“Taggants” is a category name for materials that do not occur naturally in the tagged substrate, ink, or other carrier. Rare Earth taggants can be detected using IR wavelengths that cause an anti-stokes reaction that is not common in nature, which results in the emission of a higher energy (in the visible spectrum) than the excitation source (IR). Other materials in this broad category include DNA and stable isotopes that require lab tests to verify their presence, at very low (parts per billion) concentrations. Utilized as a secondary forensic feature.

Taggants responding to 980nm excitation