Filamentation of ultrashort pulse laser beams resulting from their propagation over long distances in air

TLDR

The study investigates the propagation of high‑power, short‑pulse laser beams over long distances in air through experimental measurements and numerical simulations. Experiments used 500 fs, 1053 nm pulses, and a numerical model based on the nonlinear Schrödinger equation coupled to a multiphoton ionization law was employed to describe the dynamics. Filaments appear after 5–10 m, propagate beyond 200 m, have diameters from 100 μm to several millimeters, initial plasma densities of a few × 10¹⁶ cm⁻³, and their energy stabilizes at 1.5–2 mJ after ~35 m, in agreement with the model.

Abstract

The propagation of high-power short-pulse laser beams over considerable distances in air is studied both experimentally and via numerical simulations. Filaments are formed after 5–10 m and their propagation over distances in excess of 200 m is reported for the first time. The lateral dimensions of the filaments are found to range from about 100 μm to a few millimeters in diameter. The early values of plasma electron density have been inferred to be a few times 1016 cm−3 using longitudinal spectral interferometry. For 500 fs pulses and a wavelength of 1053 nm, the energy in the filament can be quite high initially (∼8 mJ) and is found to stabilize at about 1.5–2 mJ, after about 35 m. A simple model based on the nonlinear Schrödinger equation coupled to a multiphoton ionization law appears to describe several experimental results quite well.