窄线宽光纤放大器中多频段相位噪声特性和光反馈主动线性锁相机理的研究

High-power narrow-linewidth fiber lasers, featuring high conversion efficiency, compact construction and low cost, have great research prospect and widespread applications. Especially, in many precision researches such as large laser interferometric gravitational-wave detection, coherent beam combining, and transfer of optical frequency they are used as essential optical sources and have been an international hotspot. Aiming for these high-power fiber lasers with narrow linewidth, analysis and measurement of phase noise in optical amplifiers, especially its originations, characteristics, and spectrum are perfectly necessary and critical route. High-precision phase locking among narrow-linewidth lasers is the principal technique to obtain high-power narrow-linewidth laser sources. Meanwhile, the characteristics of the phase noise are also the dominant causes to determine effect of phase locking. In multi-beam laser phase locking passively optical feedback and actively phase locking techniques which have individual advantages have been respectively investigated and separately realized for suppressing phase noise. In this project originations and characteristics of multiband phase noise in fiber lasers and amplifiers are investigated closely and measured precisely. Based on theory and the high-precision detection system of phase noise, an effective combination of passively optical feedback and actively linear phase locking is proposed to develop a novel hybrid phase locking technique and explored its intrinsic mechanism. Through phase locking multiple beams phase noise can be suppressed. This scheme can achieve high rejection ratio and wide control bandwidth for phase noise through integrating advantages of both two techniques.

高功率窄线宽光纤激光器具有转换效率高、结构紧凑、成本低等优点具有重大研究前景并被广泛应用，尤其在大型激光干涉引力波探测、相干光束合成、光频传输等精密科学领域中，它作为基本光源已成为国际研究的热点。为获得高功率窄线宽激光，对光放大器中相位噪声的分析和探测是的十分必要且关键的途径，特别是其来源、特性和频率谱分布。窄线宽激光的高精度锁相则是获得这种光源的主要技术手段，同时激光相位噪声特征也是决定锁相效果的重要因素之一。在激光锁相进行噪声抑制上，被动光反馈和主动锁相技术各具优势，作为主流技术而被分别研究和独立实现。本项目针对光纤激光及放大系统中不同频段相位噪声的来源和特性进行研究和精密测量。基于理论分析和高精度相位探测装置，将环形腔光反馈和主动线性锁相进行结合，探索和研究新型的混合锁相过程的机理，来进行多路激光锁相和噪声抑制。该方案结合了两种技术的优点，能获得更宽的控制带宽和高的噪声抑制比。

高功率窄线宽光纤激光器具有转换效率高、结构紧凑、成本低等优点具有重大研究前景并被广泛应用，尤其在精密科学领域中，它作为基本光源已成为国际研究的热点。为获得高功率窄线宽激光，对光放大器中相位噪声的分析和探测是的十分必要且关键的途径，特别是其来源、特性和频率谱分布。窄线宽激光的高精度锁相则是获得这种光源的主要技术手段，同时激光相位噪声特征也是决定锁相效果的重要因素之一。.本项目首先通过理论建模研究光纤激光及其放大系统中的相位噪声特性，分析了环境振动、温度、ASE和非线性效应对激光相位噪声的贡献，并搭建实验装置对输出激光的频率/相位噪声和光谱特性进行实际测量。对低噪声窄线宽单频激光器进行功率放大，获得了高信噪比输出的线偏振激光，输出激光功率达到12W，光谱线宽为353kHz，偏振消光比高于20dB，信噪比≥50dB。第二，设计光学零差和外差拍频相位检测装置，建立了相位噪声探测的模型，分析了两者的优缺点。基于光外差相位探测技术，建立从一路到三路的光学锁相环。设计反馈控制电路，分析和优化系统的环路响应，使得控制带宽达到66kHz。实现了三路激光相干合成的原理验证，合束激光的偏振消光比达到17.44dB。第三，建立环形腔光反馈激光器的注入锁定的理论模型，详细分析了主从激光器相位噪声对输出激光的传递情况。实现了多路环形腔光反馈的注入锁定，研究在有无种子激光注入锁定下的光谱特性、功率噪声和偏振特性。结合环形腔激光的注入锁定和主动外差锁相控制系统实现了混合锁相控制和偏振合成。三路混合锁相控制的偏振光束合成的消光比>15dB，相位噪声约10-6rad/Hz1/2，在测量频率范围内相位噪声优于λ/15。最后对系统中影响偏振消光比的因素进行详细分析。.对高功率窄线宽光纤激光器相位噪声特性和混合锁相控制的研究和分析，有利于获得更宽的锁相控制带宽和高的噪声抑制比，应用于偏振光束合成，获得高亮度激光光源。该光源能应用于大型激光干涉引力波探测、冷原子物理和激光通信等领域。