Infrared emission from calcium fluoride anion defects observed in synthetic material and natural fluorites

• Published in: Optical materials 2023-08, Vol.142, p.114012, Article 114012
• Main Authors: Moffatt, Jillian E., de Prinse, Thomas J., Tsiminis, Georgios, Klantsataya, Elizaveta, Payten, Thomas B., Teixeira, Lewis d.S., Smith, Barnaby W., Ottaway, David J., Spooner, Nigel A.
• Format: Article
• Language: English
• Subjects: Anion defect; Calcium fluoride; Fluorescence; Fluorine vacancy; Luminescence; Near-infrared
• ISSN: 0925-3467; 1873-1252
• DOI: 10.1016/j.optmat.2023.114012

Fluorine-based defect structures in calcium fluoride have previously been shown to emit visible-spectrum fluorescence when excited by UV light. This work shows the behaviour of a new fluorescence centre emitting in the near infrared at 1100–1200 nm when excited by visible light. This emission was most readily observed in natural fluorite samples, which have structural defects due to a long term exposure to environmental radiation, but was also induced in a synthetic calcium fluoride sample using intense UV light. Excitation of the near infrared emission reaches a maximum near the previously reported F-centre aggregate absorption peak. Emission is also “recharged” when excited by photons matching the fluorine interstitial migration energy. The measurement of this fluorescence could be used to monitor defects in optical grade fluorite caused by high power lasers and could also have applications in fluorite mineral detection during mining operations. Potential resetting of these optical defects is additionally discussed. •A new infrared luminescence emission was discovered in fluorite.•The luminescence is assigned to anion (F−) defects in the crystal structure.•The defect was induced in synthetic calcium fluoride using pulses of UV light.•The emission has potential applications in lens monitoring and fluorite detection.