Field strength scaling in quasi-phase-matching of high-order harmonic generation by low-intensity assisting fields

Abstract

High-order harmonic generation in gas targets is a widespread scheme used to produce extreme ultraviolet radiation, however, it has a limited microscopic efficiency. Macroscopic enhancement of the produced radiation relies on phase-matching, often only achievable in quasi-phase-matching arrangements. In the present work we numerically study quasi-phase-matching induced by lowintensity assisting fields. We investigate the required assisting field strength dependence on the wavelength and intensity of the driving field, harmonic order, trajectory class and period of the assisting field. We comment on the optimal spatial beam profile of the assisting field.

Phase matching and quasi-phase matching of high-order harmonic generation—a tutorial

“…In the same vain, it was noted [142] that because the phase mismatch is approximately linearly dependent upon the harmonic order, superposing several spatial modes to construct a periodic modulation with a specific fundamental spatial frequency can be used to quasi-phase-match simultaneously many harmonic orders, with, perhaps surprisingly, the same relative enhancement. A relatively recent study analyzed the optimal amplitudes for fields at different superposition of spatial modes while being used as a perturbation to realize all-optical QPM [143].…”

Quantum-mechanical elaboration for the description of low- and high-order harmonics generated by extended gas media: prospects to the efficiency enhancement in spatially modulated media

“…The quantum-mechanical equations were solved for the case of limited number of wells, hence, the results can be applied to the thin solids only and they hardly can be applied to the atomic gas response simulations, while using the Kronig-Penny potentials is very time consuming to take into account the real number of atoms with different distances between them. There are also some models which take into account the macroscopic effects but do not solve the problem of any individual atom dynamics [10][11][12]. On the other hand, there are some approaches that are based on the analysis of the quantum-mechanical problem for the limited number of atoms (5 atoms), but they are not took into account the dispersion properties of macroscopic media and very serious approximations are used for the time dependent Schrodinger equation solving [13].…”

Generation of Attosecond Light Pulses from Gas and Solid State Media

“…The high number of interacting atoms, required to achieve a high XUV flux, in this case is confined in a small volume. (c) Quasi phase matching: Various quasi phase matching techniques have been applied for gas HHG to reduce the phase mismatch naturally accompanying the nonlinear process see [114,115] and references therein. In these arrangements either the target or the propagating laser beam is periodically modulated (by means of successive gas targets, propagation of the beam in a modulated waveguide or superposing a secondary modulating laser beam counter-or perpendicularly propagating with the generating laser pulse).…”