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

Abstract

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 bandedge singularities from the linear-absorption spectra. Moreover, we find that this effect is present also at high densities ͑corresponding to gain regimes͒ 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.

Coherent phenomena in semiconductors

“…In both cases, one finds a strong suppression of the 1D band-edge singularity, in agreement with previous results based on simplified 1D models 121,122 . This theoretical approach 123,124 is based on the general kinetic theory presented in section II, which allows a full 3D description of Coulomb interaction within a multiminiband scheme. In particular, we focus on the quasi-equilibrium regime where the solution of the coupled kinetic equations (44) simply reduces to the solution of the interband-polarization equation.…”

Franz-Keldysh effect and dynamical Franz-Keldysh effect of cylindrical quantum wires

“…The quantum confinement of the excitons on length scales smaller than the bulk Bohr radius leads to enhanced exciton peaks in optical absorption spectra of lowdimensional nanostructures. [1][2][3][4] Extensive work has been done to investigate the specifics of the excitonic optical properties of quantum wells, 1,2 quantum wires, [3][4][5][6] quantum dots, [7][8][9][10] and superlattices. [11][12][13][14][15][16] The optical spectra of semiconductor structures can be modified dramatically by the application of external static electric and/or magnetic fields.…”

“…In general, the SBEs are solved in k space. 5,26 However, solving the SBE in k space is much more formidable in numerical implementation, especially when external fields are applied. The advantages of the real-space approach are as follows: ͑i͒ it can be used as a probe into the wave-packet motion of the polarization, ͑ii͒ the Coulomb singularity can be resolved analytically by a polynomial finite element, ͑iii͒ bound, quasibound, and free states are included in the calculation, ͑iv͒ external fields can be added conveniently, and ͑v͒ it can be incorporated to implement a very efficient fast Fourier transform algorithm.…”

Local absorption spectra of single and coupled semiconductor quantum dots

“…In our calculations for the QD, we start from the single-particle energies e v e (e w h ) and wave functions v e (r) ( w h (r)) for electrons (holes), which we derive by solving the single-particle Schrö dinger equation within the envelope-function and effective-mass approximations [13,14]. When the semiconductor nanostructure is perturbed by an external light field (e.g.…”