This paper presents an analytical investigation of nonlinear absorption coefficient and refractive index of the Raman scattered stokes mode resulting from the nonlinear interaction of an intense pumping light beam with molecular vibrations of semiconductor-plasma. The origin of this nonlinear interaction lies in the third-order (Raman) susceptibility arising from the induced current density and density fluctuations generated within the medium. The total refractive index and absorption

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... t are determined through the effective susceptibility derived with the help of coupled-mode theory of plasmas. The effect of Szigeti effective charge (q) and magnetic field (β 0) has been introduced through equation of motion of lattice vibration and Lorentz force, respectively. The numerical estimates are made for n-type InSb crystal duly irradiated by a 10-nanosec pulsed 10.6 µm CO 2 laser. The Szigeti effective charge contributes the Raman susceptibility at moderate excitation intensity. At high excitation intensity, the contribution of Szigeti effective charge is wiped off and nonlinearity in the medium is only due to differential polarizability. In the absence of Szigeti effective charge, the magnitude of Raman susceptibility is found to agree with other theoretical quoted values. The analysis establishes that a small absorption coefficient and large refractive index can easily be obtained by proper selection of magnetic field and doping concentration under moderate excitation intensity in weakly polar semiconducting crystals which proves its potential as candidate material for the fabrication of cubic nonlinear devices.