Identifying orbital angular momentum of light in quantum wells

Recently, the generation and detection of structured light have been the subject of intense studies, aiming to realize high-capacity optical storage and continuous-variable quantum technologies. In this Letter, we present a scheme to extract the orbital angular momentum content of vortex beams, possessing integer and fractional azimuthal index, in GaAs/AlGaAs multiple quantum wells with a double-Lambda type configuration. Arising from a quantum interference term, the absorption of a non-vortex probe field depends upon the azimuthal phase of vortex fields so that both the magnitude and sign of azimuthal index/indices can be mapped into the absorption profile.