Interferometric detection of ultrafast thermoelastic transients in thin films:theory with supporting experiment

The thermoelastic generation and interferometric detection of ultrafast thermal and acoustic transients in a 300-nm-thick tungsten film are theoretically predicted and supported through experiment. Detection of these picosecond transients is obtained with a time-resolved spectroscopy scheme that uses a rotated cube, common path, self-stabilized Michelson interferometer and subpicosecond laser pulses from a mode-locked laser. These observations are theoretically described by the superposition of changes in the complex index of refraction and displacements over the absorption volume. Data analysis is completed in both time and frequency domains to support the validity of the classical assumptions involved in the theoretical derivation.