Technique for Measuring Transmittance of Optical Windows under Dynamic Loading and Its Application

A measurement technique for optical transmittance of window material under gas-gun-driven shock loading condition was developed, in which a pulsed light source of semiconductor laser was mounted in the projectile and along its central axis to measure the transmittance change of transparent sample during loading and unloading processes. The advantages of the light source over the traditional xenon-lamp are: (1) the work voltage is only 4.5 V; (2) the response time is less than 500 ns; (3) the output power is stable. The improved method provides an important tool for studying the transparency change, absorption, and failure of brittle materials. Quartz glass, as an example, is found to partially lose its transparency during the unloading process after shock compression of 1.8 GPa, and the decrease of transmittance is as high as 30%. The results do not support the explanation of liquid-solid phase transition given by literature.