-to-metal transition (IMT) in vanadium dioxide (VO) thin films driven by 35 fs laser pulses. This novel technique enables the direct measurement of the time-resolved evolution of the complex pseudodielectric function of VO during the IMT. We have identified distinct thermal and nonthermal dynamics in the photoinduced IMT, which critically depends on the pump wavelength and fluence, while providing a detailed temporal and spectral phase map.

Adsorbate Isotherm Analysis by Reflection Anisotropy Spectroscopy on Copper (110) in Hydrochloric Acid.

Reflectance anisotropy spectroscopy (RAS) is a powerful optical probe that works on a polarization contrast basis. It can be operated in any environment, ranging from ultrahigh vacuum to vapor phases and liquids. The measured optical anisotropies are caused by several symmetry breaking effects and are exclusively assigned to the surface for otherwise bulk isotropic materials.