White-Light Filaments for Atmospheric Analysis

TLDR

High‑power femtosecond pulses can form self‑guided filaments that emit broadband white light with directional backward scattering detectable from more than 20 km altitude, offering an alternative to traditional long‑path atmospheric spectroscopy that relies on ambient light or narrow‑band lasers. The study aims to use this broadband white‑light source for white‑light and nonlinear LIDAR of trace gases and aerosols, and to explore filament‑induced ionization for laser‑driven condensation and lightning control. To pursue these goals, the authors constructed the mobile femtosecond‑terawatt Teramobile laser system for atmospheric experiments.

Abstract

Most long-path remote spectroscopic studies of the atmosphere rely on ambient light or narrow-band lasers. High-power femtosecond laser pulses have been found to propagate in the atmosphere as dynamically self-guided filaments that emit in a continuum from the ultraviolet to the infrared. This white light exhibits a directional behavior with enhanced backward scattering and was detected from an altitude of more than 20 kilometers. This light source opens the way to white-light and nonlinear light detection and ranging applications for atmospheric trace-gas remote sensing or remote identification of aerosols. Air ionization inside the filaments also opens promising perspectives for laser-induced condensation and lightning control. The mobile femtosecond-terawatt laser system, Teramobile, has been constructed to study these applications.