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Browsing Conference Publications by Author "Naidoo, Darryl"

Now showing items 1-20 of 20

Amplification of higher-order Poincaré sphere beams

Author: Naidoo, Darryl ; Sroor, H ; Litvin, I ; Forbes, A Date: Sep 2019 The Higher order Poincar´e sphere (HOPS) is generally used to describe scalar and vector orbital angular momentum modes. These modes have found many applications to date; however, they are limited to low power levels. It has thus become topical ... Read more
Characterising laser beams with liquid crystal displays

Author: Dudley, Angela L ; Naidoo, Darryl ; Forbes, A Date: Sep 2016 We show how one can determine the various properties of light, from the modal content of laser beams to decoding the information stored in optical fields carrying orbital angular momentum, by performing a modal decomposition. Although the ... Read more
Demonstrating optical aberrations in the laboratory

Author: Naidoo, Darryl ; Mafusire, C ; Forbes, A Date: Jul 2009 An optical aberration is a distortion of an image as compared to the object due to defects in an optical system Read more
Detecting defects during powder deposition in additive manufacturing

Author: Hendriks, Adriaan J ; Ramokolo, Lesiba R ; Ngobeni, Christopher M ; Moroko, Matome C ; Naidoo, Darryl Date: Nov 2018 Additive manufacturing applications, in areas such as aerospace and medicine, are limited due to the lack of process stability and quality management. In particular, geometrical inaccuracies and the presence of mechanical defects hinder ... Read more
Digital holograms for laser mode multiplexing

Author: Mhlanga, T ; Trichili, A ; Dudley, Angela L ; Naidoo, Darryl ; Zghal, M ; Forbes, A Date: 02 Oct 2014 High-capacity data transmission has been implemented using single channel optical systems. This technique is limited and soon it will be unable to ful ll the growing needs for higher bit rate data transmission. Hence multi-mode transmission ... Read more
The generation of flat-top beams by complex amplitude modulation with a phase-only spatial light modulator

Author: Hendriks, A ; Naidoo, Darryl ; Roux, FS ; Löpez-Mariscal, C ; Forbes, A Date: Aug 2012 Phase-only spatial light modulators are now ubiquitous tools in modern optics laboratories, and are often used to generate so-called structured light. In this work we outline the use of a phase-only spatial light modulator to achieve full ... Read more
Generation of shape-invariant flat-top laser beams

Author: Ait-Ameur, K ; Naidoo, Darryl ; Ngcobo, Sandile ; Fromager, M ; Litvin, I ; Hasnaoui, A ; Harfouche, A ; Forbes, A Date: Feb 2015 A great number of laser applications need in place of the usual Gaussian beam a flat-top intensity profile in the focal plane of a focusing lens. In general the transformation of the laser beam from the Gaussian to the flat-top shape is made ... Read more
Improving the laser brightness of a commercial laser system

Author: Naidoo, Darryl ; Litvin, Ihar ; Forbes, A Date: Feb 2017 We investigate the selection of a flat-top beam and a Gaussian beam inside a laser cavity on opposing mirrors. The concept is tested external to the laser cavity in a single pass and double pass regime where the latter mimics a single round ... Read more
Intra-cavity decomposition of a dual-directional laser beam

Author: Naidoo, Darryl ; Forbes, A ; Aït-Ameur, K ; Fromager, M Date: Jan 2011 A method of decomposing a dual-directional laser beam into a forward propagating field and a backward propagating field for an apertured plano-concave cavity is presented. An intra-cavity aperture is a simple method of laser beam shaping as ... Read more
Intra-cavity metamorphosis of a Gaussian beam to flat-top distribution

Author: Naidoo, Darryl ; Litvin, I ; Laskin, A ; Forbes, A Date: Feb 2014 We explore an intra-cavity beam shaping approach to generate a Gaussian distribution by the metamorphosis of a Gaussian beam into a flat-top distribution on opposing mirrors. The concept is tested external to the cavity through the use of two ... Read more
Intra-cavity vortex beam generation

Author: Naidoo, Darryl ; Aït-Ameur, K ; Forbes, A Date: Aug 2011 In this paper the authors explore vortex beams and in particular the generation of single LG0l modes and superpositions thereof. Vortex beams carry orbital angular momentum (OAM) and this intrinsic property makes them prevalent in transferring ... Read more
Laguerre Gaussian beam multiplexing through turbulence

Author: Trichili, A ; Mhlanga, T ; Naidoo, Darryl ; Dudely, A ; Zghal, M ; Forbes, A Date: 17 Aug 2014 We analyze the effect of atmospheric turbulence on the propagation of multiplexed Laguerre Gaussian modes. We present a method to multiplex Laguerre Gaussian modes using digital holograms and decompose the resulting field after encountering ... Read more
Layer-wise powder deposition defect detection in additive manufacturing

Author: Hendriks, Adriaan J ; Ramokolo, Lesiba R ; Ngobeni, Christopher M ; Moroko, Matome C ; Naidoo, Darryl Date: Mar 2019 Additive manufacturing applications, in areas such as aerospace and medicine, are limited due to the lack of process stability and quality management. In particular, geometrical inaccuracies and the presence of mechanical defects hinder ... Read more
A novel laser resonator for fractal modes

Author: Sroor, H ; Naidoo, Darryl ; Courtial, J ; Forbes, A Date: Feb 2018 Mathematical self-similar fractals manifest identical replicated patterns at every scale. Recently, fractals have found their way into a myriad of applications. In optics, it has been shown that manipulation of unstable resonator parameters ... Read more
Scalar and vector vortex beams from the source

Author: Naidoo, Darryl ; Roux, FS ; Dubery, Angela L ; Litvin, Ihar ; Piccirillo, B Date: Oct 2016 We introduce a laser for generating all states on the Higher-order Poincaré sphere by coupling spin angular momentum to orbital angular momentum and we demonstrate that the OAM degeneracy of a laser may be broken. Read more
Spatial superpositions of Gaussian beams

Author: Naidoo, Darryl ; Godin, T ; Fromager, M ; Aït-Ameur, K ; Forbes, A Date: Feb 2014 We explore an interferometric beam shaping technique that considers the coaxial superposition of two Gaussian beams. This technique is traditionally implemented in a Mach-Zehnder interferometer; however, to avoid phase shift drift due to ... Read more
Thermal lensing measurement from the coefficient of defocus aberration

Author: Bell, Teboho ; Forbes, A ; Ngcobo, Sandile ; Naidoo, Darryl Date: Mar 2016 We measured the thermally induced lens from the coefficient of defocus aberration using a Shack-Hartmann wavefront sensor (SHWFS). As a calibration technique, we infer the focal length of standard lenses probed by a collimated Gaussian beam ... Read more
Thermally induced lensing determination from the coefficient of defocus aberration

Author: Bell, Teboho ; Naidoo, Darryl ; Forbes, Andrew Date: Jul 2014 The effects of a temperature gradient in a laser crystal in an end-pumped configuration in a solid-state laser resonator results in thermally induced aberrations. Of particular interest we measure the thermally induced lens from the coefficient ... Read more
Unraveling light with digital holograms

Author: Forbes, A ; Schulze, C ; Ngcobo, Sandile ; Flamm, D ; Naidoo, Darryl ; Dudley, Angela L ; Duparre, M Date: Feb 2013 Modal decomposition of optical fields as a concept has been in existence for many decades, yet despite its clear applications to laser beam analysis it has nevertheless remained a seldom used tool. With the commercialization of liquid crystal ... Read more
The Wigner distribution function in modal characterisation

Author: Mredlana, Prince ; Naidoo, Darryl ; Mafusire, C ; Kruger, T ; Dudley, Angela L ; Forbes, A Date: Jul 2016 Optical field characterisation often requires various isolated experiments to obtain characterisation parameters, we investigate a novel approach to characterise an optical field employing a Wigner distribution function with a modal decomposition ... Read more

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