A high intensity femtosecond laser pulse that is propagating in the atmosphere can form a filament due to dynamical balance between self-focusing and plasm defocusing. The time scales of the physical effects supporting the filaments are very short: self-focusing and multiphoton ionization are instantaneous, while plasma effects survive a few nanoseconds after the femtosecond pulse has passed. For this reason, all waveguiding phenomena associated with femtosecond laser filaments were believed to last no more than a nanosecond. In contrast to this general belief, we have recently discovered that atomospheric filaments induce long-lived waveguides [1]. With the group of Mordechai Segev, we experimentally demonstrated waveguiding effects that live for a microsecond range, long after the plasma is gone. These waveguides are based on air density and acoustic waves effects.
- O. Lahav, L. Levi, I. Orr, R. Nemirovsky, Y. Nemirovsky, I. Kaminer, M. Segev, and O. Cohen, Long-lived waveguides and sound wave generation by laser filamentation, Phys. Rev. A 90, 021801(R) (2014)