Triplet cooperative luminescence of Yb3+-doped AF2 (A=Ca, Sr) crystals

The triplet cooperative luminescence (TCL) of Yb3+- doped AF2 (A=Ca, Sr) was studied under excitation of near infrared (NIR) light. First, the TCL from Yb3+ ions in the SrF2: Yb3+ was studied for the first time under NIR excitation. Next, the TCL and dimer cooperative luminescence (DCL) intensities in the CaF2 and SrF2 are compared at room temperature. Finally, we discuss why the cooperative luminescence intensities of CaF2: 1%Yb3+ in the ultraviolet (UV) and visible region is much stronger than the SrF2: 1%Yb3+.