A Multidisciplinary Research Initiative funded by the High Energy Laser – Joint Technology Office.
Filamentation of high-power femtosecond laser pulses in air has received much attention in the last decade. Yet many aspects of this phenomenon are still not well understood. Even the basic mechanism for stabilization of the filamentation in air has recently come into question in the latest theoretical studies. The nature of the carrier field, its extent and impact on the propagation and lifetime are not well understood. In particular we have little knowledge of the nature of the gaseous medium both during and following the propagation of the filament. Recent studies by some of our team have shown that molecular excitation effects in the filament gas may be playing a role. Unusual phenomena also seem to be associated with filaments made by UV laser beams; little white light is generated and other effects are unclear.
As we move into the realm of engineering matrices of filaments, with both spatially and temporally bundles of filaments propagating through the atmosphere, and with the innovations of Airy beam and Bessel bullet formation of filaments, we urgently need to resolve these fundamental scientific uncertainties on the basic formation of filaments. This is one of the two foci of this program. To this end we have teamed with experts in advanced modeling of filaments (Philip Sprangle, Navy Research Laboratory), molecular interactions in filaments (Tamar Seideman, Northwestern University), and UV filaments (Jean-Claude Diels, University of New Mexico). Our proposal therefore addresses the basic fundamental science of the interaction of the filament with air. We will study other gases, and gas combinations to elucidate the scientific mechanisms, but the overall objective is to obtain a firmer understanding of the interaction mechanisms and consequences of the filaments propagating through air.
A second focus of this proposal is to place the science of the interaction of filamented laser light with solid materials on a firmer basis. At UCF, we are the only American university to have a program of study in this area. At its basis is the study of laser-produced plasmas, a topic that we know well, has comprehensive diagnostics and modeling capabilities.