46 / 2026-03-20 16:30:05

High-harmonic Generation and Optical Torque Manipulation via Single-Slit Diffraction of Spatiotemporal Optical Vortices

Optical Torque,Spatiotemporal Vortex,High-harmonic Generation

极端条件下的基础物理 > 辐射与高能粒子产生

The interaction of spatiotemporal optical vortices (STOVs)—unique light pulses carrying transverse orbital angular momentum (OAM)—with plasma targets at relativistic intensities introduces new opportunities for manipulating light-matter interactions and angular momentum transport^[1-2]. In this work, we investigate the single-slit diffraction of a high-intensity STOV beam to demonstrate the transfer of transverse OAM to generated harmonics, and the manipulation of optical torque in the interaction.  Utilizing three-dimensional particle-in-cell (PIC) simulations and the relativistic oscillating window (ROW) analytical model^[3], we reveal how the spatiotemporal structure of the driver induces asymmetric electron dynamics at the diffraction screen, thereby exerting highly controllable torques on the plasma target.

Initially, we establish the diffraction dynamics when the slit is perpendicular to the OAM direction. When an STOV beam with a topological charge of  normally irradiates a solid plasma slit, the laser drives boundary electrons to oscillate at varying frequencies. This forms a "differential oscillating window" that inherently retains the driver's spatiotemporal phase structure. This differential oscillation efficiently transfers the transverse OAM to the diffracted light, producing high-harmonic STOV beams with topological charges that scale exactly as , where  is the harmonic order.

Building on this, we reveal that adjusting the slit direction relative to the driver's transverse OAM fundamentally alters the angular momentum exchange. When the slit is tilted, the inherently weaker intensity at the null core of the STOV pulse generates an asymmetric ponderomotive force along the slit. This asymmetry exerts a massive optical torque on the plasma, causing it to rotate and acquire substantial longitudinal angular momentum. To rigorously conserve total angular momentum, the plasma exerts an equal and opposite reactive torque on the electromagnetic wave. This physically rotates the generated harmonic beams so their transverse OAM aligns perpendicularly to the tilted slit. We demonstrate that the optical torque is maximized at an optimal intermediate tilt angle that depends on the slit width and the spatial scale of the STOV pulse. These findings provide a robust mechanism for manipulating extreme optical torques in relativistic plasmas^[4-5], paving the way for advanced STOV-based applications.



[1] L. Zhang, L. Ji, and B. Shen, Intense harmonic generation driven by a relativistic spatiotemporal vortex beam, High Pow. Laser Sci. Eng. 10, e46 (2022).

[2] F. Sun, W. Wang, H. Dong, J. He, Z. Shi, Z. Lv, Q. Zhan, Y. Leng, S. Zhuang, and R. Li, Generation of isolated attosecond electron sheet via relativistic spatiotemporal optical manipulation, Phys. Rev. Research 6, 013075 (2024).

[3] L. Yi, High-Harmonic Generation and Spin-Orbit Interaction of Light in a Relativistic Oscillating Window, Phys. Rev. Lett. 126, 134801 (2021).

[4] X. Xu, M. Nieto-Vesperinas, Y. Zhou, Y. Zhang, M. Li, F. J. Rodriguez-Fortuno, S. Yan, and B. Yao, Gradient and curl optical torques, Nat. Commun. 15, 6230 (2024).

[5] Y.-J. Wu, J.-H. Zhuang, P.-P. Yu, Y.-F. Liu, Z.-Q. Wang, Y.-M. Li, C.-W. Qiu, and L. Gong, Time-varying 3D optical torque via a single beam, Nat. Commun. 16, 593 (2025).