Linear and nonlinear optical properties of realistic quantum-wire structures: The dominant role of Coulomb correlation

A systematic analysis of the linear and nonlinear optical properties of realistic quantum wires is presented. The proposed theoretical approach, based on a set of generalized semiconductor Bloch equations, provides a full three-dimensional multisubband description of carrier-carrier correlation for any profile of the confinement potential, thus allowing a direct comparison with experiments on available structures. In agreement with previous investigations based on simplified one-dimensional models, our analysis shows that, also for realistic quantum-wire structures, electron-hole Coulomb correlation completely removes the one-dimensional band-edge singularities from the linear-absorption spectra. Moreover, we find that this effect is present also at high densities (corresponding to gain regimes) and contributes significantly in suppressing the ideal sharp features of the free-carrier density of states. The multisubband nature of available state-of-the-art structures is found to play a dominant role in determining the overall spectral shape in the whole density range.