基于SHG/SFG-OPO的高性能可调谐可见光单频光纤激光器

High-performance fiber-based lasers tuning in the visible, which are of great scientific significance and application value, have been frontier and hotspot of current laser research. High power fiber MOPA combined with SHG/SFG-OPO is the most reliable technic to achieve this purpose. However, for most such kind systems, high pumping power have not been fully extracted and thus visible output are limited. For this reason, the idea of balanced optimizing of the two cascaded nonlinear processes are proposed herein. The theoretical model which simultaneous the couple-wave equations of both processes of intracavity SHG/SFG and parametric down conversion will be built to analyze their interaction mechanism on each other. Considering the influence of pumping, nonlinear crystal parameters, cavity structure and intracavity power intensity, the optimum condition for enhanced visible output of high power SHG/SFG-OPO can be obtained. In the experiment, high power single-frequency fiber MOPA at 1064nm and subsequent frequency-double green laser at 532nm will be build and thus high-performance SHG/SFG-OPO in visible could be realized based on them. After optimizing the efficiency of the cascaded nonlinear processes simultaneously according to the theoretical model, high-power single-frequency visible output widely tuned across important red, green and blue can be obtained.

高性能可调谐可见光光纤激光器是当前激光技术领域的前沿课题和研究热点，具有重要科学意义和实用价值。高功率光纤激光MOPA结合SHG/SFG-OPO是实现高功率宽调谐单频可见光输出的最佳技术方案。针对其可见光输出功率普遍较低的问题，本申请提出级联非线性过程转换效率平衡优化的解决方法。理论上建立SHG/SFG过程和参量下转换过程相联立的耦合波方程模型，分析二者间相互影响制约的作用机制，综合考虑泵浦、晶体参数、腔型结构、腔内功率密度等因素对转换效率的影响，得到具有普遍意义的SHG/SFG-OPO优化条件。实验上搭建高功率1064nm单频光纤MOPA并高效倍频产生532nm单频绿光，以此为基础实现基于SHG/SFG-OPO的高性能可见光单频光纤激光器，根据理论模型对级联非线性过程转换效率进行主动调控以实现同时优化，获得覆盖红、绿、蓝等主要波段的高功率、宽调谐单频可见光输出。

可见光波段激光器在军事、民用以及前沿科学研究等领域具有重要应用。本项目将高功率光纤激光器与非线性频率变换技术相结合，以高性能光纤激光器作为泵浦源，以光学参量振荡器内腔倍频/和频为主要技术手段，能够在保持光纤激光单频特性的同时，通过优化级联非线性过程的转换效率，实现覆盖红、绿、蓝等可见光波段的高功率可调谐光纤激光输出。.本项目围绕这一目标开展了以下工作：.1．采用三级全光纤MOPA结构对1064nm单频种子源进行放大，通过求解增益光纤内部的功率传输方程，得到各放大级增益光纤的最佳长度，结合实验结果优化各放大级结构，有效地抑制了ASE和SBS效应的产生。主放大级最高输出功率为114W，此时的线宽为62.65kHz，光束质量M2<1.2。.2．利用外腔谐振倍频技术，对百瓦级1064nm光纤激光进行高效倍频，获得了最高功率为55.69W，光束质量M2≈1.2的单频532nm绿光输出。.3．以高功率532nm单频绿光泵浦PPLT-OPO，产生位于800—960nm波段的信号光，通过对该信号光进行内腔倍频，获得了波长输出范围覆盖400—480nm，最高5.31W的蓝紫激光输出，线宽为8.39MHz，光束质量M2<1.3。.4. 以百瓦级1064nm光纤激光泵浦PPLN-OPO，产生位于1280—1600nm波段的信号光，通过对该信号光进行内腔倍频以及与1064nm泵浦光和频，获得了波长输出范围覆盖580—750nm，最高10.44W的黄红激光输出，线宽为8.46MHz，光束质量M2<1.3。.通过本项目的研究，实现了覆盖红、绿、蓝等主要波段的高性能可调谐可见光纤激光输出，拓展了高性能光纤激光器的工作波长，提升了可调谐可见光纤激光器的性能。.项目执行过程中共发表期刊论文13篇，其中SCI收录8篇，EI收录13篇，申请发明专利5项。毕业博士生1名，硕士生4名。