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Browsing by Author "Forbes, A"

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  • Dudley, Angela L; Majola, N; Chetty, N; Forbes, A (SPIE, 2014-09-25)
    In this work we construct coherent superpositions of Gaussian and vortex modes which can be described to occupy the complex-plane. We demonstrate how these fields can be experimentally constructed in a digital, controllable ...
  • Dudley, Angela L; Mhlanga, T; McDonald, A; Roux, FS; Lavery, M; Padgett, M; Forbes, A (SPIE Proceedings, 2013-09)
    In this work we will present two techniques for the measurement of superimposed higher-order Bessel beams. In the first technique we will outline a simple approach using only a spatial light modulator and a Fourier ...
  • Masina, BN; Mwakikunga, BW; Elayaperumal, M; Forbes, A; Bodkin, R (2011-07)
    At present it is known that diamond tool degrades with time as it is normally used at high temperatures. One of the question the authors like to answer in this study is whether thermally induced problems in diamond tool ...
  • Masina, BN; Mwakikunga, B; Forbes, A (SPIE Digital library, 2013-04)
    We outline an all-optical and noncontact approach for controlled laser heating and measurement of the resultant temperature distribution at the surface of a material, respectively. We show how the boundary conditions of ...
  • Masina, BN; Forbes, A; Ndwandwe, OM; Hearne, G; Mwakikunga, BW (2009-03)
    In this study the authors make use of laser heating of HTHP industrial diamond, as well as the optically measured temperature profile of the diamond surface, to study temperature induced changes to the diamond structure, ...
  • Bernhardi, EH; Forbes, A; Bollig, C; Esser, MJD (2008)
    One of the main problems that limit the power scaling of diode-end-pumped solid-state lasers is the generation of heat inside the laser gain medium which can ultimately cause fracture. In this paper a time-dependent ...
  • Godin, T; Forbes, A; Naidoo, Darryl; Fromager, M; Cagniot, E; Aït-Ameur, K (Elsevier, 2011-06)
    The concept of transverse correlation vanishing, between the fraction of power contained in the centre and wings of a probe beam, recently introduced [Opt. Commun. 282 (2009) 3854–3858] is important to be considered when ...
  • Naidoo, Darryl; Godin, T; Fromager, M; Cagniot, E; Passilly, N; Forbes, A; Aït-Ameur, K (Elsevier, 2011-11)
    The article outlines an approach to mode selection in a microchip laser through judicious shaping of the pump light to create a high modal overlap with the desired mode. The authors demonstrate the principle by creating a ...
  • Ngcobo, S; Ait-Ameur, K; Litvin, I; Hasnaoui, A; Forbes, A (Optical Society of America, 2013-09)
    We outline a simple laser cavity comprising an opaque ring and a circular aperture that is capable of producing spatially tuneable laser modes, from a Gaussian beam to a Flat-top beam. The tuneability is achieved by varying ...
  • Ngcobo, S; Ait-Ameur, K; Litvin, I; Hasnaoui, A; Forbes, A (SPIE Proceedings, 2014-02)
    In this paper we experimentally demonstrate a simple laser cavity that produces spatial tuneable laser modes from a Gaussian beam to a Flat-top beam and a Donut-beam. The laser cavity contains an opaque ring and an adjustable ...
  • Forbes, A; Dudley, Angela L; Roux, S (EE Publishers, 2010-12)
    Research at the Mathematical Optics Group uses "twisted" light to study new quatum-based information security systems. In order to understand the structure of "twisted" light, it is useful to start with an ordinary light ...
  • McLaren, M; Romero, J; Padgett, MJ; Roux, FS; Forbes, A (American Physical Society, 2013-09)
    In this paper we consider geometrical two-photon optics of Bessel-Gaussian modes generated in spontaneous parametric down-conversion of a Gaussian pump beam. We provide a general theoretical expression for the orbital ...
  • Forbes, A; Schulze, C; Ngcobo, S; Flamm, D; Naidoo, Darryl; Dudley, Angela L; Duparre, M (SPIE Proceedings, 2013-02)
    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 ...
  • Mhlanga, T; Dudley, Angela L; Lavery, M; Padgett, M; Forbes, A (2013-07)
    This study reports on the presentation of the 59th South African Institute of Physics Conference Unravelling Bessel beams.
  • Mafusire, C; Forbes, A; Michaelis, MM; Snedden, Glen C (2009-06)
    The graded index (GRIN-like) medium generated by a gas inside a heated pipe when it is rotated about its longitudinal axis has the ability to focus a laser beam. However, recent research has shown that the medium generated ...
  • Schulze, C; Naidoo, Darryl; Flamm, D; Schmidt, OA; Forbes, A; Duparr, M (Optical Society of America, 2012-08)
    We propose a new method to determine the wavefront of a laser beam based on modal decomposition by computer-generated holograms. The hologram is encoded with a transmission function suitable for measuring the amplitudes ...
  • Dudley, Angela L; Milione, G; Alfano, RR; Forbes, A (SPIE, 2014-09-25)
    A long-standing question in optics has been to efficiently measure the phase (or wavefront) of an optical field. This has led to numerous publications and commercial devices such as phase shift interferometry, wavefront ...
  • Forbes, A; Du Plessis, A; Rohwer, EG (2006-07)
    Wavelength tuneability is demonstrated both experimentally and numerically. Refractive element shows some anomalies, intensity correctly reproduced, but not phase. Future work will consider impact of beta on performance of designs
  • Degama, MP; Forbes, A (Society of Photo-optical Instrumentation Engineers (SPIE), 2010-07)
    This paper presents a beam shaping device namely, a Diffractive Optical Element (DOE), which is used to change a beam having a Gaussian intensity profile into a beam with a uniform intensity profile. The DOE used in this ...
  • Spangenberg, D-M; Dudley, Angela L; Neethling, PH; Rohwer, EG; Forbes, A (Optical Society of America, 2014)
    Spatial light modulators are ubiquitous tools for wavefront control and laser beam shaping but have traditionally been used with monochromatic sources due to the inherent wavelength dependence of the calibration process ...