Advanced Spectroscopy Techniques for Probing Subsurface Chemistry in Heterogeneous Energetic Materials

Heterogeneous energetic materials typically consist of energetic molecular crystals in a polymer matrix with additional additives. This composite structure results in these materials being optically opaque, which means that standard optical spectroscopy techniques can only probe surface chemistry. However, there is a need to probe subsurface chemical reactions in order to better understand these materials’ detonation, deflagration, and aging chemistries. To address this diagnostic need we have been developing several novel optical techniques to perform subsurface spectroscopy including feedback assisted wavefront shaping, guidestar-guided digital optical phase conjugation (DOPC), self-healing laser beams, phase conjugation via degenerate four-wave mixing, and ultra-sound guided DOPC. In this talk we will provide an overview of all these techniques and discuss their prospects for performing subsurface spectroscopy during dynamic shock experiments. Additionally, we will discuss their applicability to characterizing aging heterogeneous energetic materials, which is of concern for aging weapons stockpiles.