Bochum 2015 – scientific programme
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K: Fachverband Kurzzeitphysik
K 3: Lasersysteme und deren Anwendungen I
K 3.4: Talk
Tuesday, March 3, 2015, 11:45–12:05, HZO 40
Laser-induced breakdown in an aluminum thin film and subsequent shock wave propagation in mini capillary — •Yun Kai1, Walter Garen1, Johannes Diekhoff1, and Ulrich Teubner1,2 — 1Institut für Laser und Optik, Hochschule Emden/Leer, Constantiaplatz 4, 26723 Emden — 2Institut für Physik, Carl von Ossietzky Universität Oldenburg, 26111, Oldenburg
A femtosecond-laser induces an optical breakdown in a thin aluminum film. As a consequence, an initially spherical shock wave is generated. The shock wave is coupled into a glass capillary (diameter of 0.75 mm or 0.5 mm, respectively). It is known that in free air, the initial shock wave will be decelerated to sound speed after propagating through a small distance of several millimeters. Due to the three dimensional propagation, the shock wave loses its kinetic energy quickly. In contrast to free air, the shock wave can propagate a much longer distance (several dozens of millimeters) in a capillary, which enables a quasi one dimensional propagation. Furthermore compared to breakdown in air, the breakdown in a solid state target (in the present study, Al films with a thickness in the range of 30-200 nanometers) can generate a much stronger shock wave. The shock wave velocities at different propagation distances are determined by a laser differential interferometer (LDI). The shock wave reflections and the boundary layer development inside the capillary are also investigated by the LDI and a schlieren setup.