多孔坩埚温度梯度法生长Ho,Y∶CaF2晶体及其光谱性能

采用自主设计改造的温梯炉,成功生长了不同浓度Ho³⁺、Y³⁺掺杂的CaF₂及Sr_xCa_1-xF₂晶体,晶体尺寸约为?15 mm×55 mm,生长周期约为6 d,能够实现7种不同浓度晶体的同步生长,并选取其中的4%(原子数分数)Ho,4%Y∶CaF₂晶体进行分析,吸收测试表明,该晶体448 nm和643 nm处吸收峰的吸收截面分别是1.13×10^-20 cm²和0.84×10^-20 cm², J-O理论分析得到了晶场强度参数Ω_t(t=2、4、6)、辐射跃迁几率、荧光分支比和辐射寿命。在448 nm氙灯激发下,经计算得到该晶体在546 nm、650 nm 和752 nm处的发射截面分别为10.450×10^-21 cm²、8.737×10^-21 cm²和5.965×10^-21 cm²,测得⁵F₄和⁵F₅能级的寿命分别为33.5 μs和17.7 μs。在640 nm LD泵浦激发下,经计算得到该晶体2 031 nm处发射截面为5.375×10^-21 cm²,2 847 nm处发射截面为10.356×10^-21 cm²,测得⁵I₇和⁵I₆ 能级的寿命分别为4.37 ms 和1.85 ms。以上结果表明,多孔坩埚温梯法能够大大提高激光晶体稀土离子掺杂浓度筛选的效率,加快新型激光晶体材料的研发速度。

Growth and Spectral Properties of Ho,Y∶CaF2 Crystal Grown with Porous Crucible TGT Method

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 ?15 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.