Polariton Propagation and Coherent Many-Particle Effects in Semiconductor Heterostructures

Within the last few decades, semiconductor optics has attracted considerable attention due to its many applications ranging from semiconductor lasers to single photon emitting devices. The proper theoretical description of a propagating light field which is coupled to the excitonic resonances of the semiconductor material has been a longstanding problem. It is complicated by the presence of surfaces and interfaces in semiconductor heterostructures which prevents an analytical solution of the resulting polariton problem. A microscopic formulation of the coupled light and matter dynamics is required that includes the influence of sample boundaries on the electronic system as well as on the optical fields. In a regime where the optical spectra are strongly influenced by propagation effects, a theoretical description of the polariton problem is formulated. A direct solution of the non-local excitonic dynamics together with Maxwell´s equations yields a microscopic description of propagating light fields in heterostructures with a finite spatial extension.Theoretical results are discussed for the linear optical regime and a direct theory-experiment comparison is presented. Optical transmission spectra are analyzed for a series of high quality ZnSe/ZnSSe heterostructures with different thicknesses of the ZnSe layers. The theoretical results are in excellent agreement with the measurements, giving a deeper understanding of polariton propagation in shallow-confinement heterostructures.To achieve the microscopic description of propagation effects in the nonlinear optical regime the dynamics-controlled truncation formalism is applied. The complicated interplay of propagation effects and optically induced many-particle correlations is analyzed for the samples. In order to confirm the important theoretical observations, nonlinear transmission experiments have been initiated and performed. Excellent agreement with the theoretical results has been achieved.