title: Ultrahigh-order wave mixing in noncollinear high harmonic generation.
abstract: We show that noncollinear high harmonic generation (HHG) can be fully understood in terms of nonlinear optical wave mixing. We demonstrate this by superposing on the fundamental ω1 field its second harmonic ω2 of variable intensity in a noncollinear geometry. It allows us to identify, by momentum conservation, each field's contribution (n1,n2) to the extreme ultraviolet emission at frequency Ω = n1ω1 + n2ω2. We observe that the photon (Ω) yield follows an n2 power law on the ω2 intensity, before saturation. It demonstrates that, although HHG is a highly nonperturbative process, a perturbation theory can still be developed around it.
authors.affiliation: Joint Attosecond Science Laboratory, 100 Sussex Drive, Ottawa, K1A 0R6, Canada.
authors.forename: J B
authors.initials: JB
authors.lastname: Bertrand
authors.forename: H J
authors.initials: HJ
authors.lastname: Wörner
authors.forename: H-C
authors.initials: HC
authors.lastname: Bandulet
authors.forename: É
authors.initials: É
authors.lastname: Bisson
authors.forename: M
authors.initials: M
authors.lastname: Spanner
authors.forename: J-C
authors.initials: JC
authors.lastname: Kieffer
authors.forename: D M
authors.initials: DM
authors.lastname: Villeneuve
authors.forename: P B
authors.initials: PB
authors.lastname: Corkum