Growth and optical properties of ytterbium and rare earth ions codoped CaF2-SrF2 eutectic solid-solution (RE = Y3+, Gd3+, La3+)

Ytterbium and rare earth ions (RE = Y, Gd, La) codoped CaF2-SrF2 single crystals (3 at% Yb,6 at% RE:CaF2-SrF2) were fabricated by temperature gradient technology (TGT). All the space groups remain the same Fm3m as that of Yb:CaF2-SrF2. 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 Y3+ < Gd3+ < La3+. The segregation coefficients of Yb ions are 0.87 in Yb,La:CaF2-SrF2 and Yb,Gd:CaF2-SrF2, which are larger than 0.85 in Yb,Y:CaF2-SrF2 and 0.80 in Yb:CaF2-SrF2. Absorption spectra in the range of 200 and 400 nm were analysed with Yb2+ contents. The absorption and emission cross-sections in the range of 900-1100 nm were determined together with fluorescence lifetime. The saturation pump density I-sat, minimum pump density I-min and gain cross-section sigma(g) were analysed. Yb,La: CaF2-SrF2 has a relatively higher optical parameter (sigma(em) x tau, 0.52 x 10(-20) cm(2).ms), lower I-sat (3.68 kW/cm(2)) and I-min (0.50 kW/cm(2)) at 1038 nm indicating the potential application in high power laser. Low phonon energy of CaF2-SrF2 is 302 cm(-1) which is located between those of CaF2 and SrF2 as measured by Raman spectra. It is believed that ytterbium and rare earth ions (RE = Y3+, Gd3+, La3+) codoped CaF2-SrF2 eutectic solid-solution is promising for high-power and wavelength-tunable solid-state lasers. (C) 2020 Published by Elsevier B.V. on behalf of Chinese Society of Rare Earths.

Automated summary

Ytterbium and rare earth ions codoped CaF2-SrF2 single crystals were fabricated and their optical properties were analyzed, showing potential applications in high-power solid-state lasers. The study confirmed the effects of different rare earth ions on the crystal structure and optical performance.