铌酸镓镧晶体生长及其中红外光参量振荡器件研究

Laser is one of the greatest inventions in the human-being history. It has been utilized in kinds of critical fields after several decades’ development. Up to now, the lasers in near infrared range have developed to maturation and thanks to the inventions and applications of series of Chinese brand nonlinear crystals, the lasers in visible and violet range are getting mature. While districted by lack of excellent nonlinear optical crystals, the lasers in mid-infrared range (3-8μm) which have many significant requirements are still in progress. The nonlinear optical crystals with low phonon energy, wide transmission range, large nonlinear coefficient and high optical damage threshold are ideal media in mid-infrared applications. Our previous fundamental study indicates that the langanite crystal possess such advantages and could be a potential mid-infrared nonlinear optical crystal. .This project will optimize the langanite crystal as the research object aiming at the desiderating in mid-infrared range, improve the crystal growth technique and the optical quality, comprehensively characterize the nonlinear optical properties, and finally realize the device design. This project is predicted to break the restrictions in the development of mid-infrared lasers and promote the evolution of the mid-infrared laser devices and techniques. .The previous study of us has realized the optical parametric generation at 4 μm which verified the feasibility of this project. The proposed study will begin with the crystal growth and proceed with the characterization of the properties and device design. All the research details are linked with each other and possess significantly scientific and practical meanings.

激光是人类的伟大发明，发展半个世纪来，已获得重要应用。到目前为止，近红外波段发展成熟；由于系列“中国牌”非线性晶体的发现和应用，可见到紫外波段也趋于成熟；受限于优秀的非线性光学晶体，中红外（3-8μm）波段激光有待发展且有重要需求。. 声子能量低、透过波段宽、非线性系数大、光损伤阈值高的非线性光学晶体是中红外波段的理想材料。我们的前期研究发现，铌酸镓镧晶体具有上述优点，是潜在的中红外非线性晶体。本项目面向中红外波段亟需，优选铌酸镓镧晶体为研究对象，完善晶体生长工艺，提高晶体质量，全面表征该晶体的非线性光学性能，实现其器件的设计，突破中红外波段激光发展瓶颈，推动中红外波段激光器件和技术的发展。. 我们已经进行了前期预研，实现了4μm波段光参量产生，证明的本项目的可行性。拟开展研究工作从晶体生长做起，涉及晶体表征和器件设计，研究内容环环相扣，有重要科学和现实意义。

中红外激光具有光子能量低、人眼安全、水分子吸收大等优势，在光电对抗、医学、光谱分析等众多军民两用领域具有重要应用。实现中红外激光的重要方式之一是非线性频率变换技术，其中重要的光学元件是非线性光学晶体。目前缺乏综合性能优异的中红外非线性光学晶体，探索和发展中红外非线性光学晶体具有重要的科学意义和潜在的应用价值。在前期研究的基础上，发现铌酸镓镧晶体是一种潜在的中红外非线性光学晶体。针对国内外研究现状和中红外激光重要应用需求，基于铌酸镓镧晶体的特性，在本项目中，我们采用提拉法优化铌酸镓镧晶体生长工艺，通过计算机理论模拟了晶体温场，获得了直径60mm的大尺寸、高光学质量的铌酸镓镧晶体。同时，表征了铌酸镓镧晶体的结构和光谱性能，其透过范围为0.28-7.4μm，其最大声子能量为810cm-1。利用晶体球法进一步修正了铌酸镓镧晶体的Sellmeier 方程。同时利用修正后的Sellmeier 方程计算得到了不同波长下的相位匹配曲线。同时根据相位匹配曲线，设计了晶体的切向为θ=57.9°，φ=90°（I类，o-ee）和θ=69.4°，φ=0°（II型，o-eo）的铌酸镓镧晶体器件。经过对晶体器件的优化调整，实现了I类DFG的最大输出能量为4.5 μm处的13.1 μJ，II类DFG的最大输出能量为4.56 μm处的5.7 μJ，相应的转换效率分别为0.085%和0.039%。在国内外学术刊物上发表论文12篇，申请发明专利2项，授权发明专利2项，培养研究生5名。