  Harnessing the Orbital Angular Momentum (OAM) of light is an appealing
approach to developing photonic technologies for future applications in optical
communications and high- dimensional Quantum Key Distributions (QKD). An
outstanding challenge to the widespread uptake of the OAM resource is its
efficient generation. We design a new device which can directly emit an
OAM-carrying light beam. By fabricating micro-scale Spiral Phase Plates (SPPs)
within the aperture of a Vertical-Cavity Surface-Emitting Laser (VCSELs), the
linearly polarized Gaussian beam emitted by the VCSEL is converted into a beam
carrying specific OAM modes and their superposition states with high efficiency
and high beam quality. The innovative OAM emitter opens a new horizon in the
field of OAM-based optical and quantum communications, especially for short
reach data interconnects and Quantum Key Distribution (QKD).

Optics