Discrete emitters as a source of orbital angular momentum

作者:Liu R*; Phillips D B; Li F; Williams M D; Andrews D L; Padgett M J
来源:Journal of Optics, 2015, 17(4): 045608.
DOI:10.1088/2040-8978/17/4/045608

摘要

Generation of light carrying orbital angular momentum (OAM) is of fundamental interest due to its applications in a broad range of fields, such as classical and quantum optical communications, and optical micro-manipulation. Light carrying a well defined state of OAM is typically created by imparting an azimuthally varying phase structure onto a plane wave. In this work, we investigate, using numerical simulations and experiments, the OAM spectra of light radiated from a heavily course grained emission pattern: an array of discrete circular apertures arranged in a ring configuration, with a constant phase increment between adjacent apertures. We show how the number of apertures and their relative phase defines the position and spacing of peaks in the OAM spectra. We demonstrate that by spatially filtering beams emitted from such a configuration, higher order peaks in the OAM spectra can be suppressed, leaving a single dominant lowest order peak, and recovering a beam carrying a well-defined OAM state. We qualitatively interpret the efficiency of generating beams this way in terms of the angular uncertainty principle.