ULTRAFAST MICROSCOPY OF SHOCK-WAVES USING A SHOCK TARGET ARRAY WITH AN OPTICAL NANOGAUGE

A large area shock target array was fabricated. By moving the array th rough a ps pulsed laser beam, shock waves could be reproducibly genera ted at a high repetition rate of up to ten shocks per second. The dyna mics of shock wave propagation through various layers of the array wer e studied using optical nanogauges. A nanogauge is a sub micron thick layer whose optical properties are affected when the shock front passe s through the layer. Since shock velocities are typically a few nm/ps, nanogauges can be used to study picosecond time scale shock dynamics. Using picosecond optical microscopy on targets with different thickne ss aluminum layers, it was found that the shock required 0.5 ns to for m and then it propagated for a few ns with a constant velocity of 8.3 km/s (8.3 nm/ps), indicating a shock pressure of 49 GPa. The arrival t ime jitter of many hundreds of shocks, at an aluminum/polymer interfac e was found to be +/-50 ps. The shock propagation through a polymer, p olyester, was studied by observing the arrival of the front at a 50 nm thick nanogauge embedded in the polymer. When the shock was transmitt ed from the aluminum to a polymer layer, its velocity was 5.5 km/s, in dicating a shock pressure of 14 GPa, in good agreement with shock impe dance calculations. The shock target array is a flexible method of stu dying picosecond time scale dynamics of materials at and just behind t he shock front. The use of different optical nanogauges, such as dye-d oped polymer films, which can sense the temperature, pressure, and whi ch indicate multiphonon up pumping, is briefly discussed.