Seminars

Abstract: Digital holography is a powerful tool for quantitative, three-dimensional imaging. It has been successfully applied to estimate the size, morphology, three-dimensional (3D) position, and 3D velocity of particles, fragments, and droplets in a variety of multiphase flows. In explosive, supersonic, and hypersonic environments, however, shock-waves and density gradients impart severe phase distortions that obscure objects in the field-of-view, making it difficult to make quantitative estimates. In this talk, several newly-developed digital holography techniques capable of cancelling phase distortions from shock-waves and thermal gradients will be discussed. First, we introduce phase conjugate digital in-line holography (PCDIH), which utilizes nonlinear optical four-wave mixing to create a phase conjugate beam capable of cancelling phase distortions in-camera. This technique is used to capture video at up to 5 million-frames-per-second (5 MHz) using a pulse-burst laser and ultra-high-speed cameras. Next, we discuss a recalculated intensity propagation phase holography (RIPPH) technique, which captures the entire electric field hologram to enable numerical cancellation of phase distortions. We demonstrate how both of these techniques can be used to remove distortions and drastically improve quantitative estimates. Finally, we apply these methods to image through laser-spark generated shock-waves, study clouds of combusting metal particles, and track explosively generated hypersonic fragments. Complementary techniques for measuring particle temperatures and gas properties will also be discussed.

Bio: Ellen Mazumdar started at the Woodruff School of Mechanical Engineering at Georgia Tech in 2019 and has a courtesy appointment with the Guggenheim School of Aerospace Engineering. She graduated with her B.S., M.S., and Ph.D. from Massachusetts Institute of Technology (MIT) and was the recipient of the DoD NDSEG and NSF GRFP Fellowships.  Dr. Mazumdar completed a postdoctoral appointment in the Diagnostic Science and Engineering group at Sandia National Laboratories in Albuquerque, New Mexico. Her work was the recipient of the Marshall Award for Best Paper at ILASS Americas. At Georgia Tech, she currently leads the Sensing Technologies Laboratory, which focuses on developing new techniques for studying energetic materials, combustion phenomena, hypersonics, and multiphase flows.  Her group utilizes new optical diagnostics, magnetostatic methods, composite sensing materials, and system identification techniques to study these complex physical phenomena.