三波谐振介质中光学异常波的共存及其实验观测

Because of their mysterious and potentially devastating manifestations, oceanic rogue waves have been the focus of intense research for more than a decade. The rogue wave terminology itself refers to the adverse surprise that is experienced when a transient giant wave of extreme amplitude or steepness is suddenly formed in the vicinity of a cruising ship. Recently, rogue wave research was also spreading widely to other physical disciplines that share general features of nonlinearity and complexity. These new avenues for rogue wave research include fluid dynamics, nonlinear optics, plasma physics, and Bose-Einstein condensation. Particularly, in nonlinear optics, optical rogue waves have become one of the most active topics on the cutting edge of fundamental soliton research, and have been confirmed experimentally in optical fibers, mode-locked lasers, and femtosecond filamentation. Despite all this, however, the possibility to accede to a general understanding of the origin of rogue waves is still an open question, and some novel rogue wave dynamics such as dark rogue waves and coexisting rogue waves is still not observed yet. In this project, we commit ourselves to explore the coexistence of optical rogue waves in three-wave resonant media both theoretically and experimentally. Specifically, we first derive the exact rogue wave solutions of the three-wave resonant equations, including the 3-component long wave-short wave (3C LWSW) equations and the three-wave resonant interaction (TWRI) equations, based on either the Darboux transformation or the Hirota bilinear method, and discuss their complex dynamics as well as the underlying physics. Then, we perform extensive numerical simulations to confirm the robustness of the involved dynamics, using the multiphysics simulation software or the split-step Fourier method. Lastly, we set up a self-consistent three-wave resonant optical system and use it to observe the formation of a dark rogue wave and the coexistence of different rogue waves. We expect that these studies may help to clarify some disputable issues in current rogue wave research and thus enrich our understanding on the nature of rogue waves.

由于其神秘莫测和潜在破坏性，海洋异常波(rogue waves)一直是过去十多年来的研究焦点。最近，异常波研究已延伸至物理学的其他学科，如流体动力学、非线性光学、等离子体物理、波色爱因斯坦凝聚等。特别在非线性光学领域，光学异常波已成为当前最为前沿的研究话题之一，并相继在光纤、锁模激光器、和飞秒成丝中得到实验证实。尽管如此，但科学界对异常波根源的理解还在争论中，一些新颖的动力学如暗异常波、异常波共存等还未得到实验验证。本项目将致力于理论和实验研究三波谐振光学介质中不同异常波态的形成与共存现象，其内容包括：寻求三波谐振方程（3C LWSW/TWRI方程）的精确异常波解，讨论异常波的产生机制与复杂动力学；数值模拟异常波的典型动力学及其坚固性；建立与模型方程自洽的三波谐振光学系统，实验观测暗异常波产生及异常波的共存现象。我们预期这些研究将有助于澄清异常波现有的学术争议，加深人们对其本质特征的理解。

异常波（rogue waves）术语最初用于描述深海上发生的一类臭名昭著且神秘的极端稀有海浪事件，俗称疯狗浪，其常被认为是无数海难事故的罪魁祸首。它们掀起的滔天巨浪像堵水墙一样，不期而至出现在某处，然后消失得无影无踪。作为深海里的“怪兽”，异常波一直以航海传说流传几百年了，直到最近半个世纪以来才被科学家们证实是真实存在的，且经常发生。现在，异常波已经成为目前最活跃的研究话题之一，研究范围遍及海洋学、流体动力学、光学、等离子体物理、波色爱因斯坦凝聚、甚至金融学等领域。特别在光学领域，随着可靠激光源的普及使用以及实时检测技术的成熟，人们已在许多物理设置（如光纤、锁模激光器、和光学湍流）中成功观测到海洋疯狗浪的光学类似物，即光学异常波。然而，尽管上述各类研究如火如荼，但异常波的基本来源依然不清晰，许多异常波的新颖动力学还未得到深入理解。..在本项目中，我们借助达布变换、调制不稳定性分析、和广泛的数值模拟，系统深入地研究了标量、矢量、多维非线性系统中的复杂异常波现象，揭示了许多新颖的异常波动力学及其潜在物理思想。例如，我们首次报道了矢量暗“三姊妹”异常波、共存异常波、表指针型异常波、互补型异常波、异常波光子弹、啁啾Peregrine孤子、和反常Peregrine孤子等，数值验证了其强稳定性并预测了其实验可行性。在实验上，我们首次在长程通信光纤上观测到了本课题组2014年所预测的矢量暗“三姊妹”异常波现象。此外，我们也实验研究了氮气分子在强近红外飞秒激光脉冲照射下所发生的无腔超辐射现象。所有这些研究成果已整理成17篇论文发表在国外权威期刊（如Physical Review Letters）上，至今已引用超300次。特别地，我们2015年发表的一篇JPA论文被IOP授予“2018中国作者高被引论文奖”，该奖项主要针对2015-2017年发表在IOP期刊上的前1%高被引论文。此外，我们还为2017年出版的IOP专著《Nonlinear Guided Wave Optics》编写章节1篇。可以预见，这些研究成果将对光学（或其他相关学科）极端波事件的深入理解和预测具有重要的理论意义和实际价值。