Four-dimensional light shaping: manipulating ultrafast spatio-temporal foci in space and time

TL;DR

This paper presents a novel method for shaping light in four dimensions by manipulating ultrafast spatio-temporal foci using phase-only holograms, enabling precise control in space and time for applications like microscopy and laser fabrication.

Contribution

It introduces a technique combining holography and spectral dispersion to generate 3D arrays of spatio-temporally focused spots with high axial confinement.

Findings

Successful generation of 3D spatio-temporal focal arrays

Enhanced axial confinement demonstrated in experiments

Applications in microscopy and laser fabrication

Abstract

Spectral dispersion of ultrashort pulses allows simultaneous focusing of light in both space and time creating so-called spatio-temporal foci. Such space-time coupling may be combined with existing holographic techniques to give a further dimension of control when generating focal light fields. It is shown that a phase-only hologram placed in the pupil plane of an objective and illuminated by a spatially chirped ultrashort pulse can be used to generate three dimensional arrays of spatio-temporally focused spots. Exploiting the pulse front tilt generated at focus when applying simultaneous spatial and temporal focusing (SSTF), it is possible to overlap neighbouring foci in time to create a smooth intensity distribution. The resulting light field displays a high level of axial confinement, with experimental demonstrations given through two-photon microscopy and non-linear laser fabrication of glass.