Popular Abstract in English Imagine a solar powered flash light. Each photon absorbed by the flash light’s solar cell creates electric energy and the flash light’s light source converts the electrical energy again into photons. The purpose of such a device may be questionable, because you would be surprised if it would create more light than what it absorbs. However, under certain conditions it isIn this thesis the luminescence properties of highly doped semiconductors are studied with focus on degenerately n-doped InP. It is demonstrated how photoluminescence measurements on degenerately doped semiconductors allow an estimation of the doping concentration without need for electrical contacts. The degenerate doping can furthermore reveal the conduction band structure for energies higher th

Isotropic chiral media can be modeled in several ways. We show that when realizing such a medium from spiral inclusions with real permittivities and permeabilities in a periodic structure, a modified Drude-Born-Fedorov model is obtained. This model equals the original Born model for small wave vectors, but the strength of the chirality depends on the propagation direction. The effective parameters

Self-adaptation enables software to execute successfully in dynamic, unpredictable, and uncertain environments. Control theory provides a broad set of mathematically grounded techniques for adapting the behavior of dynamic systems. While it has been applied to specific software control problems, it has proved difficult to define methodologies allowing non-experts to systematically apply control te

In the future, both rising sea water level and higher precipitation are expected due to climate change. Gothenburg is one of the cities in Sweden most affected by flooding in urban areas. Flooding is caused by very high sea level, but also as a consequence of heavy rainfall over the city. It is unknown whether high sea level or heavy rainfall is the most important reason for flooding, or if the co

Scattering not only broadens the width of the optical transition between two levels but can enable optical gain and absorption to coexist — a fact that is unambiguously demonstrated by the observation of 'Bloch gain' in a quantum cascade laser.

Heat release in the end-gas prior to autoignition was investigated using different experimental methods including transducers for heat flux and pressure as well as rotational coherent anti-Stokes-Raman spectroscopy, which is a laser-based method for non-intrusive instantaneous thermometry of the gas. The time history was examined in the cases of mixtures of various stoichio-metries, where some wer

The high time resolution of ultra-wideband (UWB) signals results in a large number of multipath components (MPCs) arriving at the receiver, which presents a source of diversity. In addition to this multipath diversity, there is also repetition diversity inherent in impulse radio (IR) UWB systems, since a number of pulses are transmitted for each information symbol. In order to make optimal use of