Ali S J, Bolme C A, Collins G W, Jeanloz R
Department of Chemistry, University of California, Berkeley, California 94720, USA.
Shock and Detonation Physics, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
Rev Sci Instrum. 2015 Apr;86(4):043112. doi: 10.1063/1.4917195.
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.
构建了一种垂直入射的可见光和近红外冲击波光学反射率诊断装置，以研究材料在动态激光压缩下光学性质的变化。记录激光冲击压缩样品光学性质随波长和时间的变化一直很困难，主要是因为涉及的样品尺寸小且时间尺度短，但我们通过展宽超快钛宝石激光器产生的一系列延迟800纳米脉冲，在纳秒时间尺度上产生高强度宽带光，成功做到了这一点。在单次冲击实验中，该诊断装置在450-1150纳米波长范围内进行了演示，最多可获得16个时间位移光谱。同时，离轴垂直入射速度干涉测量法（任意反射镜速度干涉仪系统）对激光压缩下的样品进行了表征，并在532纳米波长处提供了独立的反射率测量。通过具有0.5纳秒时间分辨率和10纳米波长分辨率的反射率测量，记录了锗中冲击驱动的半导体到金属的转变。
