Harmonic generation in coherent two-photon interaction between high-power optical pulses and resonant media

A theoretical investigation is made of collinear propagation of high-power optical pulses through a medium under conditions of two-photon resonance ω₀±ω_s≈ω₂₁ (ω₀ and ω_s are the pulse frequencies, ω₂₁ is the frequency of an atomic transition in the medium). It is assumed that the condition for coherent interaction τ₀, τ_s < T₂ is satisfied (τ₀ and τ_s are the pulse durations at the entrance, T₂ is the phase relaxation time of the medium). By means of numerical integration of equations for the fields and the medium, it is shown that efficient generation of the harmonics ω₁ = 2ω₀ ± ω_s, ω₂ = 2ω_s ± ω₀ is possible under short and ultrashort pulse conditions.