准四能级低阈值掺镱硅酸钪激光特性研究

Laser diode pumped high power solid state laser is widely employed in the areas of Optoelectronics Countermeasure, Laser Fusion Ignition and Isotope Separation. High power laser system has high requirement on thermal and mechanical properties of laser gain materials. Sc2SiO5 crystal possesses high thermal conductivity (κ = 7.5 W·m-1·K-1） and minus colarescence coefficient (dn/dT = -6.3×10-6 K-1）. By strong coupling between ytterbium ions and crystal field, quasi-four level Yb:Sc2SiO5 single crystal were grown with large energy stark splitting (1027 cm-1) which is beneficial for releasing thermal block during high power laser operation. Encouraged by primary realization of low threshold and high power laser based on Yb:Sc2SiO5 gain crystal, we propose large sized and bonded Yb: Sc2SiO5 crystal with the advantage of thermal compensation for high power laser operation. The thermal and mechanical properties of Yb:Sc2SiO5 crystal in high power laser system will be systematically studied. The proposal aims to offer important supporting data for building up new type of high power solid state laser based on Yb:Sc2SiO5 gain crystal. The project is expected to open a new research direction of quasi-four-level gain materials for low threshold and high power laser system.

二极管抽运的紧凑型高功率固体激光器在光电对抗、激光软硬杀伤、激光点火核聚变、同位素分离等领域具有广泛的应用前景。高功率激光系统对增益介质材料的热力学性能提出了较高的要求。硅酸钪晶体具有负热光系数dn/dT（-6.3×10-6 K-1）、热学性能佳κ（7.5 W·m-1·K-1）的特征。本申请项目通过设计镱离子与晶体场的强场耦合作用，初步生长获得具有大的下能级分裂（1027 cm-1）的掺镱硅酸钪晶体，可有效缓解能级通道中的热阻塞效应，并初步实现低阈值高功率准四能级激光输出。基于以上结果，本项目首次提出掺镱硅酸钪晶体及其复合结构晶体作为研究对象，系统性地掌握掺镱硅酸钪激光晶体参数、光学性能、热力学特性和激光特性，为掺镱硅酸钪激光晶体作为高功率固体激光增益介质的可行性提供支撑数据。本申请项目的开展，有望为低阈值高功率固体激光领域的增益介质研究开拓新的方向。

二极管泵浦高功率固体激光器在光电对抗、激光冲击强化等领域具有广泛应用前景。高功率激光系统对增益介质的热力学性能提出了较高要求。本研究设计了镱离子与晶体场强场耦合作用，通过调整温场结构、优化生长工艺，有效控制了晶体生长速率及生长界面稳定性；采用提拉法制备了高光学质量、下能级分裂值为1027 cm-1的准四能级Yb:Sc2SiO5晶体，毛坯直径53 mm、长度180 mm，光学均匀性1.9x10-6，断裂韧性0.83 MPam1/2，抗折强度135.5 MPa。通过调整激光谐振腔内模式匹配，实现低阈值高功率准四能级激光输出，斜效率达到70%。进一步设计通过稀土离子间能级转移，增加了吸收截面与发射截面，制备了Yb,Nd:Sc2SiO5激光晶体实现连续激光输出、斜效率63%。采用室温键合技术成功制备出蓝宝石/Yb3+:Sc2SiO5、蓝宝石/Nd:YAG（晶体、陶瓷）复合激光材料，并开展了相应的激光特性研究，论证了复合激光材料可有效降低激光谐振腔内热效应。综上，本研究着眼于降低谐振腔内热效应，系统性开展了Yb:Sc2SiO5的晶体参数、光学性能、热力学特性和激光特性研究、及室温键合技术制备复合激光增益介质，为开拓新型高功率固体激光增益介质提供支撑数据。室温键合对实现特殊结构的高功率激光增益介质具有非常重要的推动作用。达到预期研究目标。