Coherent propagation of polaritons in the nonlinear optical regime

Abstract

The propagation of light pulses through semiconductor heterostructures is studied under the combined influence of polariton effects and optical nonlinearities. For the investigated heterostructures, the light field strongly interacts with the excitonic resonances of the material which leads to a series of polariton resonances. Even in the linear optical regime, the theoretical description is distinctly complicated by the presence of surfaces and interfaces which prevents an analytical solution of the polariton problem. In the coherent nonlinear regime, dynamical changes of the polariton resonances and contributions of biexcitons will be addressed. For this purpose, we combine a microscopic treatment of the boundary problem for the optical interband excitations and the propagating light field in a sample of finite thickness with a description of excitonic and biexcitonic nonlinearities. A practicable scheme is developed to provide a self-consistent solution of generalized Schr\"odinger and Heitler-London equations for the excitonic and biexcitonic excitations, respectively, together with Maxwell's equations under strict consideration of the boundary conditions. To study the influence of excitonic and biexcitonic nonlinearities on single-pulse propagation, pump and probe transmission experiments, and four-wave mixing spectra, the dependence of the results on the light polarization is analyzed.