Parametric excitation of electron-acoustic waves in magnetised semiconductor plasmas

Based on the hydrodynamic model of a plasma, the parametric excitation of an electron-acoustic wave by a pump laser beam in a semiconductor-plasma, viz., InSb, is investigated analytically in the presence of a magnetic field where the nonlinearity arises due to the ponderomotive force on the electrons. A general nonlinear dispersion relation is derived and solved for both, the isotropic (B0 = 0) case and the magnetoactive (B0 not= 0) one. The threshold value of the pump electric field and the growth rate of the excited mode are obtained for the case of n-type InSb at 77 K. The effect of the magnetic field is found to reduce the threshold electric field as well as the growth rate of the excited wave. From numerical calculations, it is found that when B0 = 2 T, the threshold value of the electric field as well as the growth rate of the excited mode well above the threshold decrease to about 0.5 times that in a nonmagnetic situation. (author)