Optical Kerr effect field measurements and ad hoc engineering model comparisons

Optical Kerr effects induced by the propagation of high peak-power laser beams through real atmospheres have been a topic of interest to the nonlinear optics community for several decades. This paper proposes a new analytical model for predicting the filamentation/light channel onset distance in real atmospheres based on modulation instability model considerations. The normalized intensity increases exponentially as the beam propagates through the medium. It is hypothesized that this growth can be modeled as a weighted ratio of the Gaussian beam diameter at range to the lateral coherence radius and can be used to set the power ratio for an absorbing, turbulent, nonlinear media to estimate the beam collapse distance. Comparison of onset distance predictions with those found from computer simulation and deduced from field experiments will be presented. In addition, this model will be used with an analytical approach to quantify the expected radius of light channels resulting from self-focusing both with and without the production of a plasma filament. Finally, this paper will describe a set of 1.5-micron, variable focal length USPL field experiments. Comparisons of theoretical radius calculations to measurements from field experiments will be presented.