轴对称矢量光束超短脉冲产生及其传输放大特性研究

Cylindrical vector beams (CVBs) have potential applications in the area of laser manufacturing, surface plasmon excitation, particle trapping and etc, most of these applications are limited by the beam spectrum width and peak power. At present, the CVB generation in fiber lasers mostly use few mode fiber Bragg gratings (FM-FBG) as the transversal mode excitation and selection element. In this scheme, the laser spectrum are restricted to the operation bandwidth of the FM-FBG so that it is difficult to realize CVB generation either within wide spectrum or with ultra-fast pulse. To expand the applications, the objective of this project is to take deep research on the polarization manipulation and mode coupling within wide spectrum in fiber lasers and realize CVB generation within wide spectrum, especially CVB pulse generation with the duration of femoseconds. Further theorical and experimental research on the nonlinear effect and the mode distortion during the CVB transmission and amplification will be achieved based on the generated CVB pulse.

轴对称矢量光束在激光加工，表面等离子体激发，粒子操控等领域有着极高的应用前景，其中大部分应用都需要较宽的激光谱宽和较高的峰值功率。目前光纤激光器中的轴对称矢量光束产生大都采用少模光纤光栅作为横模激励和选择元件，此类方案中激光器谐振光谱被局限在少模光纤光栅的运转光谱范围内，从而很难实现轴对称矢量光束的宽光谱和超短脉冲产生。为拓展其应用前景，本项目拟对光纤激光器中宽光谱范围内偏振调控和模式耦合机理深入研究进而实现宽光谱轴对称矢量光束产生，尤其实现飞秒量级的轴对称矢量光束超短脉冲输出。在产生的超短脉冲基础上，进一步从理论和实验上研究轴对称矢量光束超短脉冲在传输放大过程中的非线性效应和模式畸变。

轴对称矢量光束在激光加工，表面等离子体激发，粒子操控等领域有着极高的应用前景， 其中大部分应用都需要较宽的激光谱宽和较高的峰值功率。为拓展其应用前景，本项目对光纤激光器中宽光谱范围内偏振调控和模式耦合机理深入研究，利用单模光纤和少模光纤熔融拉锥的方式，实现了光纤中的轴对称矢量光束的直接耦合输出，并基于少模光纤-渐变折射率光纤-少模光纤结构实现了腔内高阶模式的低损耗耦合产生。在2微米波段，基于各类可饱和吸收体实现了从基频到高次谐波的被动锁模脉冲输出，并从实验和数值模拟上研究了腔内耗散孤子形成的动态过程，为后续中红外波段的高功率轴对称矢量光束产生提供理论指导。基于空芯光子晶体光纤结构设计实现了各简并高阶模式间的有效折射率差异增大，利用该光纤可以在近红外和中红外波段实现高阶模式和相位涡旋光束的稳定传输放大。此外，为研究轴对称矢量光束的高功率放大过程中的非线性效应，基于非线性薛定谔方程和光束传播算法，成功构建了高阶模式在光纤中的各类非线性效应理论模型，并完成相关数值模拟。