14 Externe wissenschaftliche Einrichtungen
Permanent URI for this collectionhttps://elib.uni-stuttgart.de/handle/11682/15
Browse
1 results
Search Results
Item Open Access Microscopic spatio-temporal dynamics of semiconductor quantum well lasers and amplifiers(2007) Böhringer, Klaus; Hess, Ortwin (Prof. Dr.)This work discusses light-matter interaction and optical nonlinearities in semiconductor nanostructures and presents a detailed numerical analysis of the spatio-temporal dynamics in novel high-power diode lasers. We derive a microscopic, spatially resolved model that combines a density matrix approach to the carrier and gain dynamics in semiconductor quantum well gain media with the macroscopic Maxwell equations for the electromagnetic field dynamics. We present Maxwell semiconductor Bloch equations in full time-domain that cover many-body interactions, a diversity of time scales and gain saturation mechanisms, and comprise the fast-oscillating carrier wave and a sub-wavelength spatial resolution. Our work focuses on ultrafast carrier effects, a quantitative understanding of optical nonlinearities, the engineering of the mode structure in microcavities, and their impact on the laser emission characteristics. Optical dephasing and carrier relaxation due to the screened Coulomb interaction and scattering with phonons are explored in detail. This work aims to improve the quantitative understanding of lasing systems of technological or fundamental relevance by performing numerical experiments: Within the framework of the paraxial wave approximation, we study the excitation of multiple transverse modes, multi-mode dynamics and the occurrence of unstable optical filaments in broad area edge-emitting lasers. We analyse vertical cavity surface-emitting laser devices with a periodically structured defect as an example of a photonic band edge band gap laser. In particular, we explore the utilisation of photonic crystal structures: gain enhancement for band edge modes and the reduction of optical losses. The complex interplay between the intracavity optical field and quantum well gain dynamics is investigated for realistic optically pumped external cavity surface-emitting laser structures. We also consider the interaction of high-intensity femtosecond and picosecond pulses with semiconductor optical amplifiers and absorbers. We identify the microscopic origin of the fast nonlinearities, obtain nonlinear gain coefficients and recovery rates, and analyse the nonlinear pulse reshaping, i.e. changes and asymmetries in the amplified pulse shape and spectrum. Built upon efficient numerical algorithms and the increased availability of inexpensive high-performance computing resources, our microscopic time-domain approach is well suitable for the engineering and design optimisation of modern nanostructured high-power diode lasers.