高功率光纤激光器在精密激光加工、激光医疗、激光武器等领域有着广泛的应用前景，是各发达国家竞相发展的前沿技术。本项目针对全光纤化高功率激光器性能进一步提升所遇到本质性关键技术问题，如模式优化选择、波长和偏振精确控制、高阶模和自发辐射噪声抑制以及谐振腔的热稳定性问题等，拟开展大芯径双包层光纤光栅模式特性及缺陷对高功率激光性能影响的相关机理问题研究。研究内容包括：分析大芯径双包层光纤光栅多模传输特性、模式选择、模式耦合和模间干涉；研究光栅制备过程中的模式缺陷和工艺缺陷（如纤芯折射率调制不均匀性、紫外辐照导致光纤脆化和损伤等）对激光谐振腔的影响以及在高功率条件下的热效应问题。建立大芯径双包层光纤光栅模式特性和高功率激光输出性能内在联系的理论模型，并进行深入的机理仿真分析和实验验证研究，为下一代全光纤化高功率激光器性能的提升提供理论依据和技术支撑。

High-power fiber lasers have a very wide application foregroud in the fields of fine laser processing, laser medicine and laser weapon, and it is an advanced technology for the developed countries. In order to solve the key problems to approve the performance of high power fiber laser, such as the laser mode choice, controlling of wavelength and polarization, compress of high order modes and ASE noise, this project will investigate the mechanism effect of the mode characteristcs and flaw in larger area double-cladding fiber Bragg grating (LADC-FBG) on the performance of high power fiber laser. The main contents include: analyzing the multi-mode characteristics, mode choice, mode coupling and mode interference; researching the effect of mode flaw and technology flaw for LADC-FBG fabrication on the laser performance and the related problems of heat effect; constructing the theoretical mode between the mode charateratic of the LADC-FBG and the laser performance. These will be a basis to set up a effective laser resonant cavity. Some theoretical simualtions and experimental analysis will be implemented in detail. The research in this project will hope to provide the theoretical basis and technical support for the performance improvement in the field of high power fiber laser.