Luminescence Property and Judd-Ofelt Analysis of 0.6%Pr, x%La:CaF₂ Crystals

Calcium fluoride (CaF2) is an attractive laser material due to its broad transmission range (0.125-10 mu m), good thermal conductivity (9.71 W/(m center dot K)) and low coefficient of nonlinear effect. In Pr:CaF2 crystal, the [Pr3+-Pr3+] cluster lead to fluorescence quenching at lower concentrations of Pr3+ ions. Therefore, co-doping of La ions in CaF2 to break the [Pr3+-Pr3+] cluster deserves further exploration. In this work, a series of Pr:CaF2 single crystals co-doped with different concertation of La3+ ions were successfully grown by temperature gradient technique (TGT). The X-ray powder diffraction, absorption spectra, fluorescence spectra and fluorescence decay lifetime of Pr,La:CaF2 crystals were measured. Obtained data demonstrated that the Pr:CaF2 crystals still had the cubic crystal structure after co-doped with La3+ ions. The largest stimulated emission cross-sections of P-3(0)-> H-3(6) (604 nm) and P-3(0)-> F-3(2) (640 nm) transitions were calculated to be 1.36x10(-20) cm(2) and 3.18x10(-20) cm(2) with FWHM of 17.0 nm and 3.8 nm, respectively. With the increase of La3+ ion concentration, the value of FWHM increased from 15.84 nm to 18.53 nm of P-3(0)-> H-3(6). The largest fluorescent lifetime and spectral quality factor of 0.6%Pr, 10%La:CaF2 ( atom fraction) is 45.82 mu s and 1.458x10-18 cm(2)center dot mu s, respectively. All above results show that the [Pr3+-Pr3+] ions quench clusters are broken by La3+ ions. The Pr, La: CaF2 crystal is a potential laser gain material for orange-red laser operation.