Comparison of theory and experiment for nonlinear transmission and differential transmission through a 20nm ZnSe layer for circular and linear light polarization (Schumacher et al., PRB 72, 081308(R) (2005)).

Four-wave-mixing signal for a 60nm GaAs layer for xy-polarization configuration of the pump and probe pulses (Schumacher et al., PRB 73, 035318 (2006)).

Nonlinear polariton propagation in the coherent regime

For optical excitation with sufficiently weak external fields, the only dynamic quantity which determines the optical properties of the semiconductor material is the excitonic transition amplitude.

To extend the theoretical description of propagation effects to the nonlinear regime, the dynamics-controlled truncation (DCT) approach is used here to truncate the infinite many-particle hierarchy in the equations of motion for the electronic system. This approach results in a systematic perturbation theory in which all relevant many-particle correlations can, without further approximation, be taken into account. In the low-intensity regime and on ultra short time scales the assumptions on which the DCT theory is based are very well fulfilled: Coherence for the electronic system which is optically excited from its ground state can almost perfectly be realized. So far, theories based on this scheme have successfully been applied to quasi two-dimensional quantum-well systems, or to one-dimensional model systems.

Our new formulation incorporates both, propagation effects and coherent third order many-particle effects on a microscopic level. It properly accounts for the finite spatial extension of the exciton and biexciton states within a spatially inhomogeneous system. The approach is based on a direct solution of the two- and four-particle Schrödinger equations for the exciton and biexciton motion together with Maxwell's equations. We apply microscopic boundary conditions to avoid ambiguities due to ABCs. Excellent agreement of our theoretical results with experimental nonlinear transmission spectra has been demonstrated for a ZnSe/ZnSSe heterostructure.

theory:

Stefan Schumacher, University of Bremen, Germany
Gerd Czycholl, University of Bremen, Germany
Frank Jahnke, University of Bremen, Germany

experiment:

Iryna Kudyk, University of Bremen, Germany
Tobias Voss, University of Bremen, Germany
Lars Wischmeier, University of Bremen, Germany
Ilja Rückmann, University of Bremen, Germany
Jürgen Gutowski, University of Bremen, Germany

Arne Gust, University of Bremen, Germany
Detlef Hommel, University of Bremen, Germany