Characterization of self-sustaining filaments in low pressure conditions

Laser filaments can project high intensities in a small spot size over long distances making them advantageous for long-range applications, including applications that may require propagation to or at high altitudes. Previous studies have evaluated the impact of change in pressure on filamentation; however, they have neglected to ensure that propagation is in the self-sustained filament regime. In this laboratory-scale study, the laser preconditions have been carefully selected to ensure nonlinear propagation and filament formation from 1-0.15 atm. At each pressure investigated, the initial power to produce filaments (P_fil), the filament diameter and spectral broadening are characterized. These results indicate some divergence of the pressure scaling of P_fil from the predictions of theory.