超短明暗“孤子对”光纤激光器基本物理及关键技术问题研究

Soliton is a stable localized nonlinear wave that has been observed in many nonlinear systems. Optical solitons have been observed in fiber lasers. However, compared with other nonlinear systems where solitons were observed, a fiber laser has the characteristics that i) it has a simple configuration; ii) its operation condition can be easily controlled and precisely measured. Hence, fiber lasers have been found to be an ideal testbed for the nonlinear soliton dynamics study. Not only stable parameter-controlable bright solitons but also the dark solitons were experimentally observed in fiber lasers. Nevertheless, it is challenge to generate stable dark soliton emission from a fiber laser due to that the dark soliton generation is threshold-less.In this project we propose a novel technique for the generation of stable ultrashort brigh-dark soliton pairs in a fiber laser. We show that under the mutual action of the nonlinear light propagation in fibers, the nonlinear coupling between the two orthogonal polarization states of light in a weakly birefringent fiber, and the feedback resulted from the laser cavity, stable bright-dark vector solitons can be generated in a fiber laser. And through the coupling between the bright-dark solitons,stable ultra-short dark pulses with controllable parameters can be further realized by controlling the bright soliton. Under appropriate conditions, the black-white vector soliton generation is also expected. In addition, the generation of bright-dark soliton pairs and the black-white soliton pairs in fiber lasers at different wavelengths will also be investigated, and their optimum operation conditions will be determined. Reliable laser sources that can emit stable dark solitons will be developed for the fiber telecommunication systems application purpose and for the dark solitons-matter interaction studies

孤子现象广泛存在于各种非线性系统中。与其它孤子非线性系统相比，光纤激光器结构较为简单，系统参数相对容易控制，因此是孤子非线性动力学研究的理想对象。光纤激光器中可产生稳定的参数可控的亮孤子，暗孤子虽然也存在于光纤激光器中，但难以实现稳定的暗孤子输出。本项目中将通过有机合理地组合光在光纤中的非线性传输效应，光偏振态之间的非线性耦合效应，以及激光腔的反馈效应，在激光器中产生稳定的明-暗孤子对输出，并通过控制亮孤子来实现参数可控的稳定超短暗孤子输出。在一定条件下实现激光器的黑白孤子对输出。并进一步从实验上研究不同波长光纤激光器中明暗孤子对，黑白孤子对的形成及特性,归纳总结出实现明暗孤子激光振荡的最佳激光器参数条件，构建不同波长明暗孤子输出的光纤激光器。为实现基于暗孤子的光纤通信系统以及研究暗孤子与物质的相互作用提供可靠的激光源。

孤子现象广泛存在于自然界各种非线性系统中. 关于各种孤子波的形成及特性的研究是自然科学研究的一个重要领域。光在单模光纤中非线性传输所产生的光孤子由于其理论的重要性和在光通信及光信号处理领域的潜在应用价值, 也一直受到人们极大的关注和重点研究. 该项目利用特殊设计的单模光纤激光器作为实验平台, 利用在一定条件下光在光纤激光器腔中传输的特性与在无穷长光纤中等价的性质, 对在不同参数条件下单模光纤中形成的光孤子进行了深入系统的理论及实验研究。在该研究中我们首次从实验上证实了弱双折射光纤中垂直偏振态间共振耦合所形成的黑-白矢量孤子, 非共振耦合作用下所形成的明-暗孤子, 矢量暗孤子, 以及光纤中三阶色散所支持的矢量明-暗孤子, 矢量明-反暗孤子, 并对他们的特性进行了分析研究. 同时我们还对腔中存在的增益效应, 增益带宽限制等效应对所形成的孤子特性的影响进行了理论及实验研究, 提出了耗散明-暗矢量孤子, 耗散Peregrine 孤子等概念. 通过对非共振腔情况的理论研究, 我们首先提出了激光器中的腔感应调致不稳定, 并从实验上证实了其存在. 此外, 我们还对铥光纤激光器中的一些特殊光孤子现象, 以及二极管泵浦的固体激光器中的光孤子进行了研究. 我们的研究结果极大地丰富了孤子理论以及人们对非线性系统特性的认识. 部分研究结果还对高重率脉冲序列的产生, 超短脉冲的产生有直接的指导作用.