Throughout history, there has been a longstanding aspiration to prevent or mitigate the impact of destructive weather events such as floods, droughts, hailstorms, and lightning strikes, thus, driving a continuous interest in diverse weather modulation methods. Lightning is a fascinating and destructive manifestation of nature.
This thesis work showcases the study and the application of simultaneous high-average and high-peak power lasers for (a) the protection from atmospheric electric discharges and (b) long distance optomechanical clearing of aerosols for free-space optical telecommunication.
The new generation of thin-disk lasers allowed us to scale up laboratory experiments to real life atmospheric application, with typically 50 m long laser-induced filaments. While the concept of a laser lightning rod emerged nearly 50 years ago, this thesis deals first with the characterization of the non-linear regime of the light from the thin-disk laser prototype delivering 500 mJ, 1 kHz, 1 ps at 1030 nm. To this end, we first report Second Harmonic Generation (SHG) and Third Harmonic Generation (THG) energy conversion efficiencies up to 59% and 27%, respectively. In a second time, we investigate the spatial evolution of the multiple filamentation regime using the fundamental beam at 1030 nm or using combination with the second and third harmonics.
The second part of this work deals with the presentation of the experimental work carried at 2500 m above sea level, and the demonstration of the firsts laser-guided lightnings from upward leaders. This experiment took place in the frame of Horizon 2020 program from the European commission of research. It is a unique consortium of seven companies, research institutes and universities including the University of Geneva. The large electromagnetic spectrum emitted from the lightnings, during propagation and at the lightning rod impact, was characterised with VHF interferometry, high-speed cameras, X-ray bursts sensor, tower current, and more.
The last part of this work presents (a) the characterisation of the effect of the laser repetition rate on the filamentation process, and (b) the long distance clearing mechanism of clouds for the application of free-space optical telecommunication.
At 1030 nm, the density hole left in the wake of the filament and its length exhibits a strong dependence, for repetition rates from 10 to 100 kHz.
Preliminary measurements of meter scale artificial cloud drilling using laser filamentation show the potential of a first free-space optical telecommunication for real life application.
These experimental breakthroughs open the way for new atmospheric applications of ultrashort high peak- and average- power ultrashort laser systems, for meteorological studies and high-tech weather protections.
