Generation and detection of bessel beams.
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Date
2015
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Abstract
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.
Description
M. Sc. University of KwaZulu-Natal, Durban 2015.
Keywords
Gaussian beams., Bessel functions., Theses -- Physics.