NANOSECOND SCALE OPTICAL PULSE SEPARATIONS IN DOUBLE-EXPOSURE HOLOGRAPHIC-INTERFEROMETRY FOR INVESTIGATION OF TRANSIENT EVENTS

To investigate shock wave propagation in air, optical pulses with temporal separations ranging from 53 to 425 ns have been generated for use in double-exposure pulsed holography using a White cell [J. U. White, J. Opt. Soc. Am. 32, 285 (1942)] as an optical delay element. A single optical pulse from a Q-switched Nd:YAG laser was split using polarizing optics so that one pulse was guided directly to the experimental holographic recording setup; the other pulse was sent first into the White cell, emerging a set number of nanoseconds later. This delayed pulse then was used to record a second holographic exposure. Using the White cell construction, reproducible pulse separations between 53 and 425 ns could be generated. Shock wavefronts propagating at velocities greater than Mach 20 have been recorded using this method.