Generation and detection of bessel beams.
Mhlanga, Thandeka. T
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In this dissertation we study the properties of Bessel-Gauss beams. Bessel-Gauss beams are created by the interference of plane waves lying on a cone, and have unique properties: they propagate without spreading and recover their phase and amplitude upon encountering an obstruction. These modes have found application in the manipulation of micro-particles, atomic dipole traps, and atomic guiding. As high-order Bessel-Gauss beams carry orbital angular momentum, they have been used as a basis for information encoding in both the classical and quantum regimes. We show how to generate these modes using axicons, and spiral ring-slits, which we implement digitally on a spatial light modulator. Using an all digital experimental setup we extract the information encoded in these modes in two dimensions, where we simultaneously detect the radial and azimuthal components of these beams. This detection tool is shown to be useful in studying Bessel-Gauss modes that have propagated through optical turbulence and that have been obstructed. Vector Bessel-Gauss beams are then generated and detected using a q-plate and polarized grating, respectively. We then apply the reconstruction property of the Bessel-Gauss modes in a quantum experimental setup, where we show that we can recover quantum entanglement after encountering an obstruction. We show that the digital spiral ring-slit can be used at the single photon level as a single pixel detector, to recover the phase and amplitude on an object in a ghost imaging setup.