Ultrapure NIR-to-NIR single band emission of β-PbF2: Yb3+/Tm3+ in glass ceramics

Abstract

An ultrapure near infrared (NIR) emission entered at 800 nm upon 976 nm laser excitation (NIR-to-NIR) was observed in β-PbF2: Yb3+/Tm3+ glass ceramics (GCs). The ultrapure NIR-to-NIR single band emission originated from the 3H4 → 3H6 transition of Tm3+ with the ratio of NIR emission, and a blue band up to 9633 was obtained. Through detailed analysis of the crystal structure and the energy transfer between Tm3+ and Yb3+, it is elucidated that the host lattice with low phonon energy cooperative with the energy mismatch results in a dramatic population of the 3H4 state as well as ultrapure NIR-to-NIR single band emission. Moreover, up-conversion (UC) emission properties and the decay lifetimes of β-PbF2: Yb3+/Tm3+ in GCs were explored thoroughly. The results illustrate that efficient cross relaxation (CR) processes between Tm3+ generate the energy redistribution in UC emission spectra, further concentrating energy to NIR emission. These two issues can be treated as crucial factors on ultrapure NIR-to-NIR single band emission in β-PbF2: Yb3+/Tm3+ in GCs. The ultrapure NIR-to-NIR single band emission through 976 nm laser excitation is advantageous for enhancing resolution and has potential application in bio-imaging fields.