Space-time wave packets propagating a kilometer in air

TL;DR

This paper demonstrates diffraction-free space-time wave packets propagating over approximately one kilometer in open air, showing potential for long-distance laser applications with minimal spreading.

Contribution

It presents the first experimental demonstration of kilometer-scale propagation of space-time wave packets in open air and develops a theoretical model to understand and extend their propagation distance.

Findings

STWPs propagate approximately 1 km in open air with minimal diffraction.

Comparison shows STWPs maintain shape better than Gaussian beams over long distances.

A theoretical model identifies factors limiting propagation and suggests ways to extend it.

Abstract

We report on the diffraction-free propagation of space-time wave packets (STWPs) -- a class of propagation-invariant pulsed beams -- for $\sim\!1$ km in an open-air laser range in a low-turbulence scenario. Making use of $\approx\!100$-fs pulses (bandwidth $\sim\!25$ nm) at a wavelength of $\approx\!1$ $\mu$m, we construct an STWP with a transverse width of $\approx\!2$ mm that expands to $\approx\!3$ mm after $\sim\!500$ m, and another that expands from $\approx\!8$ mm to $\approx\!10$ mm after 1 km. The propagation of the STWPs is compared to Gaussian wave packets of the same transverse spatial width and bandwidth. We establish a theoretical model that accounts for the significant factors limiting the STWP propagation distance and suggests the path to further extending this distance.