| 题名 | RE3+(RE=Yb、Sm、Dy):GdVO4激光晶体的生长与光谱性能研究 |
| 作者 | 何晓明 |
| 学位类别 | 硕士 |
| 答辩日期 | 2008 |
| 授予单位 | 中国科学院上海光学精密机械研究所 |
| 导师 | 张连翰 |
| 关键词 | Yb:GdVO4 Sm:GdVO4 Dy:GdVO4 激光晶体 光谱性能 |
| 其他题名 | Study on growth and spectrum properties of RE3+(RE=Yb, Sm, Dy):GdVO4 laser crystal |
| 中文摘要 | 激光二极管泵浦源的技术进步，极大的推动了固体激光器件、技术及应用的发展，使得激光器向着全固化、小型化、可调谐、高效率方向发展。钒酸钇晶体作为钒酸盐晶体中的典型代表，得到广泛而深入的研究。然而，与目前广泛应用的钒酸钇晶体相比，以钒酸钆晶体为基质的激光晶体具更大的受激发射截面；在泵浦波段有宽吸收带；对泵浦波长和二极管温度控制依赖低；高热传导率。这表明，钒酸钆晶体是具有潜在应用价值的优良激光基质材料。 本文系统研究了Yb3+ 、Sm3+和Dy3+三种稀土离子掺杂GdVO4激光晶体的生长、结构特性和光谱性能，主要结论如下： 1. 采用提拉法生长了10at.％Yb:GdVO4、2at.％Sm:GdVO4和5at.％Dy:GdVO4三种晶体，通过优化生长工艺，得到透明、高光质量、完整不开裂的晶体。通过XRD分析确定了它们的晶体结构及掺杂对晶胞参数的影响，并计算了其晶胞参数，通过ICP技术测定了Yb3+、Sm3+和Dy3+三种离子在GdVO4晶体中的分凝系数，并通过激光脉冲法测量了10at.％Yb:GdVO4晶体不同轴向的热导率，与Yb:YAG晶体相比，随Yb离子掺杂浓度增加Yb:GdVO4晶体的热导率下降慢。 2. 研究了Yb:GdVO4晶体在室温下的偏振吸收、偏振发射光谱和荧光寿命，我们发现Yb:GdVO4晶体具有很强的偏振特性，π偏振吸收截面、发射截面和荧光强度都远大于σ偏振，π偏振荧光寿命较长。与相同浓度Yb:YAG晶体相比，Yb:GdVO4晶体具有大的吸收、发射截面，具有更宽的吸收带宽，宽的吸收带有利于InGaAs LD有效抽运，并且降低了对LD泵浦源温度控制的要求，容易实现激光振荡；同时Yb:GdVO4晶体具有宽的荧光发射，适合于飞秒激光领域的应用。 分析了Yb:GdVO4晶体上转换荧光，我们认为除496nm处荧光峰是由Yb3+离子的合作发光造成外，其它所有荧光峰是由Yb3+离子与Tm3+、Eu3+ 和Ho3+杂质离子的能量传递发光产生，文中对上转换荧光光谱中所有荧光峰做了解释，并阐述了Yb3+离子与它们之间的能量传递机制。 3. 测量了室温下Sm:GdVO4晶体和Dy:GdVO4晶体的吸收光谱、激发光谱和荧光光谱。运用JO理论，通过吸收光谱获得跃迁强度参数Ωi，由此计算了跃迁几率、荧光分支比 、辐射寿命、发射截面等光谱参数。 Sm:GdVO4晶体中三个强度参量分别为：Ω2＝2.75×10-19cm2，Ω4＝3.22×10-20 cm2，Ω6=4.97×10-20cm2，在408nm处收吸收截面为3.87×10-20cm2，以此激发获得604nm最强荧光峰，对应于4G5/2 →6H7/2跃迁，发射截面为7.62×10-21cm2，是Sm:YAP晶体的4.4倍，στ＝4.11×10-21cm2ms，结果表明Sm:GdVO4晶体中4G5/2→6G7/2是比较有可能实现红光激光输出的跃迁。 Dy:GdVO4晶体中三个强度参量分别为：Ω2＝2.48×10-18cm2, Ω4＝1.21×10-18 cm2和Ω6=2.08×10-19cm2，对应于4F9/2→6H13/2的跃迁575nm的荧光半峰宽为7.6nm，其发射截面为25.9×10-20cm2，容易实现黄光激光输出。理论上计算了1.8μm 的6H11/2→6H15/2跃迁、2.9μm的6H13/2→6H15/2跃迁的激光参数。 与其它掺同种稀土离子材料相比，掺Sm3+和掺Dy3+离子的GdVO4晶体Ω2都要大很多，这说明在掺稀土离子的GdVO4晶体中，RE3+－O键的共价性很强。同时我们给出了室温下Sm:GdVO4和Dy:GdVO4晶体中的跃迁机制。 |
| 英文摘要 | The development of laser diode pump source technology greatly accelerates the evolution of solid state laser devices, corresponding technology and applications, which in turn directs the lasers to solidification, miniature, tunablity and high efficiency. Yttrium vanadate (YVO4) single crystal, as a typical member of vanadate single crystals, has been widely and deeply investigated due to its excellent performance in the optical communication. However, compared with YVO4, the laser crystals with gadolinium vanadate (GdVO4) crystal as the host possess many advantages such as larger emission cross section, boarder absorption band which decreases requirements for temperature control over LD source and higher thermal conductivity. Hence, GdVO4 single crystal indicates potential application in lasers. This paper focus on the growth, structure and spectral properties of the GdVO4 crystal doped with Yb3+, Sm3+ and Dy3+. Several conclusions were reached: 1. 10at.％Yb:GdVO4、2at.％Sm:GdVO4 and 5at.％Dy:GdVO4 were successfully grown by the Czochralski (Cz) method, by optimizing the growth process, transparent, high optical quality, free from cracking crystals were got. Crystal structures and cell parameters were determined and analyzed by XRD; influences of dopants concentration on crystal structure and cell parameters were also studied. We measured the segregation coefficient of Yb3+, Sm3+ and Dy3+ in GdVO4 crystals by ICP and the thermal conductivity of 10at.％Yb:GdVO4 crystal by laser plus. Compared with the Yb:YAG crystal, the thermal conductivity of Yb: GdVO4 crystal decreases slowly with the increase of Yb-doped concentration. 2. Polarized absorption spectra, emission spectra and fluorescence lifetime of Yb:GdVO4 crystal were measured at room temperature. It shows that Yb:GdVO4 crystal has strong polarization characteristics, the absorption and emission cross-section, fluorescence intensity and lifetime of the π polarization are much larger than that of the σ polarization. Compared with the same doped concentration of Yb:YAG crystal, the Yb:GdVO4 crystal shows larger absorption and emission cross-section and broader absorption band, which match well with the emission wavelength of efficient diode-pumping of high performance InGaAs laser diodes. The crystal also decreases requirements for temperature control over LD pumping source and facilitates laser oscillation. At the same time the crystal shows broad fluorescence emission which can used in femtosecond laser. Upconversion fluorescence of Yb:GdVO4 crystal was analyzed, the peak at 496nm is attributed to the cooperative luminescence of Yb3+, all the other peaks are attributed to the energy transfer of Yb3+ and the impurities: Tm3+, Eu3+ and Ho3+, the mechanism of energy transfer of Yb3+ and the impurities was stated in detailed. 3. Absorption, excitation and fluorescence spectra of Sm:GdVO4 and Dy:GdVO4 crystals were measured at room temperature. Through the absorption spectra, JO parameters Ωi were got, from which the spontaneons transition probabilities, the branching rations and radiative lifetime were calculated. The emission cross sections were also calculated. In Sm:GdVO4 crystal, the JO parameters were calculated as: Ω2＝2.75×10-19cm2，Ω4＝3.22×10-20 cm2，Ω6=4.97×10-20 cm2. The absorption cross-section at 408nm is 3.87×10-20cm2. Under the exciting at 408nm, the emission cross-section at 604nm in Sm:GdVO4 is 4.4 times lager than that in Sm:YAP. The product of the lifetime of 4G5/2 and the emission cross-section at 604nm is 4.11×10-21cm2ms, which indicated that the Sm: GdVO4 crystal has potential use in visible laser area. The JO parameters of Dy:GdVO4 crystal were calculated as: Ω2＝2.48×10-18cm2, Ω4＝1.21×10-18cm2 and Ω6=2.08×10-19cm2. The prominent emission peaks at the 575nm, which has the FWHM of 7.6nm and the emission cross section of 25.9×10-20cm2, is produced by the 4F9/2→6H13/2 transition. So this transition is very suit for yellow laser output. The laser parameters of emission peaks at 1.8μm of the 6H11/2→6H15/2 transition and 2.9μm of the 6H13/2→6H15/2 transition is also calculated in theory. Compared with the same dopants of Sm3+ and Dy3+, the Ω2 of GdVO4 crystal is much larger. It indicates that in the GdVO4 crystal doped with rare earth ion, the covalent bonds of RE3+－O are very strong. Meanwhile the transition mechanics of Sm:GdVO4 and Dy:GdVO4 are presented. |
| 语种 | 中文 |
| 内容类型 | 学位论文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/16632]  |
| 专题 | 上海光学精密机械研究所_学位论文 |
| 推荐引用方式 GB/T 7714 | 何晓明. RE3+(RE=Yb、Sm、Dy):GdVO4激光晶体的生长与光谱性能研究[D]. 中国科学院上海光学精密机械研究所. 2008. |
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