Publications Details

Ultra-high-speed pulse-burst phase conjugate digital in-line holography for imaging through shock-wave distortions

Mazumdar, Yi C.; Heyborne, Jeffery D.; Guildenbecher, Daniel R.; Smyser, Michael E.; Slipchenko, Mikhail N.

Digital in-line holography techniques for coherent imaging are important for object sizing and tracking applications in multiphase flows and combustion systems. In explosive, supersonic, or hypersonic environments, however, gas-phase shocks impart phase distortions that obscure objects. In this work, we implement phase-conjugate digital in-line holography (PCDIH) with both a picosecond laser and a nanosecond pulse-burst laser for reducing the phase distortions caused by shock-waves. The technique operates by first passing a forward beam of coherent light through the shock-wave phase-distortion. The light then enters a phase-conjugate mirror, created via a degenerate four-wave-mixing process, to produce a return beam with the opposite phase-delay as the forward beam. By passing the return beam back through the phase-distortion, phase delays are canceled producing phase-distortion-free images. This technique enables the measurement of the three-dimensional position and velocity of objects through shock-wave distortions at rates up to 500 kHz. This method is demonstrated in a variety of experiments including imaging supersonic shock-waves, sizing objects through laser-spark plasma-generated shock-waves, and tracking explosively-generated hypersonic fragments.