Stimulated Raman effect and four-wave mixing in a hollow waveguide

A theoretical and experimental investigation of stimulated Raman scattering and four-wave mixing in a gas-filled hollow waveguide was performed. The four-wave mixing processes, specifically the generation of the third Stokes component at ω₃ when ω₃ =2ω₂-ω₁, show a strong resonance-like behavior as a function of wavelength. These resonances are caused by the phase matching required for efficient four-wave mixing, because the hollow waveguide supports only certain propagation directions leading to the development of waveguide modes. The theoretical results are compared with experimental data for TEM₀₀ and TEM₁₀ fundamental dye-laser beams generating third Stokes wavelengths between 2.6 and 7.5 μm