Optical vortices and vortex beams

Light may carry angular momentum in two forms: spin angular momentum and orbital angular momentum (OAM). While the former has been understood for some time, and is simply the polarisation of the light, the latter is a topic of current interest. There has been renewed interest in solutions to the Helmholtz equation that carry OAM, such as Bessel, Bessel-Gauss, and Laguerre-Gauss beams. OAM carrying fields have distinct phase singularities which give rise to intensity nulls. Such beams are generally referred to as optical vortices or vortex beams, and can be used as an “optical spanner” to rotate everything from solid particles to living cells. An emerging research field is the OAM state of single photons, and the use of OAM states for two-photon entanglement in OAM. This is the domain of paraxial quantum optics.

Our research focuses on the study of laser beams that carry OAM, and the application of these beams to optical trapping and tweezing, and photon entanglement through OAM states for testing hypothesis in quantum information and quantum cryptography. Particular emphasis will be placed on the generation of vortices of various order, and the measurement of these vortices as they propagate through turbulent and non-linear media. The study of general fields with multiple optical vortices will also be undertaken to understand the creation and annihilation of vortices during propagation. This is important for the correction of scintillated beams after propagation through the atmosphere.

Other projects: