光纤激光器"类噪声"脉冲动力学特性研究

The state of noise-like pulses is a special mode locking state in ultrafast fiber lasers. The pulse duration of a noise-like pulse could be at the range from picosecond to nanosecond, while the noise-like pulses have internal structure with femtosecond duration. Noise-like pulses are not transform-limited. The project will focus on the nonlinear dynamics of noise-like pulse generation in fiber lasers to avoid the conflict between the ceaseless demands for higher pulse energy and the possibly destroy of the transform-limited feature of ultrashort pulses generated from a fiber laser. A fiber laser made of components of polarization-maintained fibers will be built. The nonlinear optical loop mirror will be used to achieve the generation of noise-like pulses in the all-polarization-maintained fiber laser. High nonlinear fiber will be adopted in a long-cavity fiber laser to see how to achieve noise-like pulses with larger pulse energy and broader bandwidth. Super-continuum generation will be tested using the amplified noise-like pulses and the physical mechanism will be explored. We would take the fiber lasers as a platform for the study of nonlinear dissipative dynamic systems. The non-deterministic feature of the fiber laser operation based on noise-like pulse generation will be studied to better understand the dynamic characteristics of the mode-locking fiber lasers. We believe that, based on the deeper insight of the properties of noise-like pulses and the physical mechanism for the noise-like pulse generation, the technique we develop in this project will help to broaden the exploitation of the fiber lasers that can generate noise-like pulses, which is current lagged behind the fiber lasers that can generate stable mode-locking pulses.

“类噪声”脉冲是超快光纤激光器中产生的一种特殊状态，时域上存在两种时间尺度：飞秒脉宽内部结构和皮秒/纳秒量级脉冲宽度。“类噪声”脉冲不具有变换极限特性。本项目针对超快光纤激光难以兼顾对脉冲能量提高的持续性要求和保持变换极限特性的问题，提出和研究光纤激光器中产生“类噪声”脉冲的动力学过程。采用全保偏结构并使用非线性环形镜锁模技术实现不受环境干扰的“类噪声”脉冲光纤激光器；在光纤激光器中引入高非线性光纤并采用长腔，探讨获得大能量、宽带“类噪声”脉冲的条件；使用“类噪声”脉冲实现超连续谱输出，研究其形成机理。本课题将发展利用光纤锁模激光器研究非线性耗散动力学系统的平台，揭示光纤激光器的非稳定锁模特征，为更好的理解锁模光纤激光器动力学特性奠定理论和实验基础。通过本项目对“类噪声”脉冲的性质和形成机理的深入研究，以期对其有一突破性的认识从而使对“类噪声”脉冲的利用可以赶上现有的稳定锁模脉冲。

本项目针对超快光纤激光难以兼顾对脉冲能量提高的持续性要求和保持变换极限特性的问题，提出和研究光纤激光器中产生“类噪声”脉冲的动力学过程。探讨获得大能量、宽带“类噪声”脉冲的条件。发展利用光纤锁模激光器研究非线性耗散动力学系统的平台，揭示光纤激光器的非稳定锁模特征，为更好的理解锁模光纤激光器动力学特性奠定理论和实验基础。在基金支持下，研究内容包括对超快光纤激光器中产生具有更大脉冲能量的超短脉冲的研究历史进行了回顾和总结；综述类噪声脉冲光纤激光器的国内外研究现状；实现谱宽为203nm的类噪声脉冲，是目前已实现的具有最宽带宽的类噪声脉冲；发现h形状脉冲的存在，实现脉冲占空比为98.2%的h脉冲, 是目前光纤激光器中报道的最大值；证明了基于单层石墨烯与瞬逝场相互作用所产生的弱偏振相关性的锁模可行性；受邀对超快光纤激光器中的周期分岔研究进展做综述；证明在掺钬光纤激光器中同样存在耗散孤子共振锁模；与天津大学胡明列教授课题组合作，提出了一种时域孤子分子动力学探测的新方法，该方法将时域孤子分子动力学的测量分辨率提升至数十阿秒量级，有望开辟孤子间弱相互作用的基础理论和实验研究的新领域；通过合成来自于群速度锁定矢量耗散孤子的垂直偏振分量的投影，实现高阶矢量孤子结构；报道了在铥钬共掺光纤激光器中存在的一种被动调Q的峰值功率限制效应；报道了掺铥光纤激光器中环境敏感的窄带宽h型脉冲的产生和演变；报道了工作在大的正常色散区的掺钬光纤激光器中产生的耗散孤子共振脉冲以及其演变为爆发的脉冲集群的过程；综述了光纤系统中各种孤子分子的产生和传播；在超长腔掺铥光纤激光器中实验证实了一类可调节可转换的谐波锁模h型脉冲产生；观察到耗散孤子共振型脉冲的脉冲分裂现象以及耗散孤子共振型脉冲的脉宽压窄现象；报道了在具有反常色散的被动锁模光纤激光器中产生类噪声脉冲的解析解，确定了单孤子和类噪声脉冲之间的竞争机制。