Temporal Focusing Enables Distortion-Resistant High-Intensity Spatiotemporal Optical Vortices

Yet conventional focusing techniques for STOVs introduce spatiotemporal imbalance between spatial diffraction and temporal dispersion, which deforms the vortex away from the focal plane. Here we overcome this limitation by matching the temporal and spatial Rayleigh ranges through engineered angular dispersion, therefore enforcing self-similar spatiotemporal evolution.

This matching condition is implemented by incorporating spectral vortex phase modulation into a temporal focusing geometry, where angular dispersion compresses the pulse duration at the focus, enabling simultaneous focusing and defocusing of both spatial and temporal dimensions. The resulting STOVs preserve their ring-shaped intensity profile and helical phase singularity over an extended focal region. Besides, the orbital angular momentum vector of generated STOVs can be continuously steered from purely longitudinal to strongly tilted orientations by adjusting the spatial dispersion, objective focal length, or input beam size.