Absolute instability of acoustic wave in semiconductor plasma: relativistic effects

Present paper reports the impact of relativistic effects on the acoustic wave instability in the semiconductor plasma medium. The classical hydrodynamic model has been used to derive dispersion relation of acoustic wave. A close inspection of dispersion relation inclusive of the relativistic effects admits the possibility of propagation of four modes in the laser semiconductor plasma system under study. Analysis of all these modes has been done quantitatively as well as qualitatively as a function of laser pump field intensity and doping concentration of the medium. The subsequent numerical analysis is made with n-InSb at 77 K duly irradiated by a 1.06 mu m Nd:YAG laser. Applied laser intensity is well below the damage threshold of the InSb crystal. The phase profile of observed modes confirms the existence of two co-propagating and two contra-propagating modes. The phase speed of I and IV modes are found to be augmented, whereas II and III modes are found to modify the gain profile of all the modes effectively. It is found that the propagation and amplification characteristics of all the modes get modified when relativistic effects are taken into account. It is found that proper selection of laser pump field intensity and carrier density plays a significant role in the favourable propagation and gain characteristics of the acoustic wave in the semiconductor plasma medium.