Short-pulse lasers for weather control

Abstract

Filamentation of ultra-short TW-class lasers recently opened new perspectives in atmospheric research. Laser filaments are self-sustained light structures of 0.1-1 mm in diameter, spanning over hundreds of meters in length, and producing a low density plasma (10-10 cm) along their path. They stem from the dynamic balance between Kerr self-focusing and defocusing by the self-generated plasma and/or non-linear polarization saturation. While non-linearly propagating in air, these filamentary structures produce a coherent supercontinuum (from 230 nm to 4 µm, for a 800 nm laser wavelength) by self-phase modulation (SPM), which can be used for remote 3D-monitoring of atmospheric components by Lidar (Light Detection and Ranging). However, due to their high intensity (10-10 W cm), they also modify the chemical composition of the air via photo-ionization and photo-dissociation of the molecules and aerosols present in the laser path. These unique properties were recently exploited for investigating the capability of modulating some key atmospheric processes, like lightning from thunderclouds, water vapor condensation, fog formation and dissipation, and light scattering (albedo) from high altitude clouds for radiative forcing management. Here we review recent spectacular advances in this context, achieved both in the laboratory and in the field, reveal their underlying mechanisms, and discuss the applicability of using these new non-linear photonic catalysts for real scale weather control.

Molecular quantum wakes for clearing fog

“…With 1.5 × 10 5 cm −3 droplets in a channel of 0.5 mm radius and 10 cm length, this leads to Q = 13 mJ, which means that all the incoming laser energy should be deposited in the gas and then transferred from the heated gas to the droplets with an efficiency of 100%. These considerations suggest that the droplet vaporization by the heated gas does not play the major role in the fog clearing process, in contrast to the displacement of the drops by the acoustic wave as previously observed for the filament induced clearing process [8,9,37].…”

Free space laser telecommunication through fog

“…Moreover, the laser energy was deposited in the first meters of the optical path, according to the usual Beer-Lambert exponential decay.The 2000's saw the emergence of femtosecond TW-class lasers (1 TW = 10 12 W), hence the opportunity to reconsider laser transmission through fog with a fundamentally different approach: non-linear propagation in the atmosphere and laser filamentation [18]. Due to the high peak-power, focusing (Kerr effect) and defocusing (Kerr saturation, plasma generation) non-linearities involved in the propagation lead to the formation of laser filaments [19][20][21][22][23]. Laser filaments are self-sustained light structures of typically 100 µm diameter (at 800 nm) and up to hundreds of meters in length, widely extending the traditional linear diffraction limit.…”

Optical beaming of electrical discharges

“…In addition, the technique we propose pertains to atmospheres with a different gas composition and/or pressure level. Furthermore, low power continuous wave operation ensures ease of implementation and paves the way for a range of applications such as controlling high voltage systems 1 , microfabrication and machining 3 , 4 , precision microsurgery and cancer treatment 8 – 12 , and controlling atmospheric lightning 2 , 33 .…”