Dispersion of the nonlinear optical susceptibility in n-InSb

Using a CO2 laser, we have observed the dispersive behavior of the third-order nonlinear optical susceptibility, χ(3)(-ω3,ω1, ω1,-ω2), in n-InSb in a magnetic field. The resonances occur when the difference frequency ω2-ω1 is near the cyclotron frequency, or twice the cyclotron frequency. A connection is drawn between the dispersion of χ(3) and the spontaneous and stimulated Raman scattering from Landau levels. A simple semiclassical theory shows the correct polarization properties and resonance behavior of χ(3) and is qualitatively in agreement with experiment. © 1971 The American Physical Society.