M.Sc Thesis

M.Sc StudentOrr Itai
SubjectLong-Lived Atmospheric Waveguides in the Wake of Laser
DepartmentDepartment of Physics
Supervisor PROF. Oren Cohen
Full Thesis textFull thesis text - English Version


Propagation of a high-intensity femtosecond pulse in the atmosphere can form a laser filament where diffraction is dynamically balanced by self-focusing and plasma generation. An atmospheric filament pulse initiates complex nonlinear dynamics in the densities of free electrons, ions, air density and in the level of molecular alignment that can induce atmospheric optical waveguiding. However, until recently it was generally believed that the induced waveguides die out after several nanoseconds. This severely limits any cw application of laser filamentation, because the repetition rate of any high power laser used for creating the filament is low, hence for most of the time between pulses light would not be guided.

Recently, our group discovered long-lived (microsecond-scale) optical waveguiding in the wake of atmospheric laser filaments which is generated by the acoustic waves that are formed by the filaments. During this master thesis, the author explored atmospheric waveguides in the wake of both single and two consecutive laser filaments. The results suggest that two filaments induce better waveguide than a single filament, because the succeeding filamenting pulse is guided in the waveguide that was induced by the leading pulse. In another experiment, the author demonstrated that the long-lived (microsecond-scale) atmospheric waveguide is robust to wind. Finally, the author explored the long-lived wakes of filaments interaction, both parallel filaments and colliding filaments.