关键词: 氟化钙晶体, 温度梯度法, 晶体生长, 多孔坩埚, 激光晶体, 光谱性能

Abstract: CaF₂ and Sr_xCa_1-xF₂crystals with different doping concentration of Ho³⁺ and Y³⁺ were successfully grown by the temperature gradient technique (TGT) in self-designed furnace, which can realize the synchronous growth of seven crystals with different doping concentration. The size of the grown crystals is about ϕ15 mm×55 mm, and the growth cycle is about 6 d. The spectral properties of 4%(atomic fraction)Ho, 4%Y∶CaF₂ crystals were tested and analyzed. The absorption cross section at 448 nm and 643 nm were 1.13×10^-20 cm² and 0.84×10^-20 cm². J-O theory was applied to analyze fluorescence properties, the intensity parameters Ω_t(t=2, 4, 6), radiative transition rates, branching ratios and radiative lifetime were calculated. Excited by 448 nm xenon lamp at room temperature, the emission cross section at 546 nm, 650 nm and 752 nm were calculated to be 10.450×10^-21 cm², 8.737×10^-21 cm² and 5.965×10^-21 cm², respectively, and the fluorescence lifetime of the Ho^{3+ 5}F₄ and ⁵F₅ level were measured to be 33.5 μs and 17.7 μs. Excited by 640 nm LD pump at room temperature, the emission cross section at 2 031 nm and 2 847 nm were calculated to be 5.375×10^-21 cm² and 10.356×10^-21 cm², respectively, and the fluorescence lifetime of the Ho^{3+ 5}I₇ and ⁵I₆ level were measured to be 4.37 ms and 1.85 ms. All results show that the porous graphite crucible TGT method could greatly improve the efficiency of screening the doping concentration of rare earth ions in crystals, and speed up the research process of the new laser crystal materials.

Key words: calcium fluoride crystal, temperature gradient technology, crystal growth, porous crucible, laser crystal, spectral property