Abstract
In the present communication, the hydrodynamic model is used to investigate the amplitude modulation as well as demodulation of an electromagnetic wave of high power helicon pump wave into another helicon wave in strain dependent dielectric material incorporating carrier heating (CH) effects. The consideration of CH in modulation and demodulation is prime importance for the adding of new dimension in analysis of amplification of acoustic helicon wave. By using the dispersion relation, threshold pump electric filed and growth rate of unstable mode from the modulation and demodulation of the high power helicon wave well above from the threshold value will be discussed in the present analysis. The numerical analysis is applied to a strain dependent dielectric material, BaTiO3 at room temperature and irradiated with high power helicon wave of frequency 1.78 × 1014 Hz. This material is very sensitive to the pump intensities, therefore during studies, Gaussian shape of the helicon pump wave is considered during the propagation in stain dependent dielectric material and opto-acoustic wave in the form of Gaussian profile (ω0,κ0) is induced longitudinally along the crystallographic plane of BaTiO3. Its variation is caused by the available magnetic field (ωc), interaction length (z) and pulsed duration of interaction (τ). From the analysis of numerical results, the incorporation of CH effect can effectively modify the magnitude of modulation or demodulation of the amplitude of high power helicon laser wave through diffusion process. Not only the amplitude modulation and demodulation of the wave, the diffusion of the CH effectively modifies the growth rate of unstable mode of frequency in BaTiO3. The propagation of the threshold electric field shows the sinusoidal or complete Gaussian profile, whereas this profile is found to be completely lost in growth of unstable mode. It has also been seen that the growth rate is observed to be of the order of 108 - 1010 s-1 but from diffusion of carrier heating, and that its order is enhanced from 1010 - 1012 s-1 with the variation of the magnetized frequency from 1 to 2.5 × 1014 Hz.
Highlights
A number of extensive researches have been carried out from the different researchers in worldwide to investigate the effect of modulation and demodulation of high power pump wave from nano-pulsed laser action
The numerical results of the possibility of modulation instability and the amplification of the acousto-helicon wave which arising from interaction of the pump helicon wave with acousto-helicon wave have been analyzed through Equations (28) and (29) for strain dependent dielectric material
The carrier heating on acousto-helicon interaction modifies the dependent parameter such as electron momentum transfer collision frequency (MTCF) (Equation (7)) and diffusion of charge carrier at the different temperature (Equation (10))
Summary
A number of extensive researches have been carried out from the different researchers in worldwide to investigate the effect of modulation and demodulation of high power pump wave from nano-pulsed laser action. The frequency modulated beam in less dispersive acoustic media is amplified due to excess charge carrier from enhanced diffusion They reported the excitation of an acousto-helicon wave modulation of plasma wave in longitudinally (k, k0, k1 ‖ ‖ Bs) magnetized semiconducting plasma [10]. The considerable gain in frequency is obtained from the nonlinear interaction of pump-helicon wave (ω0 , k0 ) with a transversely acoustic wave (ω, k ) and another helicon wave (ω1, k1 ) in cubic semiconductor plasma [11] In this present article, our analysis can be employed to see the effect of hot carriers on the amplitude modulation instability of an intense helicon pump wave due to acoustic-optic interaction in diffusive strain dependent dielectric constant. The applied electric field generates the sinusoidal threshold electric field and acoustic wave in acousto-optic modulator which can enhance the hyperbolic growth rate for the amplitude modulation and demodulation of the acoustic wave frequency in diffusive strain dependent dielectric constant in presence of strong magnetic field and hot carrier
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