Analytical treatment of quasi-phase matching of high-order harmonics in multijet laser plasmas: influence of free electrons between jets, intrinsic phase, and Gouy phase

Abstract

An ab initio analytical model of quasi-phase matching in multijet laser plasmas is presented on the basis of the phase difference between harmonics. Phase mismatch compensation between jets is explained by the free electrons produced during laser ablation, while the Gouy phase shift of the driving pulse is considered insufficient for this purpose, as well as the intrinsic phase variation at experimental conditions. Inverse proportionality of the intensity of harmonics to the square of harmonic order is derived from the suggested model of propagation and should be considered when analyzing high-harmonic-generation spectra by a single-atom response even in the absence of propagation.

Effects of Laser Plasma Formation on Quasi-Phase Matching of High-Order Harmonics from Nanoparticles and Atoms

“…The simulations of QPM in plasmas has been reported in a few studies, thus providing different approaches in determination of the most important physical processes involved in artificially created conditions for maintenance of the optimal phase relations between the driving and harmonic waves [19,24,29,30]. Currently, the mechanism of QPM in LPP seems, to some extent, well determined.…”