Electron-impact excitation of W40+–W43+ ions: Cross-section and polarization

Electron-impact excitation of tungsten ions [Formula: see text] has been studied using the fully relativistic distorted wave (RDW) theory. The excitation cross-sections of selected electric dipole allowed transitions of these ions to be determined for the incident electron energies from the excitation threshold to 20 keV. Further, the calculated cross-section results are fitted with an analytical expression for direct applications in plasma modeling. In addition, using the density matrix theory, the linear polarization of the photons emitted from the excited tungsten ions when decay to their respective ground states is presented.

Spontaneously generated coherence in ladder-plus-Y double quantum dot system

A model was presented for linear susceptibility in ladder-plus-Y configuration of double quantum dot system using density matrix theory and including spontaneously generated coherence of Λ-type system. Wetting layer and quantum dot inhomogeneity were considered in the calculations, which gives a practical description of double quantum dot structures well. With increasing spontaneously generated coherence from Λ-component, the dispersion was increased and shifted under spontaneously generated coherence. The inclusion of wetting layer under spontaneously generated coherence increases gain which coincides with the published results. A possibility of slow light was predicted.

Current-constrained one-electron reduced density-matrix theory for non-equilibrium steady-state molecular conductivity

In the effort to create ever smaller electronic devices, the idea of single molecule circuit elements has sparked the imagination of scientists for nearly fifty years.

Performance characteristics of GaN/Al0.2Ga0.8N quantum dot laser at L=100Å

In this paper, a theoretical model is used to study the optical gain characteristics of quantum dot lasers. The model is based on the density matrix theory of semiconductor lasers with relaxation broadening. The effect of doping with varying the side lengths of the box in the structure is taken into account. A comparative study of the gain spectra of p-doped, undoped and n-doped structures of cubic quantum-dot (QD) laser respectively, is presented for various side lengths. The variation of peak gain on carrier density is also presented. The effect of side length on the variation in modal gain versus current density is plotted too. The results indicate that the p type doping is efficient to reach a better optical gain value, and to achieve low threshold current densities compared with undoped and n-doped structures, and the optimum value for quantum dot width to achieve the lower threshold current density for the three cases is L=100A .