| 题名 | Tm:YAP和Tm:LSO两微米波段激光晶体生长、光谱和激光性能的研究 |
| 作者 | 宗艳花 |
| 学位类别 | 硕士 |
| 答辩日期 | 2007 |
| 授予单位 | 中国科学院上海光学精密机械研究所 |
| 导师 | 赵广军 |
| 关键词 | Tm3+ YAP LSO 激光晶体 晶体生长 2微米激光 |
| 其他题名 | Studies on Thulium doped YAP and LSO laser crystals in two micron region |
| 中文摘要 | 由于Tm3+具有与商用二极管匹配良好的吸收峰以及交叉弛豫量子效率接近于2的特性，掺Tm3+固体激光器是近年来2μm激光器研究的重点方向之一。正交晶系畸变钙钛矿结构YAP晶体具有优异的热力学性能，热导率与常见的YAG晶体接近，并且具有能抑制激光运转过程产生的热致双折射效应以及输出偏振激光等优点。正硅酸盐LSO晶体因其独特的低对称性单斜晶体结构，Lu3+扭曲的低对称双格位特性，为掺杂离子提供较强的晶体场和配位场，有利于掺杂离子产生大的Stark能级分裂，在发展三能级系统激光器方面具有十分重要的潜在应用价值。 本论文以Tm:YAP和Tm:LSO作为研究对象，在总结了已有报道的基础上，开展了晶体生长、性能表征和激光实验等方面的工作，主要包括两个部分的内容： 1． Tm:YAP晶体生长、光谱和激光性能研究。 采用提拉法成功生长了1at%、3at%、4at%、5at%及15at%浓度Tm:YAP晶体，晶体均具有高光质量、无宏观缺陷。通过XRD、ICP测试手段，对晶体结构及分凝特性进行了分析，并通过激光脉冲法对晶体热导率进行了测试，结果显示Tm:YAP晶体热导率随掺杂浓度增大而明显减小。 测试并分析了不同浓度Tm:YAP晶体的吸收和荧光性质以及其温度依赖特性，高浓度掺杂晶体表现出荧光淬灭现象。不同浓度的偏振荧光光谱显示在1934nm 5at%浓度E//a方向具有最大发射截面4.5×10-21cm2，并且具有宽且平坦的发射峰。 根据吸收光谱计算了Tm:YAP晶体JO参数：Ω2＝0.8×10-19cm2，Ω4＝1.6×10-19 cm2，Ω6＝1.1×10-19 cm2，均方根偏差1.51×10-22 cm2，并根据吸收与发射的交叠积分计算了Tm:YAP中能量交叉弛豫参数CD-A=1.53×10-40cm6/s，能量交叉弛豫半径为6.2Å，施主与施主离子能量转移参数CD-D=2.48×10-39cm6/s。 对3at%、4at%及5at%浓度Tm:YAP晶体进行了激光性能的测试。其中4at%Tm:YAP c向样品在泵浦功率为24W时，实现最优的激光输出，最大功率8.1W，最大斜效率达42%，激光输出波长为1.935μm。 2． Tm:LSO晶体生长、光谱和激光性能研究。 采用提拉法首次成功生长了高光学质量的4at%Tm:LSO晶体并对晶体结构及分凝特性、热导率进行了测试分析，4at%Tm:LSO晶体热导率测试为5.93 W•m-1•K-1。 通过吸收和发射谱的测试得到Tm:LSO在790nm吸收截面达3.39×10-21cm2，吸收峰半高宽13nm；1884nm处的发射截面峰值达5.5×10-21cm2，发射峰半高宽254nm，非常有利于实现宽调谐2μm激光的输出；并根据低温光谱测试分析了Tm:LSO晶体能级结构，其基态能级劈裂1093.5cm-1，接近于四能级激光系统。通过JO计算得JO参数为：Ω2＝4.6×10-19cm2，Ω4＝1.9×10-19cm2，Ω6＝1.1×10-19 cm2，3F4能级辐射寿命为2.7ms，3H4能级辐射寿命为0.32ms。 在77K低温条件下对4at%Tm:LSO晶体进行了初步激光性能测试，获得了0.6W的1.99μm激光输出，表明Tm:LSO晶体是2μm波段比较有潜力的一种激光材料。 |
| 英文摘要 | Tm3+ doped solid-state lasers in 2μm region, which can be directly pumped by commercially available laser diodes and possess high conversion efficiency due to the cross relaxation mechanism, have received much attention in recent years. Orthorhombic YAP crystal has excellent thermal and mechanical properties comparable to YAG single crystal. Furthermore, its natural birefringence permits it to reduce thermally induced birefringence and obtain polarized laser emission. Orthosilicate LSO single crystal provides a low-symmetry crystal structure and multi-type of distorted substitutional sites, which should be favourable for creating strong local crystal-field strength and resulting in large crystal-field splitting of the rare-earth dopants. Therefore, LSO crystal is a very potential material in the three-level laser systems. In this thesis, after a brief summary of the development of the solid-state lasers, especially those Tm3+ doped solid-lasers in 2μm region, we investigated the growth, spectra and laser performance of Tm:YAP/LSO crystals. The main work includes two parts: 1. Growth, spectra and laser performance of Tm:YAP crystals with various doping concentrations. Tm:YAP with 1at%、3at%、4at%、5at% and 15at% Tm3+ doping concentrationes were successfully grown by Czochralski (Cz) method, which are free from cracking and inclusions and have high optical quality. The crystal structure of the as-grown crystals was examined by XRD and the segregation coefficient of Tm3+ in Tm:YAP was measured by ICP. The thermal conductivity measurements showed that with the increase of Tm3+ concentration, the thermal conductivity of Tm:YAP decreased apparently. Absorption and luminescence properties of Tm:YAP at different temperatures and with different doping concentrations were studied. Concentration quenching was observed in the highly doped crystal. Polarized emission spectra showed 5at% Tm:YAP has the largest emission cross-section at 1934nm (4.5×10-21cm2) and the emission peak is wide and flat. Through the absorption spectra, JO parameters were calculated as: Ω2＝0.8×10-19cm2, Ω4＝1.6×10-19cm2, Ω6＝1.1×10-19cm2, with an error of 1.51×10-22 cm2. Energy cross-relaxation parameter CD-A was calculated by the integral overlap between the absorption and emission cross-sections, which was 1.53×10-40cm6/s, the critical radius of the cross-relaxation was calculated to be 6.2Å and the energy transfer parameter CD-D was deduced to be 2.48×10-39cm6/s. Laser experiments were demonstrated in Tm:YAP with 3at%、4at% and 5at% doping concentrations. The best laser performance was achieved with the c-cut 4at% samples at 1.935μm. The maximum output was 8.1W and the highest slope efficiency reached 42%. 2. Growth, spectra and laser performance of 4at%Tm:LSO crystal. Tm:LSO with high optical quality was successfully grown by Cz method for the first time as far as we know. The structure, segregation coefficient and thermal conductivity were measured and analyzed. The thermal conductivity of 4at%Tm:LSO at room temperature was measured to be 5.93 W•m-1•K-1. The absorption cross-section at 790nm was calculated to be 3.39×10-21cm2, with a Full-Width-at-Half-Maximum (FWHM) of 13nm. The emission cross-section reaches 5.5×10-21cm2 at the peak wavelength 1884nm, with a FWHM of 254nm, which is very suitable for widely tunable lasers in 2μm region. The energy-level diagram got from the low temperature spectra shows that the Stark splitting of the Tm3+ ground state reaches to 1093.5cm-1, approaching to that of four level laser systems. JO parameters were calculated to be: Ω2＝4.6×10-19cm2, Ω4＝1.9×10-19cm2, Ω6＝1.1×10-19 cm2, and the radiative lifetimes of 3F4 and 3H4 levels were calculated to be 2.7ms and 0.32ms respectively. Laser properties were examined in 4at%Tm:LSO crystal. An output of 0.6W at 1.99μm was achieved at 77K, which illustrates that Tm:LSO crystal is potential laser material in 2μm region. |
| 语种 | 中文 |
| 内容类型 | 学位论文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/16639]  |
| 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 | 宗艳花. Tm:YAP和Tm:LSO两微米波段激光晶体生长、光谱和激光性能的研究[D]. 中国科学院上海光学精密机械研究所. 2007. |
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