https://www.thermofisher.com/blog/mining/is-it-natural-or-man-made-detecting-treated-gemstones-with-ft-ir-spectroscopy/
FT-IR spectroscopy can confirm that rubies and sapphires are corundum and not a simulant or gemstone imposter in the mining industry,
man madenaturaltreatedgemstonesft
https://www.southampton.ac.uk/research/projects/advanced-characterisation-of-mid-ir-hollow-core-fibres-for-applications-in-gas
Advanced Characterisation of Mid-IR Hollow Core Fibres for Applications in Gas Spectroscopy and High Power Beam Delivery.
advancedcharacterisationmidirhollow