相对论涡旋高次谐波的产生与调控理论研究

目前，具有螺旋相位波前和环状光强分布的涡旋光束已在光学领域获得了广泛应用，其产生与调控自然成了研究的热点。利用三维粒子模拟程序对双色拉盖尔高斯激光驱动固体等离子激发同时携带自旋角动量与轨道角动量的高次谐波的物理过程进行了研究，根据高次谐波产生过程中的光子能量与角动量守恒定律对其内在物理机制进行了理论分析，并讨论了对谐波阶次、偏振态（自旋角动量）以及拓扑荷数（轨道角动量）进行调控的方法。研究结果为开发高亮度、超短超快、短波长、自旋与轨道角动量可调控的涡旋光束辐射源提供了理论依据，在光学微操控、超分辨成像、光通信以及离子加速等领域具有较大的实际应用前景。

Theoretical investigation of relativistic vortex high-order harmonics generation and manipulation

Vortex beams with ultra-high brilliance can greatly enrich the light and matter interaction process and even shed light on the unexpected information in relativistic nonlinear optics. Thus, we propose a scheme for relativistic intense vortex harmonic radiation by use of bi-circular Laguerre-Gaussian lasers irradiating relativistic plasmas. According to the law of conservation of photon energy and angular momentum during the generation of higher-order harmonics, the emitted harmonics own controllable spin and orbital angular momentum simultaneously, as the three-dimensional particle-in-cell simulation results shown. Based on this discussion, the methods of adjusting harmonic order, polarization state (spin angular momentum) and topological charge number (orbital angular momentum) are proposed. It is found that if frequency ratio and circular polarization state of the bi-chromatic Laguerre-Gaussian laser are changed, such as with the same right-handed or left-handed circular polarization. The harmonic characteristics, including the harmonic order, the polarization state and the vortex order are flexibly controlled. Therefore, this work provides an efficient and practical approach to produce bright, spectral tunable harmonic radiation with designable spin and orbital angular momentum, which may own the application prospect going from optical communications, bio-photonics, optical micromanipulations to ion accelerations.