Light is a ubiquitous carrier of information. This information can be encoded in the intensity, direction, frequency and polarisation of the light and, which was described more recently, in its orbital angular momentum. Although creating light beams with orbital angular momentum is relatively easy, measuring this property has proven to be difficult. In this thesis we present two fundamental methods to solve this problem. First, we show that by analysing the interference pattern behind a multi-pinhole interferometer, we can determine the phase and amplitude of the light impinging the pinholes, making it possible to determine the orbital angular momentum of the incoming light beam. A multi-pinhole interferometer can be scaled to arbitrary sizes, making it suitable for studying optical fields that stretch out over large distances, that can be expected in, for instance, astrophysics. The second method is based on transforming the helical wave fronts that are associated with light beams with orbital angular momentum to distinguishable, titled wave fronts that can be easily sorted by a lens. This method works for single photons, making it a key piece in a high-dimensional optical communication scheme. This thesis provides theory, simulations and measurements on both detection methods.LEI Universiteit LeidenUBL - phd migration 201
