Temporal Focusing Enables Distortion-Resistant high-intensity Spatiotemporal Optical Vortices

TL;DR

This paper introduces a novel spectral phase modulation technique in temporal focusing to generate stable, distortion-resistant high-intensity spatiotemporal optical vortices with controllable angular momentum, suitable for high-resolution applications.

Contribution

The authors develop a spectral phase modulation method that enables stable, distortion-free STOVs with adjustable angular momentum in high-NA focusing setups.

Findings

Stable STOVs with self-similar evolution over extended focus

Continuous steering of orbital angular momentum vector

Compatibility with high-NA focusing for high-intensity applications

Abstract

Spatiotemporal optical vortices (STOVs) carry transverse orbital angular momentum and offer new degrees of freedom for light-matter interactions. Yet conventional focusing of STOVs introduces spatiotemporal astigmatism: the beam diffracts while the pulse duration stays constant, causing the vortex to deform away from focus. Here we overcome this limitation by introducing spectral phase modulation into a temporal focusing configuration, where angular dispersion forces the pulse to compress only at the geometric focus so that the spatial and temporal dimensions focus and defocus together. Our approach generates stable STOVs with self-similar, distortion-free evolution over an extended focal region. Besides, the orbital angular momentum vector can be continuously steered from purely longitudinal to strongly tilted orientations by adjusting the spatial dispersion, objective focal length, or input beam size. More importantly, our method offers full compatibility with high NA focusing geometry, allowing high-intensity and high-resolution applications. We validate these properties through femtosecond laser ablation under high-NA conditions and interferometric spatiotemporal field reconstruction under low-NA conditions.