Filamentation laser femtoseconde IR : Interaction de deux filaments et Source de rayonnement secondaire longue distance

摘要

Amplified femtosecond laser systems allow, due to their high power, to explore new physical phenomena such as filamentation laser, where the laser beam propagates over long distances while maintaining a high peak intensity. Laser filament is actually a dynamic competition between Kerr effect (which focuses the beam) and defocusing due to plasma generation by the laser pulse. In this thesis the filamentation of a femtosecond IR laser beam was investigated both in terms of non-linear processes, and as a remote secondary radiation source, which can be displaced over long distance. For long propagation distances (km) the formation of several filaments is inevitable. First the interaction between two filaments has been studied methodically, and the effect of this interaction on the secondary radiation generated by filamentation has also been investigated. Then the generation of white light continuum and conical emission by laser filamentation and the ability to generate a white light continuum over long distances has been studied. Finally, a study on a field allowing propagation over 2 km was completed. We were able to demonstrate the possibilities to obtain filaments at a distance of 1 km with a femtosecond laser of 200 mJ propagating horizontally in the open air. This is, to date, the world record for long-distance laser filamentation.