光纤激光线宽深压缩及波长精密调谐关键技术研究

Narrow linewidth fiber lasers have become an indispensable laser light source in the field of optical communication and sensing due to the advantages of good monochromaticity, high temporal coherence and low phase noise. This project is aimed at the urgent needs of linewidth deep compression, wavelength precision tuning and efficient noise suppression, proposed by large capacity and long distance coherent optical communication, as well as ultra-long distance optical fiber sensing and microwave photonics. The Rayleigh scattering is proposed to suppress the laser linewidth as a breakthrough point, and high gain fiber with high Rayleigh scattering coefficient will be studied. An integrated Rayleigh feedback filter based on two-dimensional material and the in-fiber whispering gallery mode filter, and an integrated micro ring frequency tuning device based on silicon based composite optical waveguide will be explored. The depth suppression technology of phase noise will be investigated to realize low noise single frequency fiber lasers with a frequency bandwidth of less than 100 Hz and wavelength tuning accuracy of ~100 MHz, achieving single or multiple wavelength fine and wide spectrum independent and stable tuning. The innovations consist of: I. It is proposed that the laser linewidth deep compression of arbitrary wave band is realized by the integration of all fiber whispering gallery cavity feedback Rayleigh scattering. II. The wavelength precision tuning based on the new material and the micro ring structure is proposed. III. It is proposed that the depth suppression technology of phase noise by combining the optoelectrical feedback and the optical feedback. It’s anticipated that our low noise tunable single frequency fiber laser has broad application prospects in many fields such as optical communication and sensing and so on.

窄线宽光纤激光器具有单色性好、时间相干性高、相位噪声低等突出优点，已成为光通信和传感领域不可或缺的激光光源。本项目针对大容量长距离相干光通信、超长距离光纤传感以及微波光子学等方面的研究对光纤激光器的线宽深压缩、波长精密调谐以及噪声高效抑制的迫切需求，以瑞利散射压缩激光线宽作突破口，研究具有高瑞利散射系数的高增益光纤，探索基于二维材料和在纤微腔瑞利反馈滤波器，以及基于硅基复合光波导的微环频率调谐器件，针对性的研究相位噪声抑制技术，从而实现对单/多个波长进行精细、宽光谱独立稳定调谐的低噪声单频光纤激光器，指标达到线宽低于100赫兹、波长调谐精度约100兆赫兹。项目创新在于：提出全光纤微腔反馈瑞利散射实现任意波段激光的线宽深压缩、提出新材料和微环结构实现波长的精密调谐、提出结合光电反馈和光学反馈的相位噪声高效抑制方法。预期研制的低噪声可调谐单频光纤激光器在多个领域具有广阔的应用前景。

为解决常态条件下单纵模激光器线宽难以深压缩的瓶颈问题，本项目提出了激光频域线宽深度压缩的新机制和激光新架构，研制了可实现激光线宽深度压缩、波长精密调谐和噪声抑制的多种功能器件，开发了超窄线宽激光器线宽及噪声测试仪，实现了波长可精密调谐的超窄线宽激光输出及其时频特性的实时表征。基于瑞利散射的频域演变特征，本项目利用主腔结合分布反馈外腔构建了自适应反馈激光新架构并从经典和量子两个角度揭示了瑞利散射反馈下激光频域演变特征。在常态条件下，采用一维波导中累积的瑞利散射将光纤激光器和半导体激光器的线宽分别压缩至100Hz和10Hz量级。利用石墨烯的相干全光调制效应研制了多种波长精密调谐器件，包括光纤光栅、马赫-贞德干涉仪和高品质因子谐振腔等，在保持超窄线宽输出的前提下达到了精度优于1MHz的调谐水平。基于能量上转换效应的理论分析和半导体光放大器噪声抑制等技术，将超窄线宽激光器的相位噪声降低至-135dBc/Hz-1m@10kHz，相对强度噪声在100kHz-50MHz范围内降至-155dB/Hz。采用短光纤延迟自外差和相关包络谱探测法搭建的超窄线宽激光器线宽及噪声测量仪实现了对百赫兹甚至赫兹量级激光线宽精确测量及其时频特性的实时监测。本项目研制的可调谐超窄线宽光纤激光器可为相干光通信、调频连续波激光雷达以及分布式传感等提供核心光源。课题组已将其用于分布式光纤传感系统，并成功实现储油罐和炼钢炉健康监测以及航天器件的实时精密测量。除此之外，本项目提出的基于自适应外腔反馈的激光新构架对增益类型的激光器具有普适性，为拓展窄线宽激光器的应用领域和提高基于窄线宽激光器的通信与测量等系统的性能提供一种普适有效的解决方案。