The polarizing light microscope (PLM) can be used to characterize the optical properties of numerous materials. The image at right depicts conoscopic (top and leftmost image) and orthorscopic (bottom most images) observations associated with a single crystal of the highly explosive material known as TATP, or triacetone triperoxide. In the last several years, this explosive has been implicated in terrorist activities, making its characterization and identification of paramount importance to first responders. (Note: this figure illustrates how immersion methods and polarized light microscopy can be used to determine the refractive indices associated with a biaxial material).
Ref: This research was carried out while working at the McCrone Research Institute (Chicago, Ilinois), and in collaboration with Jack Hietpas, formerly of Microtrace (Elgin, Illinois) and currently at Syracuse University.