宽带、低相噪光学频率梳的产生机理及实验研究

Optical frequency comb (OFC) has attracted more and more interests due to its massive applications in high precision measurement, ultra dense wavelength division multiplexing, optical arbitrary waveform generation, chemical detection and other fields. In these applications, OFCs are required to be not only with large bandwidth, but also with high stability, i.e. low phase noise. In this project, a broadband OFC generator will be designed based on electro-optical modulation and optical parametric process. Through theoretical analysis, numerical modeling and simulation, the evolution mechanism of the phase noise in the laser and radio-frequency (RF) signal in the electro-optical modulation and optical parametric process will be investigated to find the phase noise distribution pattern of generated OFC spectral lines. And an effective scheme for reducing the phase noise will be proposed. Based on the theoretical results, an experimental platform to generate OFC with broad bandwidth and low phase noise will be established. Through our experiments, OFCs with spectral line interval at 10 GHz, flatness of 3dB bandwidth more than 10 THz and spectral line-width below 100 kHz will be generated. The anticipated achievements can provide theoretical fundaments for the design of OFC generator with large bandwidth and high stability, and the results can provide reference scheme for its implementation and application. Meanwhile, it is of important science value for promoting the research level of our country in the field of microwave photonics.

光学频率梳（简称光频梳，OFC），由于其在高精度测量、超密集波分复用传输、全光任意波产生及化学探测等领域具有很大的应用前景，而受到越来越多的关注。在这些应用中，不仅要求光频梳具有大的带宽，更要有高的稳定性，即具有尽可能低的相位噪声。本项目基于电光调制与光参量过程设计宽带OFC发生器，通过理论分析及数值建模与仿真，研究激光器和射频（RF）调制信号相位噪声在电光调制及光参量过程中的演变机理，揭示所生成光频梳谱线相位噪声的分布规律，提出可降低相位噪声的有效方案。在此基础上，建立产生宽带、低相噪光频梳的实验平台，通过实验生成谱线间隔是10GHz，平坦度小于3dB时带宽达10THz以上，且谱线线宽都低于100kHz的光频梳。预期成果可为大带宽、高稳定性光频梳发生器的设计奠定理论基础，并为其实现与应用提供参考方案。同时，对提升我国在微波光子学领域的研究水平具有重要的科学价值。

本项目围绕宽带、低相噪光频梳的产生展开理论及实验研究，建立了基于高非线性光纤（HNLF）产生宽带参量光频梳的系统理论模型，探究了激光器和RF信号相位噪声，放大器噪声在光参量过程中的演化及相互作用规律，揭示了光参量混频过程中，调制不稳定性对所生成光频梳性能影响的规律。在此基础上，重点研究了利用光注入锁定和光电振荡器降低光频梳谱线相位噪声的方案，设计实现了一种基于光频移器和注入锁定的参量光频梳发生器，实验产生了谱线间隔为10GHz、包含38条谱线的光频梳；设计并实现了一种基于受激布里渊散射（SBS）的自振荡光频梳发生器，获得了平坦度为3dB，谱线间隔等于光纤布里渊频移，包含9条谱线的光频梳；设计并实现了一种基于HNLF的参量振荡器，产生了谱线间隔为HNLF二倍布里渊频移的可调谐参量光频梳；设计实现了一种基于电致吸收调制激光器（EML）的自振荡光频梳发生器，实验产生了具有不同包络特征的光频梳；设计实现了两种基于EML的自振荡参量光频梳发生器，实验分别产生了谱线间隔为10GHz和20GHz的低相噪的参量光频梳；设计实现了基于频移环路的宽带自振荡光频梳发生器，实验产生了谱线间隔为10GHz、平坦度为3dB、包含50条谱线的光频梳。以上研究成果为宽带、低相噪光频梳的产生提供了理论基础及实现参考方案。