涡旋飞秒脉冲成丝及其奇异结构演化的理论研究

Research on nonlinear propagation of femtosecond vortex pulses is very important not only to the fundamental physics but also to the related fields and applications such as astronomical observation, laser material processing and optical communication. The nonlinear propagation of the femtosecond vortex pulse is special because the ultrashort pulse has a helical phase-front and phase singularity. However, many important processes are unclear and need to be investigated during the nonlinear propagation of femtosecond vortex pulse, such as the mechanism and the control of the filamentation, the evolution and transfer of the singular structures of phase and intensity. In this project, we propose to theoretically study the nonlinear propagation of femtosecond vortex pulse in fused silica. We will investigate the filamentation mechanism and the evolution of singular structure by simulating the spatio-temporal evolution of femtosecond vortex pulse. The control of filamentation and supercontinuum will also be investigated. The condition and mechanism of supercontinuum and third-harmonic generation with singular structure will be obtained. The implementation of this project will provide new ways to control filamentation and generate new types of femtosecond vortex pulse, and promote the related applications in the field of strong field physics.

涡旋飞秒脉冲的非线性传输研究不仅是重要的基础物理问题，也是天文观测，激光微纳加工和光通信等很多交叉学科和应用领域的重要理论和技术基础。涡旋飞秒脉冲兼具相位光强奇异结构和超快超强特性，具有独特的时空螺旋传输特性，国际上对其中很多基础物理问题的研究还十分欠缺，尤其是涡旋脉冲成丝的时空演化以及优化控制的物理机制，奇异结构的保持和传递等方面尚无系统研究。本项目拟开展涡旋飞秒脉冲在熔融石英中的非线性传输理论研究，通过数值模拟涡旋飞秒脉冲成丝的时空演化过程，揭示相位和光强奇异结构的演化规律以及成丝物理机制，对成丝过程和超连续辐射进行优化控制，并获得具有涡旋奇异结构的超连续辐射和三次谐波的产生条件和机制。本项目的实施，将填补国际上在该领域的研究空白，为飞秒激光的成丝控制和产生新的涡旋飞秒脉冲提供新方法，推动涡旋飞秒脉冲的强场物理应用。

飞秒涡旋激光兼具涡旋光场的奇异结构和飞秒脉冲的超快超强特性，能够为强场物理研究提供独特的光源。对飞秒涡旋激光非线性传输过程的研究，可以为飞秒脉冲成丝控制提供理论基础，并为产生新的涡旋飞秒脉冲提供物理基础和方法，推动涡旋飞秒脉冲的强场物理应用。基于此，本项目对飞秒涡旋激光非线性成丝的时空演化过程进行模拟，对此过程中的涡旋圆环形强度分布和螺旋相位分布的演化规律及机制进行了研究。通过本项目的开展，获得了透镜阵列聚焦下的涡旋飞秒脉冲环形成丝阵列，通过改变聚焦条件和拓扑荷实现细丝旋转速率的控制，并通过密度孔的引入延长了成丝长度。通过对飞秒涡旋激光在玻璃薄片中非线性传输过程的研究，获得了产生高功率涡旋超连续辐射和少周期涡旋激光的机制。此外，也获得了飞秒涡旋激光产生具有涡旋结构的三次谐波的条件和物理机制。本项目的完成为飞秒激光成丝控制和产生新的涡旋飞秒激光提供了理论基础和新方法。