ErF microcrystals controllably deposited in perfluoride glass for upconversion red emission.

To the best of our knowledge, this paper first reports ErF microcrystals controllably deposited in perfluoride glass using phase-separation engineering techniques. The sample exhibited strong upconversion red-light emission owing to the small distance between Er ions and low phonon energy (585 cm). The sample has a high red/green ratio of up to 18.