The recently developed two-dimensional Fourier-Transform-Spectroscopy (2DFTS) in the optical regime has been established as an elegant experiment, which has manifold of applications in the investigation of semiconductor nanostructures. Here we focus on the real and imaginary part 2DFT spectra. As predicted recently, using rephasing and non-rephasing modes, we are able to determine the homogeneous and inhomogeneous broadenings of coupled excitonic resonances even for weak disorder where photon-echo data are not useful. Computed real and imaginary parts of the 2DFTS for rephasing and non-rephasing modes are compared with experimental data of a GaAs quantum well. It is demonstrated, that phase sensitive data for the rephasing and non-rephasing modes are able to accurately provide the disorder induced broadening in a complex coupled: system for each:transition separately. (C) 2009 WILEY-VCH Verlag GmbH & Co, KGaA, Weinheim

Many-body effects dominate the polarization studies of heavy- and light-hole excitons. Accurate simulations require Coulomb correlations beyond Hartree-Fock approximation. Raman coherences are isolated with a new two-dimensional projection.

In a recent publication [Phys. Rev. Lett. 97, 227402 (2006)], it has been demonstrated numerically that a long-range disorder potential in a semiconductor quantum well can be reconstructed reliably via single-photon interferometry of spontaneously emitted light. In the present paper, a simplified analytical model of independent two-level systems is presented in order to study the reconstruction procedure in more detail. With the help of this model, the measured photon correlations can be calculated analytically and the influence of parameters, such as the disorder length scale, the wavelength of the used light, or the spotsize can be investigated systematically. Furthermore, the relation between the proposed angle-resolved single-photon correlations and the disorder potential can be understood and the measured signal is expected to be closely related to the characteristic strength and length scale of the disorder.

Homogeneous and inhomogeneous broadening of heavy- and light-hole excitons in semiconductor quantum wells are measured along with the excitation dependence of both broadenings. Isolation of disorder-induced broadening is possible with spectra in different coherent pathways.

Recent experimental data on the dynamics of photoinduced volume changes in chalcogenide glasses are analyzed within a simple phenomenological model. Both kinetics of the volume expansion under continuous irradiation and that of the relaxation after the illumination is switched off are considered. Comparison between theoretical results and experimental data provides a quantitative estimate of the local conversion rate of structural units responsible for the effect into the expanded states. Furthermore, this comparison shows that the conversion rate in a-As2Se3 is several times smaller than that in a-Se.

c © 2002 by John von Neumann Institute for Computing Permission to make digital or hard copies of portions of this work for personal or classroom use is granted provided that the copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page. To copy otherwise requires prior specific permission by the publisher mentioned above.

Optical 2D Fourier transform spectroscopy (2DFTS) provides insight into the many-body interactions in direct gap semiconductors by separating the contributions to the coherent nonlinear optical response. We demonstrate these features of optical 2DFTS by studying the heavy-hole and light-hole excitonic resonances in a gallium arsenide quantum well at low temperature. Varying the polarization of the incident beams exploits selection rules to achieve further separation. Calculations using a full many-body theory agree well with experimental results and unambiguously demonstrate the dominance of many-body physics.

Photoluminescence in (GaIn)(NAs) quantum wells designed for laser emission was studied experimentally and theoretically. The observed temperature dependences of the luminescence Stokes shift and of the spectral linewidth evidence the essential role of disorder in the dynamics of the recombining excitations. The spatial and energy disorders can cause a localization of photocreated excitations supposedly in the form of excitons. Theoretical study of the exciton dynamics is performed via kinetic Monte Carlo simulations of exciton hopping and recombination in the manifold of localized states. Direct comparison between experimental spectra and theoretical calculations provides quantitative information on the energy scale of the potential fluctuations in (GaIn)(NAs) quantum wells. The results enable one to quantify the impact of annealing on the concentration of localized states and/or on the localization length of excitons in (GaIn)(NAs) quantum wells.

Absorption spectra of semiconductor structures in photonic crystal environments are investigated numerically. It is shown that the periodic dielectric structuring changes the local optical and Coulomb interaction properties of semiconductor electron–hole excitations. The structurally induced modifications offer the possibility to design important aspects of the optoelectronic semiconductor properties.

Macro- and micro-photoluminescence (PL) spectroscopy has been applied to investigate the exciton localization in cubic CdS/ZnSe type-II superlattices (SL) in the temperature range 5-35 K. The non-monotonic shift of the macro-FL peak with increasing temperature reveals the kinetic contribution of acoustic-phonon-assisted exciton multi-hopping processes. The experimental data are described by means of computer simulation and calculations based on a kinetic theory generalized from zero to finite temperatures. The advantages of each theoretical approach are discussed.

A two-band model of a disordered semiconductor is used to analyze dynamical interaction induced weakening of localization in a system that is accessible to experimental verification. The results show a dependence on the sign of the two-particle interaction and on the optical excitation energy of the Coulomb-correlated electron-hole pair.

Get PDF Email Share Share with Facebook Tweet This Post on reddit Share with LinkedIn Add to CiteULike Add to Mendeley Add to BibSonomy Get Citation Copy Citation Text Gero Von Plessen, Torsten Meier, Jochen Feldmann, Peter Thomas, Ernst O. Göbel, and Stephan W. Koch, "Intrinsic Perturbations of Bloch Oscillations and Wannier-Stark Ladders in Semiconductor Superlattices," Optics & Photonics News 5(12), 20-21 (1994) Export Citation BibTex Endnote (RIS) HTML Plain Text Citation alert Save article

The application of an electric field parallel to the growth direction of a semiconductor superlattice replaces the continuous spectrum of miniband states by a series of equally spaced levels called the Wannier-Stark ladder1. The equivalent of the Wannier-Stark ladder in the time-domain axe Bloch oscillations of the particle in the miniband, i.e. the electron periodically traverses the Brillouin zone. It has been shown theoretically that Bloch oscillations should be observable in the time domain by performing time-resolved four-wave mixing experiments.2,3