Exploring the limits to energy scaling and distant-target delivery of high-intensity midinfrared pulses

We numerically investigate the scaling behavior of midinfrared filaments at extremely high input energies. It is shown that, given sufficient power, kilometer-scale, low-loss atmospheric filamentation is attainable by prechirping the pulse. Fully resolved four-dimensional ($xyzt$) simulations show that, while in a spatially imperfect beam the modulation instability can lead to multiple hot-spot formation, the individual filaments are still stabilized by the recently proposed mechanism that relies on the temporal walk-off of short-wavelength radiation.

Figure 1

Peak on-axis intensitys vs propagation distance for three different pulses. Dashed blue line: 24-fs, 1.5-cm input beam from [7]. Solid red line: 24-fs, 3-cm beam simulated under the assumption of axial symmetry over 200 m. Black line: 350-fs chirped pulse with a 9-cm beam waist simulated over a 1-km propagation distance (with the assumption of axial symmetry).

Figure 2

Bottom: Peak intensity (solid black line) and integrated plasma density (dashed magenta line) vs propagation distance of a 350-fs chirped pulse with a 9-cm initial beam waist containing initial perturbations. Top: Total approximate energy contained in the computational box vs propagation distance. Simulation in xyzt.

Figure 3

Imperfect pulsed mid-IR beam breaking up in multiple filaments. $\mathit{XY}$ cross section of fluence snapshots of the chirped 350-fs, 9-cm, 4-$\mu \mathrm{m}$, 2.87-J wave packet with initial perturbations shown at various positions along the propagation distance. The dashed square in the second subfigure of first line indicates the region shown in the subsequent snapshots ($10\times 10$ cm). Simulation in xyzt. See supplementary video online [14].