Transport in Complex Heterogeneous Photonic Structures

Proper understanding of multiple scattering of light is essential in many areas of science and technology. The interest ranges from fundamental photonics and the quest for the elusive phenomena of Anderson localization, to atmospherical optics and climate research, to applied spectroscopy. In biomedical optics, proper account of light scattering is necessary to extract information on crucial parameters such as blood oxygenation and hemoglobin concentration. In industry, non-destructive testing of e.g. food products or pharmaceuticals involve spectroscopic measurements on materials in which light is multiply scattered. This broad interest is reflected by an enormous body of science regarding light transport in turbid media. Typically, light transport is in these areas is viewed as a random walk based on independent and exponential distributed steps, and that the diffusion constant is given by the famous relation D=1/3vE lt (where vE is the energy velocity and lt the average length of the exponential steps). This picture is appropriate for systems where scatterers are uniformly, but randomly, distributed in space. However, there are many systems in which scatterers are not uniformly distributed. An obvious example is our atmosphere, having complex cloud layers that determines our earth's solar energy balance. In recent years, such aspects of light transport are receiving increasing attention, and an area that could be referred to as anomalous transport of light has been formed. Along with the current interest in super-diffusion coming from the atmospherical optics community, the recent introduction of well-controlled heterogeneous laboratory systems with superdiffusive properties (so called Lévy glass ) has further increased the interest in this topic. However, how heterogeneous distributions of scatterers influence light transport remains poorly understood. The main aim of this thesis is to fill this gap, both experimentally and theoretically.