用于产生微波以及单频THz辐射源的低噪声双频光纤激光器研究

With the development of 5G microwave communication, photon microwave radar, terahertz cancer detection and other cutting-edge applications. The research of new microwave source based on microwave photonics and single frequency terahertz source becomes a hot spot. Among them, by virtue of the advantages of simple structure and high integration degree, high quality microwave and terahertz single frequency radiation through optical difference frequency has been widely concerned. This application project mainly studies dual-frequency fiber laser with hundred GHz frequency difference, and the design and production of its core components are completed independently. In addition to the advantages of the single-frequency fiber laser, the two frequency longitudinal modes have the advantages of high coherence and low phase noise. The spectrum is broadened through the nonlinear effect of fiber, and the comb spectrum with low phase noise with the same hundred GHz interval is generated. With the help of the most advanced technologies at present, such as optical microcavity, metasurface and metamaterials, the single frequency signal of high quality is generated by optical difference frequency, and the spectrum ranges from microwave to terahertz. Compared with the difference frequency generated by two independent single-frequency lasers, this scheme has the advantages of simple overall structure, high integration and no need for complex phase locking, etc. The research results will be of great value in promoting the application of microwave photonics, single-frequency terahertz and other technologies in frontier fields.

随着5G微波通信，光子微波雷达，太赫兹癌症检测等前沿应用领域的发展。基于微波光子学技术的新型微波源和单频太赫兹源的研究成为热点。其中, 凭借结构简单，集成度高等优势，通过光学差频产生高品质微波及太赫兹单频辐射的技术途径得到广泛关注。本申请项目主要研究具有百GHz频差的双频光纤激光器，其核心元器件的设计和制作均为自主完成。该双频激光器除了具备单频光纤激光器诸多优势之外，其两个频率纵模还具备高相干性，低相位噪声等优点。通过光纤非线性效应实现光谱展宽，产生同样具有百GHz间隔的低相位噪声梳状光谱，借助光学微腔，超表面，超材料等目前最先进技术，通过光学差频的方式产生高品质的单频信号，频谱范围覆盖从微波到太赫兹。相较于两台独立单频激光器产生差频的方式，该方案具有整体结构简单，集成度高，无需复杂的相位锁定等优点，研究成果对于推动微波光子学，单频太赫兹等技术在前沿领域的应用将产生十分重要的价值。

在本项目的支持下，我们开展了优化光纤光栅刻写系统，刻写低损耗光纤光栅，低噪声单频以及双频光纤激光器搭建以及利用四波混频效应产生梳状光谱等工作。目前实现了1μm，1.5μm以及2μm波段的单波长和双波长低损耗光纤光栅，双波长光纤光栅的波长间隔均大于百GHz。利用我们自主研制的光纤光栅我们实现了不同波段的高性能单频光纤激光器，我们还与国内外知名研究团队合作，将这些激光器应用于西澳大利亚大学的新一代引力波探测系统，以及清华大学谈宜东团队的高灵敏度测距系统中，这些应用成功验证了我们研发的激光器性能。针对双频光纤激光器我们采用1046nm/1060nm双频光纤激光器，其对应的频差在3.7THz左右。利用高非线性光纤中的四波混频效应，我们成功实现了梳状光谱的产生，在峰值功率13W实现了20dB范围内产生46条新光谱，3dB范围内的光谱宽度大于1THz，光谱信噪比达到了35dB。通过选择相应的波长，可以实现双频频差的调谐，这一成果对于下一步产生可调谐单频THz辐射源将至关重要。其中相关技术与西澳大利亚大学签署一项12万澳币的合同，用于为其研发一套高功率低噪声的2μm单频光纤激光器。利用我们搭建的光纤光栅刻写平台，我们与北京镭科光电科技有限公司开展合作，为其制备高性能的光纤光栅，合同总价值25万元。项目研究成果发表SCI、EI论文6篇，其中2篇文章为特邀文章。项目申请人以及团队相关人员受邀做邀请报告4次，培养硕士研究生4人。相关成果将进一步推动低噪声单频以及双频光纤激光器在精密探测领域中的应用研究。