Air lasing through femtosecond filamentation (Conference Presentation)

Air lasing is a concept that is based on the utilization of the constituents of air as a gain medium in a standoff, impulsive, laser-like optical source. While both forward-propagating and backward-propagating laser emissions could be generated, the backward-propagating emission is of the most practical significance for its potential to enable single-ended remote sensing schemes. I will review recent results on air lasing from singly ionized nitrogen molecular ions N2+, pumped through femtosecond laser filamentation in air. So far, lasing has been demonstrated only in the forward direction, and the mechanisms that enable population inversion have been highly controversial.