Introduction
Laser beams can have orbital angular momentum (OAM), a property of the laser beam’s phase profile whereby the beam’s phase has a “spiral” quality. OAM beams have gathered interest as another way of multiplexing optical signals and increasing bandwidth in optical communications.
Generation of OAM Beams
OAM can be imparted upon a beam by passing it through a spiral phase plate (SPP). Spiral phase plates can be made of dielectric materials and integrated on the emission surface of semiconductor lasers, including VCSELs. The PDRG has pursued such integration of SPPs on VCSELs and VCSEL arrays (see “Orbital Angular Momentum Modes from Coherently Coupled VCSEL Arrays” and “Orbital Angular Momentum Modes from VCSELs using Grayscale Photolithography” in Resources).
Arrays of OAM Lasers: Beam-Steering
Coherently coupled VCSEL arrays exhibit many novel behaviors, including electrically controlled beam-steering. Integrating SPPs onto arrays of VCSELs to turn them into arrays of OAM lasers can enable novel beam modification and beam-steering, as electromagnetic simulations have shown (see “Beam-Steering in 2D via Non-Linear Mapping of 1D Beam-Steering” in Resources).
Resources
- “Orbital Angular Momentum Modes from VCSELs using Grayscale Photolithography” (DOI) (Paper)
- “Orbital Angular Momentum Modes from Coherently Coupled VCSEL Arrays” (DOI) (IEEEXplore)
- “Beam-Steering in 2D via Non-Linear Mapping of 1D Beam-Steering” (DOI) (IEEEXplore) (Abstract) (Presentation Slides)