Picosecond strain waves in PTV

We studied the propagation of thermo-optically excited transient strain waves in thin films of PTV by means of the ps time-resolved pump-probe technique. We find that ultrasound at high frequencies (above 10GHz) does not properly propagate through the polymer film. Since ultrasound damping is frequency-Independent in the time interval of up to 3ns, we speculate that disorder-induced localization may be responsible for the high frequency cut-off.