Diffraction-free space-time beams

TL;DR

This paper introduces a method to create diffraction-free, one-dimensional pulsed optical beams by exploiting spectral correlations between space and time, enabling self-similar propagation useful in microscopy and spectroscopy.

Contribution

The authors demonstrate a novel approach to synthesize one-dimensional diffraction-free beams using programmable spatio-temporal spectral correlations, expanding the capabilities of optical beam shaping.

Findings

Successfully generated axially invariant pulsed beams with tailored spectral correlations.

Demonstrated self-similar propagation of space-time beams in free space.

Potential applications in microscopy and nonlinear spectroscopy.

Abstract

Diffraction-free optical beams propagate freely without change in shape and scale. Monochromatic beams that avoid diffractive spreading require two-dimensional transverse profiles, and there are no corresponding solutions for profiles restricted to one transverse dimension. Here, we demonstrate that the temporal degree of freedom can be exploited to efficiently synthesize one-dimensional pulsed optical sheets that propagate self-similarly in free space. By introducing programmable conical (hyperbolic, parabolic, or elliptical) spectral correlations between the beam's spatio-temporal degrees of freedom, a continuum of families of axially invariant pulsed localized beams is generated. The spectral loci of such beams are the reduced-dimensionality trajectories at the intersection of the light-cone with spatio-temporal spectral planes. Far from being exceptional, self-similar axial propagation is a generic feature of fields whose spatial and temporal degrees of freedom are tightly correlated. These one-dimensional `space-time' beams can be useful in optical sheet microscopy, nonlinear spectroscopy, and non-contact measurements.