(1) School of Studies in Physics, Vikram University, Ujjain-456 010, Madhya Pradesh, India, IN
Abstract:
Based on hydrodynamic model of plasmas an analytical investigation of frequency modulational interaction between copropagating
high frequency pump and acoustic mode and consequent amplification (steady-state and transient) of the modulated waves is
carried out in a magnetised piezoelectric semiconductor medium. The phenomenon of modulational amplification is treated as
four wave interaction process involving cubic nonlinearity of the medium. Gain constants, threshold-pump intensities and optimum-pulse
duration for the onset of modulational instabilities are estimated. The analysis has been performed in non-dispersive regime
of the acoustic mode, which is one of the preconditions for achieving an appreciable initial steady-state growth of the modulated
signal wave. It is found that the transient gain constant diminishes very rapidly if one chooses the pump pulse duration beyond
the maximum gain point. Moreover, the desired value of the gain can be obtained by adjusting intensity and pulse duration
of the pump and doping concentration of the medium concerned.
Received 12 August 1999 and Received in final form 17 December 1999