Optical transmission through inelastically deformed shocked sapphire: stress and crystal orientation effects

Plane shock wave experiments were performed to examine optical transmission in sapphire single crystals (c cut, a cut, and r cut) compressed to longitudinal stresses ranging between 119 and 260 kbar. Peak stress and particle velocity values in our experiments were obtained by compiling and analyzing published continuum data on shocked sapphire crystals. Time-resolved measurements, with nanosecond resolution, showed time-, stress-, and orientation-dependent changes in optical transmission beyond the Hugoniot elastic limit. Over the 300-680-nm range examined in our work, no wavelength dependence was observed. Loss of optical transmission in the stress range examined is due to inelastic deformation in shocked sapphire crystals. The present data reveal that inelastic deformation mechanisms are different in r-cut sapphire compared to a-cut and c-cut sapphire, and may be different for all three orientations examined. Although quantitative analysis of the time-dependent optical transmission data is not possible at present, optical transmission results have provided insight into inelastic deformation mechanisms in shocked sapphire. Present results are expected to be valuable for use of sapphire windows in shock wave experiments. (c) 2005 American Institute of Physics.