Gain Dynamics of the N2+ Air Laser

Abstract

Lasing from femtosecond laser filaments is a relatively new field of study that has been studied since its first observation in 2003. Such lasing effect is of interest to the scientific community due to its possible application in remote sensing. This thesis studies the lasing dynamics of the excited molecular nitrogen ion N2+ which emits primarily at 391 nm and 428 nm wavelengths. We start by studying the ellipticity dependence of the gain from filaments in ambient air. We then study the ellipticity dependence in a vacuum in a supersonic gas jet to remove the complexity of filamentation. We show that recollision doesn't play a significant role in creating a population inversion by comparing the ellipticity dependence of the gain and high harmonic generation. The rest of this thesis is devoted to shining some light on another possible mechanism. We characterize the gain by its temporal profile, jet position dependence, and density dependence.