【作者】 张天庆；

【导师】 曾繁明；

【作者基本信息】 长春理工大学 ， 材料科学与工程， 2023， 硕士

【摘要】 近年来,激光二极管（LD）泵浦的全固态激光器已成为激光领域中最具发展前景的研究方向之一,并且由于它具有输出功率稳定、效率高等优点,已逐渐成为理想的新型相干光源。激光工作物质是固态激光器的核心,探索适合LD泵浦的激光工作物质是提高激光器效率的关键。Na Gd（WO₄）₂（NGW）是一种典型的激光晶体材料,尤其是稀土掺杂的NGW晶体,具有较宽的吸收峰、较低的阈值和较长的荧光寿命,利用这些特点可以实现激光器的全固化和小型化。在本研究中,通过Y³⁺离子取代NGW基质中部分Gd³⁺离子,形成NYGW混晶,提高了NGW晶体的无序度,同时由于非均匀加宽效应,使得稀土离子的吸收和发射光谱谱线展宽。混晶也会增大单晶的比热容,这些特性会提高激光器对泵浦光的利用,进而提升激光器的效率。本文以Nd:NYGW和Yb:NYGW晶体为研究对象,详细研究了其生长工艺和光谱性能,并通过光谱参数预测了晶体的激光性能。主要研究内容如下:（1）通过高温固相法和水热法分别合成了NYGW多晶料,对比了两种方法合成的多晶料的纯度,获得最佳的合成工艺和多晶原料纯化技术。（2）研究了NYGW晶体的生长原理与工艺,并系统地讨论了影响晶体质量的因素。以高纯的Na₂CO₃、WO₃、Y₂O₃及Gd₂O₃为原料,通过提拉法成功生长了高质量的NYGW晶体,结果表明其结构与NGW晶体一致(空间群为I_41/a),未发生相变。（3）采用提拉法成功生长了不同浓度Nd³⁺离子掺杂的NYGW晶体。XRD结果表明,Nd:NYGW晶体仍属于四方相结构。分析了Nd:NYGW晶体的吸收光谱,通过J-O理论计算了晶体的J-O强度参数。测量了808 nm激发下Nd:NYGW晶体的近红外发射光谱,计算了Nd:NYGW晶体的吸收和发射截面,其中808 nm处最强吸收截面为2.34×10^-20 cm²,1064 nm处最强发射截面为6.68×10^-20 cm²。Nd:NYGW晶体的发射截面较大,更有利于实现激光输出。（4）采用提拉法成功生长了不同浓度Yb³⁺离子掺杂的NYGW晶体,物相结构表明,Yb³⁺离子的掺杂并没有改变NYGW晶体的四方相结构。研究了晶体的光谱特性,Yb:NYGW晶体的吸收峰位于976 nm处,计算得到Yb:NYGW晶体的最大吸收截面为2.06×10^-20 cm²。Yb:NYGW晶体的发射带位于980 nm-1100 nm处,计算得到Yb:NYGW晶体的最大发射截面为1.66×10^-20 cm²。计算了晶体的增益截面,较低的反转水平意味着Yb:NYGW晶体的泵浦阈值较低。这些结果都表明,Yb:NYGW晶体在近红外领域具有极高的应用潜力。更多还原

【Abstract】 In recent years,the all-solid-state laser pumped by the laser diode（LD）has become one of the most promising research directions in the laser field,and because of its stable output power and high efficiency,it has gradually become an ideal new coherent light source.The laser working substance is the core of the solid-state laser.Exploring the laser working substance suitable for LD pumping is the key to improving the efficiency of laser.Na Gd（WO₄）₂（NGW）is a typical laser crystal material,especially the rare earth doped NGW crystals,which has a wide absorption peak,low threshold and long fluorescence lifetime,which can be used to achieve full solidification and miniaturization of lasers.In this study,some Gd³⁺ions in the NGW matrix were replaced by Y³⁺ions to form NYGW mixed crystals,which improved the disorder of the NGW crystals and widened the absorption and emission spectrum lines of rare earth ions due to the non-uniform broadening effect.Mixed crystals also increase the specific heat capacity of single crystals.These properties will improve the utilization of the laser pump light and thus improve the efficiency of the laser.In this paper,Nd:NYGW and Yb:NYGW crystals are taken as the research object,the growth technology and spectral properties of the crystals are studied in detail,and the laser properties of the crystals are predicted by spectral parameters.The main research contents are as follows:（1）The high purity NYGW polycrystalline materials were synthesized by high temperature solid phase method and hydrothermal method respectively.The purity and properties of the polycrystalline materials synthesized by the two methods were compared,and the best synthesis process and purification technology of polycrystalline materials were obtained.（2）The growth principle and technology of NYGW crystal are studied,and the factors affecting crystal quality are discussed systematically.NYGW crystals with high purity Na₂CO₃,WO₃,Y₂O₃ and Gd₂O₃ were successfully grown by pulling method.The results show that the structure of NYGW crystals is consistent with that of NGW crystals(space group I_41/a)without phase transition.（3）NYGW crystals doped with different concentrations of Nd³⁺ions were successfully grown by lifting method.XRD shows that Nd:NYGW crystal still belongs to tetragonal phase structure.The absorption spectra of Nd:NYGW crystals are analyzed and the J-O intensity parameters are calculated by the J-O theory.The NIR emission spectra of Nd:NYGW crystal excited at 808 nm are measured,and the absorption and emission cross sections of Nd:NYGW crystal are calculated.The maximum absorption cross section at 808nm is 2.34×10^-20 cm²,and the maximum emission cross section at 1064 nm is 6.68×10^-20 cm².Nd:NYGW crystals have larger emission cross section,which is more conducive to realizing laser output.（4）NYGW crystals doped with different concentrations of Yb³⁺ions were successfully grown by lifting method.The phase structure showed that the doping with Yb³⁺ions did not change the tetragonal phase structure of the NYGW crystal.The absorption peak of Yb:NYGW crystal is located at 976 nm,and the maximum absorption cross section of Yb:NYGW crystal is 2.06×10^-20 cm².The emission band of Yb:NYGW crystal is located at 980nm-1100 nm,and the maximum emission cross section of Yb:NYGW crystal is calculated to be 1.66×10^-20 cm².The gain cross section of the crystal is calculated and a lower inversion level implies a lower pumping threshold for the Yb:NYGW crystal.All these results indicate that Yb:NYGW crystals have high application potential in the near infrared field.更多还原