Plasma defocusing

Picosecond pedestal, 143 Pin-hole camera, 128 Plasma channels, 112, 147, 148 Plasma defocusing, 84, 91 Plasma frequency, 166 Plasma index of refraction, 147 Plasma mirror (PM) technique, 194 Plasma wakefield acceleration, 172 Plasma wavelength, 166 Plasma-induced effects, 83 Polarization, 97 Polarization control, 87 Ponderomotive force, 170 Population inversions, 19 Post-irradiation spectroscopy, 156 Pre-pulse, 143 Propagation, 81 Protein, 102 Pump depletion, 151... 

Kerr effect focuses An =n 2 l Plasma defocuses An = - N(l) / 2Ncrit... 

Fig. 6.2. Mechanism of filamentation. (a) Kerr effect (self-focusing) (b) defocusing by the plasma...

The initial perturbations grow rapidly and reach intensities high enough to ionize air (second panel). Collapse of a filament is eventually regularized by plasma induced defocusing. That causes decay of the filament and returns... 

If a 50 pm droplet is inserted in the centre of the filament at d = 1 m after the filament onset, the filament appears unperturbed, although the dynamical balance between Kerr self-focusing and defocusing on the plasma plays a critical role due to the strong non-linearity of the filamentation process. Moreover, the filament length is not affected by the interaction with the droplet. Comparing the filament energy with and without droplet shows very limited losses. Shortly after the interaction with the droplet, the loss is only... 

Fig. 10.22 Focusing (a) and defocusing (b) of a laser beam in the atmosphere due to the Kerr lens effect and plasma formation. The laser beam cross-section looks like a row of short sausages...

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