Nondegenerate diffraction on transient gratings in InSb

Nondegenerate diffraction in InSb has been investigated. In experiments, the grating is excited by two CO laser beams with the frequency omega /sub 1/, and a third beam with a different frequency omega /sub 2/ is used to detect the grating. The diffraction efficiency can be represented by the nonlinear susceptibility chi /sup (3)/( omega /sub 2/, - omega /sub 2/, omega /sub 1/), which can be obtained with the Bloch equation. The frequency dependence given by theory is in agreement with experiments, implying that the nonlinear index is caused by the saturation.<
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