Measurement of transit time for femtosecond-laser-driven shock wave through aluminium films by ultrafast microscopy

Shock waves in unconfined aluminium films of varying thicknesses from 3 to 10 μm induced by a single fs-laser-pulse with a full width half maximum width of about 130 fs at λ = 800 nm wavelength have been investigated by using ultrafast microscopy. With successive sub-picosecond-resolved micrographs of the aluminium/α-quartz interface taken at various probing times, the shock transit time in aluminium films of different thicknesses was measured accurately. From the best linear fit of the transit time versus the thickness of aluminium films, the shock velocity was measured to be 9.0 ± 0.4 km s-1 at the laser intensity of 7.84 x 1013 W cm-2. From the shock velocity D the shock pressure P and temperature T were calculated to be 69 ± 5 GPa and 1852 ± 400 K, respectively. Experimental results in good agreement with previous theoretical and experimental works indicate that the time-resolved ultrafast microscopy technique is a fairly accurate and feasible technique for studying fs-laser-driven shock waves in opaque thin films.