Study of the propagation and detection of the orbital angular momentum of light for astrophysical applications

The aim of this work is to study the propagation of orbital angular momentum (OAM) of light for astrophysical applications and a method for OAM detection with optical telescopes. The thesis deals with the study of the orbital angular momentum (OAM) as a new observable for astronomers, which could give additional information with respect to those already inferred from the analysis of the intensity, frequency and polarization of light. Indeed, the main purpose of this work is to highlight that light can have a much more complex structure, and therefore can transport much more information. In particular, firstly we show that OAM can be imparted to light from interstellar media with a perturbed electron density function in the plane perpendicular to the propagation direction, revealing that the study of OAM could give information about the spatial structures of the traversed inhomogeneous media. The second part of the thesis deals with an experimental verification of the preservation of orbital angular momentum even for uncorrelated non-monochromatic wave beams, showing that this observable of light is preserved, thus we can aim at detecting it. Finally, if OAM can transport information, and if it is preserved in propagation, the obvious consequence is the study of its detection, in particular by an OAM mode sorter fitted to optical telescopes