Abstract

The propagation of light through an ultracold atomic gas is the main topic of the present work. The thesis consists of two parts. In Part I (Chapters 1,2,3), we give a complete description of the 1D photonic bands of a MI of two-level atoms paying attention to both band diagrams and reflectivity spectra. The role of regular periodicity of the system is addressed within a polariton formalism. The scattering on defects inside lattices of three-level atoms is also studied in view of optical detection of impurities in such structures. The light is used as a probe of systems engineered by the use of other laser beams. Part II (Chapters 4,5) is devoted to the development of a general framework for the time-dependent processing of a propagating slow Dark Polariton in a spatially inhomogeneous system. The coherently tunable atomic gas acts as a Dynamic Photonic Structure. Applications of this concept concerning wavelength conversion and reshaping of the pulse are also discussed for realistic experimental situations.