Ultrafast vibrational spectroscopy imaging of nanoshock planar propagation

Variations of the velocity and pressure of repetitive 4 GPa laser-driven shock fronts in a polymer thin film are studied using spatially resolved ultrafast coherent anti-Stokes Raman Spectroscopy (CARS) measurements of shock compression of an anthracene optical gauge. Even though the radial profile of the laser pulse that generates the shock is a Gaussian that falls off steeply at the edges, optical saturation effects in the shock generation layer flatten out the shock front. Detailed measurements show the shock pressure, as indicated by the blueshift of an anthracene vibrational transition, and the shock velocity, as indicated by the arrival time at the anthracene gauge layer, remain constant within better than 5% over the central region probed by CARS, over a run distance of at least m. Received 30 July 2001 / Accepted 13 March 2002 Published online 17 June 2002