Propagation of self-guided laser filaments through air and other gases results in a rich variety of phenomena and applications, including induction of optical waveguides through molecular alignment and plasma. However, these waveguiding effects die out approximately one nanosecond after the propagation of the filementing pulse.
We discovered that a filament induces intricate dynamics of the air density that gives rise to a transient positive index-change at the center of the filament wake. We demonstrate waveguiding through this induced positive index-change that lasts for more than a microsecond. In addition, we observe and study the formation of ultra-short acoustic waves and subsequently their outward propagation at the speed of sound. These induced long- lived waveguides can be useful for numerous applications of laser filemantation in the atmosphere, from power transmission through these channels to backward propagation of coherent and incoherent radiation for remote sensing.