高次谐波时空光学涡旋的可控产生
Controlled generation of high-harmonic spatiotemporal optical vortices
AI总结：
本文通过高次谐波产生技术，将定制脉冲整形器产生的红外时空光学涡旋脉冲上转换至极紫外频段，明确其拓扑电荷规律并实现可控产生，为相关光谱学研究提供新工具。
AI中文摘要：
时空光学涡旋（STOV）脉冲是一类奇特的光态，尽管具有拓扑电荷，但其横向轨道角动量仍存在争议。此前相关研究均在常规光学波长下开展，本文通过高次谐波产生（HHG）技术，首次将这类STOV脉冲上转换至极紫外（XUV）频段。我们采用定制脉冲整形器产生拓扑电荷ℓ=±1和±2的圆对称红外STOV脉冲，将其聚焦于氩气中以驱动谐波产生，各阶次谐波q在远场形成空间光谱环。这些环的半径对q和ℓ的依赖关系表明，XUV涡旋的电荷满足ℓ_q = q×ℓ，且这些模式对聚焦位置的敏感性进一步确立了对其产生的可控性。XUV STOV的可用性为研究其难以捉摸的角动量在光电离及其他超快光谱学中的应用开辟了新途径。
英文摘要：
Spatiotemporal optical vortex (STOV) pulses are puzzling states of light, which see their transverse orbital angular momentum being debated in spite of possessing a topological charge. Thus far studied at conventional optical wavelengths, we herein demonstrate their upconversion to extreme ultraviolet (XUV) frequencies via high-harmonic generation (HHG). Circularly-symmetric infrared STOV pulses of topological charges $\ell=\pm1$ and $\pm2$ from a bespoke pulse shaper are focused in argon to drive harmonics, each order $q$ forming a spatiospectral ring in the far-field. Dependence of their radii on $q$ and $\ell$ indicates XUV vortices of charge ${\ell}_{q} = q \times \ell$, and sensitivity of these modes to the focus position further establishes control over their production. The availability of XUV STOVs unlocks investigations and applications of their elusive angular momentum in the context of photoionization and other ultrafast spectroscopies.
