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Parametric Excitation in Magnetoactive Doped Piezoelectric Semiconductor
Pradeep K. Gupta and Pranay K. Sen

The paper reports the detailed analytical investigation of parametric excitation in a doped weakly piezoelectric noncentrosymmetric magnetoactive semiconductor. We have used the hydrodynamic model of a one-component (electron) semiconductor plasma and followed the coupled mode approach. The electrostrictive contribution of the crystal medium on the nonlinear optical process has also been incorporated. The nonlinear induced current density; the second-order effective polarization and the corresponding effective optical susceptibility are obtained under off-resonant laser irradiation limit. The analysis deals with the qualitative behaviour of the threshold condition for the onset of parametric excitation, the anomalous parametric dispersion and the gain mechanism with respect to the excess doping concentration and pump electric field. Numerical estimates are made for n-InSb magnetoactive crystal at 77 K duly shined by a 10.6 μm nanosecond pulsed CO2 laser. Special efforts are made for optimization of the doping level, magnetic field and pump electric field to achieve maximum parametric amplification at pump fields much below the optical damage threshold. The analysis suggests that the threshold pump field required for the onset of parametric processes can be considerably reduced by selecting a properly doped piezoelectric magnetoactive semiconductor which may even lead to either positive or negative enhanced parametric dispersion. Such dispersion can be of great use in the generation of squeezed states. The analysis shows that electrostriction plays a trivial role on parametric excitation in the magnetoactive semiconductor crystal.

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