Arrangement of multiple UV filaments by periodic amplitude masks

Nonlinear self-focusing of sub-TW power, sub-ps UV pulses generated by Ti:Sapphire/KrF GARPUN-MTW laser facility produces a few hundred randomly distributed filament-like weakly ionized plasma channels in atmospheric air. Arrangement of occasional multiple filaments has been demonstrated by means of amplitude masks with periodic circular and square apertures introduced in the light beam. Diffraction on the apertures overcomes natural stochastic and deterministic radiation inhomogeneities and builds up a regular array of a few hundred filaments persisting over 20 m.