多路超窄线宽激光放大及控制技术研究

On the basis of No. 22 subject with certain target of NSAF, which is named "Research of amplification and control of multi-channels ultra-narrow linewidth lasers", this application proposals that multi wavelength seed is synchronously generated in a single resonator by multi-wavelengths fiber Bragg grating. We will use MOPA technology to achieve fiber-Nd:YAG slab multi-stages amplification and obtain high power laser. In the process of amplification, wavefront and phase will be monitoried from time domain, space domain, and frequence domain. The phase distortion of multi-channels amplifiers will be suppressed to achieve the high power high beam quality in phase light source which is required by large number coherent beam combining solid laser system. Research on laser materials, principle schemes, and key technologies will be started. Some physical problem with profound academic value will be studied, such as: the synchronous mechanism of multi-wavelengths radiation in a single resonator, Stimulated Brillouin Scattering in narrow linewidth high power amplfication, et al. The beam control technology will be developed in time domain, space domain, and frequency domain. Basic research, technology development, and Practical application will be integrated. This project will promote high brightness high energy solid laser system to practical application.

根据NSAF联合基金“明确目标课题”之（22）“多路超窄线宽激光放大及控制技术研究”所规定的研究内容，本申请书提出“采用多波长光纤光栅对由同一谐振腔共腔产生时序同步多波长种子源”，结合MOPA技术全光纤-Nd：YAG板条级联放大技术产生高功率激光，在逐级放大过程中，从“时”、“空”、“频”域三方面综合监测激光波前和相位等特性，并结合抑制手段有效控制多路放大模块的相位畸变，使之能够达到实现多光束相干合成高亮度固体激光系统所需的高功率高光束质量相位同步的光源要求。开展激光材料、原理方案、关键技术等方面的基础研究，从中提炼出系列具有深刻学术意义的物理问题，如多波长共腔辐射时序同步机理、窄谱线高功率光纤放大SBS效应、等，进一步发展相关光束的时间、空间和频谱控制技术，形成了基础性研究、高技术研发与实用化应用的有机结合。有望成为推动高亮度高能固体激光系统走向实际应用的有效途径。

本项目详细研究了多路超窄线宽激光放大系统及其控制技术。在理论上分析了高功率光纤放大器的基本结构和光放大原理，建立相关理论的模型，仔细研究了光纤激光放大器中的非线性效应如受激拉曼散射、受激布里渊散射（SBS）等对光纤放大器功率提升的影响，特别是窄线宽激光放大器中SBS阈值与种子激光的线宽的关系。基于SBS的理论计算，在实验上利用主振荡器光放大技术实现了对经过光场相位精密调控后的三波长等强度的窄线宽激光（线宽为3.76MHz）的光纤放大，研究了三路激光的频率间隔与SBS阈值的关系。通过优化频率间隔到2GHz有效的提高了SBS阈值，获得101.8W的窄线宽激光输出，光束质量为M2=1.06，线偏振态的偏振消光比为17.3dB。通过对该系统的研究，将有利于高功率超窄线宽光纤激光器的研制和激光光束的相干合成。