Self-sustained plasma waveguide structures produced by ionizing laser radiation in a dense gas

Effect of plasma-core-induced self-guiding on phase matching of high-order harmonic generation in gases

“…Plasma-core induced self-guiding has been studied in detail by Sergeev and co-workers in previous publications [22,23,25,27]. Here we first summarize the most important aspects previously published, and extend them with findings that are most important for HHG.…”

“…The key presumption of the model used by Sergeev et al is that ionization is considered as a threshold-type process with respect to the strength of the laser field [22,23]. This is a fair assumption for tunneling ionization, since it depends highly nonlinearly on intensity.…”

“…[50]). In the two-dimensional case the plasma channel guiding the beam has a top-hat profile with 2d width [22].…”

“…At the same time, it is less often highlighted that for short pulses the rapid ionization can play a leading role in the guiding of a laser beam by the formation of a self-sustained plasma filament [22][23][24][25][26][27][28][29]. Plasma-core induced beam self-guiding has been studied up to now in the context of beam smoothing [30], frequency shifts [31] or other pulse propagation-related phenomena [28,32], but only a few times mentioned in relation to HHG in gases [29,[33][34][35][36][37].…”

Ionization-induced dynamics of ultrashort laser pulses focused in a dense gas

“…This effect leads to a number of interesting nonlinear phenomena such as ionization instabilities, 1 frequency up-conversion and pulse compression, 2-4 odd harmonic generation in linearly polarized light, 5 and long plasma channel guiding. [8][9][10] From practical point of view, recently significant attention was focused on the problem of waveguide writing in dielectric media by femtosecond laser pulses where field ionization is an inherent process. 11 We consider a collective nonlinear phenomenon -structural instability of ultrashort laser pulses focused in an ionizable medium.…”