双波长级联泵浦Er3+掺杂氟化物晶体3.5μm中红外激光特性研究

3.5μm波段中红外激光在大气遥感、环境监测及光电对抗等领域具有重要应用。直接泵浦固体激光因结构简单、成本低廉等优点成为3.5μm波段中红外激光领域的研究热点。目前，Er3+:ZBLAN光纤激光器已实现3.5μm波段激光效运转，但存在光纤制备工艺复杂、机械强度低等问题。Er3+掺杂氟化物晶体制备工艺成熟，声子能量更低，更有利于降低无辐射跃迁几率，加上固体介质储能性好、非线性效应小等优势，成为有潜力产生3.5μm波段中红外激光的理想工作介质。然而，截止目前尚未有Er3+掺杂3.5μm固体激光的研究报道。本项目以Er3+掺杂氟化物晶体为研究对象，深入研究激发态吸收、无辐射跃迁衰减等关键科学问题，利用双波长级联泵浦技术建立4I11/2虚拟基态能级，抑制激发态吸收，实现高效3.5μm激光振荡，探索脉冲激光运转可行性，为推进直接泵浦稀土离子3.5μm波段中红外固体激光器走向实用化探索新的技术路线。

In recent years, mid-infrared laser at the wavelength of 3.5 μm has important applications in the fields of atmospheric remote sensing, environmental monitoring, and optoelectronic countermeasures. Direct-pumped solid-state lasers have become a research hotspot in the field of mid-infrared lasers at 3.5 μm due to their simple structure and low cost. At present, the efficient Er3+:ZBLAN fiber laser at 3.5 μm has achieved. But there are problems remain such as complex fiber preparation process and low mechanical strength of Er3+:ZBLAN fiber. Er3+-doped fluoride crystals possess mature preparation technology and low phonon energy, which is more conducive to reducing the probability of non-radiative transitions. Coupled with the advantages of large energy storage and small nonlinear effects, Er3+-doped fluoride crystals become an ideal working medium with potential to produce mid-infrared laser at 3.5 μm. However, there is no research report on Er3+-doped 3.5 μm solid-state laser. This project takes Er3+ doped fluoride crystals as the research object. The key scientific issues such as excited state absorption and non-radiative transition attenuation are deeply studied. The 4I11/2 virtual ground state energy level is established and the excited state absorption was inhibited by dual-wavelength cascade pumping technology, to realize efficient 3.5 μm laser oscillation, find the feasibility of pulsed laser operation, and explore new technical routes for the practical use of directly pumped 3.5 μm rare-earth ions doped mid-infrared solid-state lasers.