Acousto-optic modulation in magnetised diffusive semiconductors
Acousto-optic modulation in magnetised diffusive semiconductors
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DOI：
10.1140/epjd/e20020073
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发表时间：
2002-05
期刊：
影响因子：
--
通讯作者：
S. Ghosh;M. Rishi
中科院分区：
文献类型：
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作者：
S. Ghosh;M. Rishi
本文分析了在横向磁化等离子体介质中声光效应对强流电磁束的调制。利用耦合模理论详细研究了载流子扩散对调制波阈值场和增益分布的影响。AO相互作用的起源被假定为在于介质的诱导非线性扩散电流密度。将调制过程看作四波参量相互作用，导出了描述这种现象的有效三阶AO极化率表达式。由于声学模式的介电弛豫，传播特性如色散和衍射极大地修改了调制。阈值泵浦场和稳态增长率估计从有效的三阶极化等离子体介质。分析估计表明，在存在的增强扩散，由于过剩的电荷载流子的调制光束可以有效地放大在一个dispersionless声波制度。外部直流磁场的存在下，被发现是有利的发病扩散诱导调制放大的调制波在重掺杂制度。
The modulation of an intense electromagnetic beam induced by the acousto-optic (AO) effect has been analysed in a transversely magnetised semiconductor-plasma medium. The effect of carrier diffusion on the threshold field and gain profile of the modulated wave has been extremely investigated using coupled mode theory. The origin of the AO interaction is assumed to lie in the induced nonlinear diffusion current density of the medium. By considering the modulation process as a four wave parametric interaction an expression for effective third-order AO susceptibility describing the phenomena has been deduced. The modulation is greatly modified by propagation characteristics such as dispersion and diffraction due to dielectric relaxation of the acoustic mode. The threshold pump field and the steady state growth rates are estimated from the effective third-order polarisation in the plasma medium. Analytical estimation reveals that in the presence of enhanced diffusion due to excess charge carriers the modulated beam can be effectively amplified in a dispersionless acoustic wave regime. The presence of an external dc magnetic field is found to be favourable for the onset of diffusion induced modulational amplification of the modulated wave in heavily doped regime.