Space-time wave packets propagating a kilometer in air

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.