Conversion of radiation frequency in four-wave parametric resonance processes based on stimulated Raman scattering

A theoretical analysis is made of the interaction between fields whose frequencies satisfy the relationship ω_p–ω_s=ω_g±ω_a≈ω₂₁ , where ω_p, ω_s, ω_g and ω_a are the frequencies of the pump, Stokes, generated, and auxiliary fields; ω₂₁ tne frequency of a transition between two levels in the investigated susbstance. The conditions are established for the maximum efficiency of the conversion of the fields ω_p and ω_a into the field ω_g. It is shown that the optimal conversion conditions are obtained for a certain ratio of the pump and auxiliary field powers when the phases of the interacting waves are locked. Numerical estimates are obtained of the conversion efficiency and interaction length when the active substance is potassium vapor or compressed hydrogen.