高功率光纤激光的输出模式分析及测量方法研究

The high average-power fiber laser with high beam quality has wide application prospects in fields of national defense and industrial processing, etc. .At present, high power fiber laser system uses large-mode-area fiber as the amplifier stage. The distribution of the output laser and the beam quality are determined by the guided mode field distributions and the power ratio.The goal of this research proposal is to study the key issues of pattern representation in large-mode-area fiber laser with high average-power.Based on the spatial coherence and spectral coherence theory, the temporal and spatial superposition of modes in optical fibers is studied, and separated eigen modes are extracted from the output laser field. Using the eigen mode field distribution and power ratio and other information, the beam quality evaluation of fiber laser can be achieved. The method of wavelength resolution measurement and dynamic measurement with time evolution is explored, and the influence of the nonlinear factors such as thermal effect, SRS and SBS on the distribution of the eigen mode field of the optical fiber is further understood. It provides the key data for the study of mode instability and beam quality control.We will set up the experimental system of optical fiber laser mode measurement and optimize the experimental parameters. We will achieve the measurements of separation mode field distribution, wavelength resolved power ratio of model components, time evolution of the model components. The results will lay the foundation the design and performance optimization of high power fiber laser.

高光束质量、高平均功率的光纤激光在国防和工业加工等领域有着广泛的应用前景。目前的高功率光纤激光系统多采用大模场光纤作为放大级，各本征模式场分布及功率占比等信息，决定了输出光场分布形态以及光束质量。本项目针对大模场高能光纤激光系统中的模式表征关键问题展开研究：基于空间相干和光谱相干理论研究光纤中模式的时间和空间叠加，探索从输出光场中提取分离本征模式的新方法，利用本征模式的场分布及功率占比等信息，实现光纤激光的光束质量评价；探索模式成分的波长分辨测量和随时间演化的动态测量方法，进一步理解热效应、SRS和SBS等非线性因素对光纤输出光场分布形态的影响规律，为模式不稳定性研究及光束质量控制提供关键数据。搭建光纤激光模式测量实验装置，优化测试参数，实现分离模式的场分布及功率占比测量、波长分辨的模式成分测量、模式成分随时间演化的动态测量。研究结果将为高功率大模场光纤激光设计和性能优化奠定基础。

本项目针对大模场高能光纤激光系统中的模式表征关键问题展开研究：基于空间相干和光谱相干理论研究光纤中模式的时间和空间叠加，探索了从输出光场中提取分离本征模式的新方法，利用本征模式的场分布及功率占比等信息，实现光纤激光的光束质量评价；探索模式成分的波长分辨测量和随时间演化的动态测量方法，为模式不稳定性研究及光束质量控制提供了关键数据。搭建kW级光纤激光模式测量实验装置，优化测试参数，实现分离模式的场分布及功率占比测量、波长分辨的模式成分测量。研究结果为高功率大模场光纤激光设计和性能优化提供了重要参考。