高功率连续掺镱光纤激光器输出光谱展宽特性与谱宽控制研究

High power continuous fiber laser has grown deep and had wide application in fields such as industry, defense and manufacture. And there has been a growing demand for the output laser power. However, the output power of single fiber output laser is limited. Therefore, spectral beam combining is an effective method to further raise the laser power. Since the relatively low output power of sub-beam single narrow-linewidth fiber laser, the spectrum width of broad spectrum sub-beam fiber laser with higher output power potential should be narrowed, laying foundations for wavelength division multiplexing fiber laser spectral beam combining.Currently the study on the spectrum of single fiber broad spectral width high power laser has been lacking. The mechanism and the features of spectrum broadening during the laser power amplification process with different broad linewidth seed have not yet been clear. This project plans to develop deep and systematic study on the mechanism and the features of the spectrum broadening, the features of Raman fiber laser spectrum, and fiber laser spectrum control methods in the high power broad spectrum double clad Yb-doped fiber laser. Based on spectrum broadening mechanism, dynamic process, as well as the theoretical analysis and experiments on spectrum features, an effective approach to control output spectrum width of high power fiber laser should be proposed.

高功率连续光纤激光器在工业、国防、装备制造等方面应用日趋深入，对激光输出功率提出了越来越高的要求，然而单纤激光输出功率有限，光谱合成是进一步提升功率的有效手段。但由于子束窄线宽光纤激光器输出功率较低，需要在具有更高输出激光功率潜质的宽谱子束光纤激光器中进一步压缩光谱宽度，为波分复用光纤激光光谱合成奠定基础。目前，对单纤宽谱高功率光纤激光器光谱性能研究缺乏，在不同宽谱种子注入下的激光功率放大过程中，光谱展宽机理尚不明确，展宽特性不清晰。本项目拟对高功率宽谱双包层掺镱光纤激光器输出光谱展宽机理与特性开展深入系统地研究。具体包括高功率宽谱光纤激光器在中心波长附近光谱展宽机理与特性研究、拉曼光谱特性研究以及光谱控制方法研究。结合光谱展宽的原因、动力学过程以及特性的理论分析和光谱特性实验研究，提出高功率光纤激光器控制输出光谱宽度的有效方法。

本项目围绕高功率连续掺镱光纤激光器输出光谱展宽特性与谱宽控制进行了深入的理论和实验研究。建立了光纤激光种子源时域特性、高功率宽谱光纤激光器和以广义的非线性薛定谔方程为基础的随机光纤激光器光谱展宽理论模型，建立了高功率光纤激光器包含拉曼非线性效应的Yb-拉曼混合增益分析模型。在此基础上，研究了高功率宽谱光纤激光器光谱展宽的特点，阐明了光纤激光器中心波长与相关拉曼波长光谱演变的机理和规律。理论和实验表明随机光纤激光器相比光纤光栅固定腔光纤激光器具有更好的时域特性，是有效抑制光谱在后续放大中展宽的方法。提出了控制连续高功率宽谱光纤激光器中心波长光谱宽度以及抑制拉曼的有效方法。基于光谱控制方法，实现了高光谱纯度5kW随机光纤激光器、基于光纤光栅种子源的3kW高功率谱密度窄线宽光纤激光器。论证了基于随机光纤激光器种子源的高功率光纤放大器在10kW功率下实现光谱带宽3nm@10dB的可行性，给出了高功率随机光纤激光器设计方案，为波分复用光纤激光光谱合成奠定了基础。项目成果对我国进一步实现自主可控的高功率光纤激光光源有重要意义，成果将应用于工业、国防和装备制造等领域。