Long range atmospheric laser propagation and filamentation-modulation instabilities

Long-range propagation of laser pulses in the atmosphere has numerous applications. In this presentation, we analyze and numerically simulate the propagation of laser pulses over distances >50km in the vertical direction. A dynamic equilibrium is derived where the spot size, pulse duration, wavefront curvature, phase, and chirp evolve self consistently along the path of propagation. The model takes into account the variation of air density, linear and nonlinear dispersion, and turbulence with altitude. By tailoring the initial chirp, wavefront curvature, and ratio of laser power to nonlinear focusing power, the pulse can be focused at remote locations with significant intensity enhancements. The hybrid filamentation-modulation instability, which is responsible for transverse and longitudinal beam breakup, is analyzed and numerically simulated. Our model allows for simulation of propagation over distances that would be computationally challenging using full scale wave-optic codes.