Modeling the generation of optical modes in a semiconductor waveguide with distributed feedback formed by a space charge wave

The amplification and generation of optical TE waves arising on a lattice formed by a space charge wave in a planar waveguide based on a donor-doped semiconductor (gallium arsenide) n-GaAs are considered. The region of interaction is limited by contacts with a constant electric field applied between them, which, while operating in the Gunn oscillations suppression mode, gener-ates a small-signal periodic inhomogeneity. Reflection and transmission regimes for same-index TE modes propagating in the waveguide structure are investigated depending on the phase mis-match and the pump level. It is shown that even with a relatively small modulation depth of the di-electric constant (about 10–5), under conditions of high optical pumping (with a gain of about 150 cm–1) and a corresponding detuning from phase matching there is the possibility of not only ampli-fying the direct and backward (reflected) optical modes, but also their generation. The advantage of the considered effects is that they enable flexible control of parameters of the dynamic lattice. The results obtained can be used to create semiconductor laser generators based on the interaction of the optical modes and a space charge wave.

Characteristics of Nonthermal Dupree Diffusion on Space-Charge Wave in a Kappa Distribution Plasma Column with Turbulent Diffusion

The nonthermal diffusion effects on the dispersion equations of ion-acoustic space-charge wave (SCW) in a nonthermal plasma column composed of nonthermal turbulent electrons and cold ions are investigated based on the analysis of normal modes and the separation of variables. It is found that the real portion of the wave frequency of the SCW in a Maxwellian plasma is greater than that in a nonthermal plasma. It is also found that the magnitude of the damping rate of the SCW decreases with an increase of the spectral index of the nonthermal plasma. It is also shown that the magnitude of the scaled damping rate increases with an increase of the Dupree diffusion coefficient. Moreover, the influence of the nonthermal character of the nonthermal plasma on the damping rate is found to be more significant in turbulent plasmas with higher diffusion coefficient. The variations of the wave frequency and the growth rate due to the characteristics of nonthermal diffusion are also discussed.

Resonant flow instability of space-charge waves in self-gravitating Lorentzian dusty plasma columns

The dispersion characteristics and the resonant instability mode of the space-charge wave are investigated in a streaming Lorentzian dusty plasma column by using the normal mode analysis. The result shows that the non-thermal character of the Lorentzian cylindrical dusty plasma enhances the unstable property of the space-charge wave due to the beam–plasma interaction. It is found that the resonant growth rates of the space-charge wave increase with an increase of the harmonic-order of the root of the Bessel function. It is also found that the influence of the self-gravitation enhances the resonant growth rate of the space-charge wave of the Lorentzian cylindrical dusty plasma. In addition, it is found the resonant growth rate decreases with an increase of the radius of the dusty plasma column. The variation of the resonant instability mode due to the non-thermal character and geometric effects is also discussed.