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

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