基于复合锁相环路的高稳频低相噪布里渊光纤激光器研究

Laser-technique based space exploration is an important direction for the development of space science, and it places extremely high demands on the coherence of laser sources. At present, the phase noise and frequency instability of commercial lasers restrict the precision and resolution of laser detection, and it is urgent to realize a laser with both low phase noise and high frequency stability at the same time. This project is aimed at high-precision space laser detection, focusing on achieving the long-term frequency stability and phase noise suppression of Brillouin fiber lasers. We propose a high-precision monitoring of resonant cavity length and a phase-locking control method based on dual-optical phase difference measurement, enabling the long-term frequency stability of the Brillouin laser. We also propose a pump phase-locking control method by discriminating the phase of the beating signal of the Brillouin pump and the Stokes light, leading to a large suppression of the laser phase noise. This project locks the entire laser system to the highly-stable atomic clock, which results in a Brillouin fiber laser with low phase noise and high frequency stability simultaneously. Finally, the Brillouin fiber laser with the same stability as an atomic clock, a linewidth of sub-Hz, low phase and intensity noise is realized and it provides important support for China’s space laser exploration.

激光空间探测是空间科学发展的重要方向，其对激光源的相干性提出了极高的要求。目前商用激光器的相位噪声和频率稳定度制约着激光探测的精度和分辨率，急需解决激光器相位噪声和频率稳定度无法兼得的基础科学问题。本项目面向高精度空间激光探测需求，聚焦于布里渊光纤激光器的频率长期稳定控制和相位噪声抑制问题，提出基于双光频相位差测量的谐振腔长高精度实时检测与锁相控制方法，实现激光频率的长期稳定；提出基于泵浦光与斯托克斯光混频鉴相的泵浦光锁相控制方法，实现对输出激光相位噪声的大幅抑制。本项目将整个激光系统与高稳定原子钟频率进行锁定，攻克了布里渊光纤激光器相位噪声和频率稳定性无法同时保证的难题，最终实现稳定度与原子钟同量级、线宽在亚Hz量级、低相位和强度噪声、可满足空间高精度探测的布里渊光纤激光器，为我国空间激光探测事业提供重要支撑。

本项目围绕提升布里渊光纤激光器相干性和稳定性开展研究，以满足空间探测等应用对激光器的极高要求。为解决激光器相位噪声和频率稳定度无法兼得的基础科学问题，本项目提出了基于复合环路的布里渊激光器稳定方法，实现了布里渊激光谐振腔高精度控制和布里渊泵浦相位噪声抑制和频率稳定。最终演示了与原子钟锁定的布里渊激光器，其相干性和长期稳定性得到了显著提升。此外，项目中完成的双混频零差锁相控制技术、超稳定光频梳及其测量技术等还可用于光载微波信号高稳定分配、微波光子信号处理等多个领域。.项目共取得成果25项，其中SCI期刊论文6篇（均发表在本领域国际知名期刊如Optics Express，Optics Letters等上）,本领域国际顶级会议MWP论文3篇，申请发明专利2项，参加国际学术会议4次（共计6人次），在国内外学术会议上做邀请报告4次，培养博士研究生2名，硕士研究生4名（1名已获得硕士学位）。本项目取得了布里渊激光器关键技术的突破，获得了丰硕的科研成果，广泛开展国内外学术交流，达到预期目标，完成任务计划。