Growth and optical properties of ytterbium and rare earth ions codoped CaF2-SrF2 eutectic solid-solution(RE=Y^(3+),Gd^(3+),La^(3+))

Ytterbium and rare earth ions(RE=Y,Gd,La)codoped CaF_(2)-SrF_(2)single crystals(3 at%Yb,6 at%RE:CaF_(2)-SrF_(2))were fabricated by temperature gradient technology(TGT).All the space groups remain the same Fm3m as that of Yb:CaF_(2)-SrF_(2).The lattice parameter a,unit cell volume V,as well as bond length of Ca/Sr-F and F-F increase in the sequence of rare-earth ions radius Y^(3+)<Gd^(3+)<La^(3+).The segregation coefficients of Yb ions are 0.87 in Yb,La:CaF_(2)-SrF_(2)and Yb,Gd:CaF_(2)-SrF_(2),which are larger than 0.85 in Yb,Y:CaF_(2)-SrF_(2)and 0.80 in Yb:CaF_(2)-SrF_(2).Absorption spectra in the range of 200 and 400 nm were analysed with Yb^(2+)contents.The absorption and emission cross-sections in the range of 900-1100 nm were determined together with fluorescence lifetime.The saturation pump density/Sat,minimum pump density/m in and gain cross-section were analysed.Yb,La:CaF_(2)-SrF_(2)has a relatively higher optical parameter(δem×t,0.52×10^(20)cm^(2)·ms),lower Isat(3.68 kW/cm^(2))and^min(0.50 kW/cm^(2))at 1038 nm indicating the potential application in high power laser.Low phonon energy of CaF_(2)-SrF_(2)is 302 cm^(-1)which is located between those of CaF_(2)and SrF_(2)as measured by Raman spectra.It is believed that ytterbium and rare earth ions(RE=Y^(3+),Cd^(3+),La^(3+))codoped CaF_(2)-SrF_(2)eutectic solid-solution is promising for high-power and wavelength-tunable solid-state lasers.