Browsing by Author "Majola, Nombuso."

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Digital control of light.
(2019) Majola, Nombuso.; Chetty, Naven.; Dudley, Angela.; Forbes, Andrew.
The objective of this research was to describe innovative ways in which digital holography can be applied in controlling laser light. The ability to control and manipulate a laser beam has become an extremely desirable feature since it enables improvement in the efficiency and quality of a number of applications. Methods of controlling light make use of optical components to change the properties of a light beam according to the function of that optical element; therefore, a particular arrange- ment of optical elements in a system controls light in a certain way. Technological advancements in the field of optics have developed a versatile device called a spatial light modulator (SLM), which is a novel instrument that employs computer gener- ated holographic patterns (or phase masks) to modulate the amplitude and /or phase of a laser beam and it can therefore perform the function of a number of optical elements. This research presents novel optical set-ups based on the phase-only liquid crystal spatial light modulator (LC-SLM) for generating, controlling and exploring different laser beam pat- terns. The thesis has three main sections, the first one is Holographic beam shaping, where a Gaussian beam was reshaped using an SLM to produce Vortex, Bessel or Laguerre-Gaussian beams. These beams were found to agree with theoretically generated beams. Secondly, we produce o -axis laser beams by constructing coherent superpositions of Gaussian and vortex modes and then use two measurement techniques, peak intensity ratio and modal decomposition technique, to obtain the constituent components of these fields. Finally, we investigate the propagation dynamics of Vortex and Laguerre-Gaussian beams by using a SLM to digitally propagate these beams in free space, and then perform mea- surements on the far field intensity pattern. The results show that the Laguerre-Gaussian beam suffers less spreading and beam distortion compared to the vortex beam in free space propagation.