Formation of a static hologram by different-frequency beams in Bi12SiO20 using a semiconductor laser

A static hologram was formed by beams of different frequencies (Ω = ω₁ – ω₂ = 2π X 50 Hz) in the presence of an external field E₀ cos(Ωt) in a Bi₁₂SiO₂₀ crystal at wavelengths λ = 0.79 μm (semiconductor laser) and λ = 0.763 μm (He–Ne laser). Dependences of the diffraction efficiency on the spatial frequency η (q) differed at these two wavelengths in such a way that η (0.79 μm) < η (0.63 μm) for q < 4 X 10³ cm^–1, but the dependences were practically coincident in the range q > 4 X 10³cm^–1.