Development of a broadband reflectivity diagnostic for laser driven shock compression experiments.
A normal-incidence visible and near-infrared shock wave optical reflectivity diagnostic was constructed to investigate changes in the optical properties of materials under dynamic laser compression. Documenting wavelength- and time-dependent changes in the optical properties of laser-shock compressed samples has been difficult, primarily due to the small sample sizes and short time scales involved, but we succeeded in doing so by broadening a series of time delayed 800-nm pulses from an ultrafast Ti:sapphire laser to generate high-intensity broadband light at nanosecond time scales. This diagnostic was demonstrated over the wavelength range 450-1150 nm with up to 16 time displaced spectra during a single shock experiment. Simultaneous off-normal incidence velocity interferometry (velocity interferometer system for any reflector) characterized the sample under laser-compression and also provided an independent reflectivity measurement at 532 nm wavelength. The shock-driven semiconductor-to-metallic transition in germanium was documented by the way of reflectivity measurements with 0.5 ns time resolution and a wavelength resolution of 10 nm.
Department of Chemistry, University of California, Berkeley, California 94720, USA.
S J
SJ
Ali
Shock and Detonation Physics, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
C A
CA
Bolme
Lawrence Livermore National Laboratory, 7000 East Ave., Livermore, California 94550, USA.
G W
GW
Collins
Department of Earth and Planetary Science, University of California, Berkeley, California 94720, USA.
R
R
Jeanloz