论文标题
自由空间中超快涡流传播的一般定律
General laws of the propagation of ultrafast vortices in free space
论文作者
论文摘要
我们对在自由空间中携带轨道角动量（OAM）的几个周期，超快涡旋（UFV）的传播进行了理论研究。我们的分析表明，时间动力学比几个循环基本的高斯光束更复杂，尤其是在接近单周期状态时，拓扑充电$ L $的幅度很高。最近描述的下限$ \ sqrt {| l |} $ to具有传播不变的时间形状的UFV的振荡次数（isodiffractracting ufvs）平均也可以保持通用类型的UFV，并且在该范围上方和下方的传播方向上，甚至在该边界上都有变化，甚至在该边界上都差异。这些变化取决于所谓的Porras因子或$ G_0 $ - 因子，以表征光谱成分雷利距离的依赖性。在给定的可用带宽下，UFV必须随着拓扑电荷的增加而暂时扩展，并且由于轴向变化，$ G_0 $依赖性下限在传播过程中必须扩大或可能在繁殖过程中缩小或可能缩小。 Under very restrictive conditions in their generation, an UFV can be shrunk below the lower bound $\sqrt{|l|}$ at a focus into a kind of locally compressed state of OAM, but it broadens well-above $\sqrt{|l|}$ and distorts in a tiny fraction of the depth of focus because of the dispersions introduced by Gouy's phase and wave front mismatch.这些传播现象具有含义，应在UFV的实验和应用中考虑，例如具有高OAM或基于OAM的Ultrafast通信系统以及其他物理学领域（例如声学或电子波）的实验和应用。
We conduct a theoretical study of the propagation of few-cycle, ultrafast vortices (UFVs) carrying orbital angular momentum (OAM) in free space. Our analysis reveals much more complex temporal dynamics than that of few-cycle fundamental Gaussian-like beams, particularly when approaching the single-cycle regime and the magnitude of the topological charge $l$ is high. The recently described lower bound $\sqrt{|l|}$ to the number of oscillations of UFVs with propagation-invariant temporal shape (isodiffracting UFVs) is found to hold on average also for UFVs of general type, with variations along the propagation direction above and below that bound, even vanishing locally. These variations are determined by the so-called Porras factor or $g_0$-factor characterizing the dependence of the Rayleigh distance of the spectral constituents with frequency. With a given available bandwidth, UFVs must widen temporally with increasing magnitude of the topological charge, and must widen or may shrink temporally during propagation as a result of the axially varying, $g_0$-dependent lower bound. Under very restrictive conditions in their generation, an UFV can be shrunk below the lower bound $\sqrt{|l|}$ at a focus into a kind of locally compressed state of OAM, but it broadens well-above $\sqrt{|l|}$ and distorts in a tiny fraction of the depth of focus because of the dispersions introduced by Gouy's phase and wave front mismatch. These propagation phenomena have implications and should be taken into account in experiments and applications of UFVs, such as the generation of high-harmonics and attosecond pulses with high OAM, or in OAM-based ultrafast communications systems, as well as in other areas of physics such as acoustics or electron waves.
