Superfilament Spatial Dynamics and Energy Deposition under Various Focusing Conditions

One of the distinctive features of femtosecond laser filamentation is intensity and plasma concentration clamping. Arising due to the dynamical competition between Kerr focusing and plasma defocusing this phenomenon limits the peak intensity to the values 1014 W/cm2 and plasma concentration level to 1016 −1017 cm−3. Further increase of the beam power leads to the beam splitting and multifilament formation rather than to an intense single filament with high plasma density. However it have been recently shown that fusing several filaments by introducing additional weak focusing one can obtain significant enhancement of energy deposition in the extended region around the focus resulting in higher plasma concentration and intensity [1,2,3].