Remote atmospheric breakdown using intense femtosecond laser pulses

Abstract

Summary form only given. A remote atmospheric breakdown (RAB) induced by an intense laser pulse is a very rich source of ultraviolet (UV) and broadband visible light generated by various nonlinear and ionization processes. These radiation could provide the source for active remote sensing of environmentally hazardous components through spectroscopic detection and identification. The location of the RAB can be controlled when intense femtosecond laser pulses are used. The inherent broad bandwidths of the laser pulses allow a low-intensity negatively chirped laser pulse to be compressed in time due to the group velocity dispersion and focused transversely due to non-linear self-focusing. The rapid increase in the laser intensity near the focal region can cause ionization and harmonic generation in the UV and visible regimes. Proof of principle laboratory experiments are being performed at the Naval Research Laboratory on the generation of RAB and the spectroscopic detection of mock biological hazards. We have demonstrated pulse compression in long-distance atmospheric propagation, laser filamentation, harmonic generation, air breakdown, and induced fluorescence that are controlled by both the initial temporal chirp and the induced laser pulse mode structures. Preliminary experimental results will be presented.