无热透镜效应的氟化物激光透明陶瓷的设计、制备与性能研究

The mid-infrared lasers, operating in the 2.5-3μm spectral range, were the research focus in the field of solid state laser because of their potential applications in medicine, biology processing, remote sensing and pollution monitor. The thermal effect, especially the thermal lens effect of the laser gain medium materials would seriously deteriorate the output power and the beam quality, when the solid state laser was operated. The project focuses on the thermal lens effect of the laser gain medium materials for the 3μm wavelength high power solid state laser. Using the novel idea of thermal-lens-free fluoride solid-solution (Er3+:SrF2-RF3(R=La3+,Y3+)) laser ceramics, thermal lens effect could be eliminated. The control of the thermo-optical coefficient, index of refraction and thermal expansion coefficient of the materials can be achieved according to the changing of the component of the materials. At the same time, the densification process and the evolution of the microstructure with different component were investigated. Based on the thermodynamic analysis, the main defects of the ceramics can be controlled and eliminated. Furthermore, the optimal methods to improve the optical quality of the ceramics can be built, and the microstructure and the defect of the ceramics can be effectively controlled. Finally, the high optical quality fluoride solid solution laser transparent ceramics with thermal-lens-free can be fabricated successful.

2.5-3μm波段中外红激光在医学、生物工程、遥感和污染源监测等方面有着重要的应用，是目前固体激光领域的研究热点。而固体激光器运转时，激光介质的热效应，尤其是热透镜效应严重影响输出功率和输出光束质量。本项目针对3μm激光增益介质在高功率固体激光器中的热透镜效应问题，结合常用激光介质材料的性能，提出无热透镜效应的氟化物混晶（Er3+:SrF2-RF3(R=La3+,Y3+)）激光透明陶瓷思想，从激光透明陶瓷材料的组分设计着手，实现对材料的热光系数、折射率和热膨胀系数的调控，最终实现减小甚至消除固体激光器中激光介质的热透镜效应的目的。同时，系统研究不同组分的Er3+:SrF2-RF3透明陶瓷的致密化过程与显微结构演变规律，基于陶瓷烧结的热力学过程，控制并消除主要缺陷，构筑材料增透的优化途径，实现微结构、缺陷的有效调控，制备得到高光学质量的氟化物混晶激光透明陶瓷。

基于Er3+离子在2.5~3微米波段中红外激光是固体激光领域的研究热点。本项目选择声子能量低、无热透镜效应的Er3+:SrF2-RF3为基质，开展其纳米粉体的合成和致密化过程及相关性能研究。采用共沉淀法，以KF和硝酸锶为原料，在滴定速率为2.5 ml/min，陈化20 h时，合成了高纯、单分散、高烧结活性的不同Er3+浓度掺杂的氟化锶纳米粉体；利用真空热压烧结，实现了不同粉体的致密化，当烧结温度了为700℃，保温40h，成功制备高光学质量的Er3+掺杂氟化锶透明陶瓷（2.92mm），其在2000nm处的透过率达到了92%。通过对微结构演变的系统研究，通过拟合G^n-G_0^n vs烧结时间，阐明氟化锶透明陶瓷的晶粒生长机制为晶格扩散机制。此外，对Er3+掺杂的氟化锶透明陶瓷样品进行激发光谱测试，结果显示，在975nm 激光激发下，最强发射峰位于2735nm，这表明此样品有望在2.7μm处实现激光输出。在SCI期刊上发表论文3篇，申请专利2项，培养硕士研究生2名。