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Browsing by Subject "Optics"

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Anomalous transient behavior from an inhomogeneous initial optical vortex density

Author: Roux, FS Date: Apr 2011 Inhomogeneous optical vortex densities can be produced in stochastic optical fields by a combination of coherent and incoherent superposition of speckle fields. During subsequent propagation, the inhomogeneity in the vortex density decays ... Read more
Azimuthal decomposition of optical modes

Author: Dudley, Angela L ; Litvin, I ; Roux, FS ; Forbes, A Date: Jul 2012 This presentation analyses the azimuthal decomposition of optical modes. Decomposition of azimuthal modes need two steps, namely generation and decomposition. An azimuthally-varying phase (bounded by a ring-slit) placed in the spatial frequency ... Read more
Computational fluid dynamics model of the spinning pipe gas lens

Author: Mafusire, C ; Forbes, A ; Snedden, Glen C Date: Aug 2010 When a metal horizontal pipe is heated and spun along its axis, a graded refractive index distribution is generated which is can be used as a lens, thus its name, the spinning pipe gas lens (SPGL). Previous experimental results of its performance ... Read more
Coupled optical resonance laser locking

Author: Burd, CC ; Du Toit, PJW ; Uys, H Date: Oct 2014 We have demonstrated simultaneous laser frequency stabilization of a UV and IR laser, to coupled transitions of ions in the same spectroscopic sample, by detecting only the absorption of the UV laser. Separate signals for locking the different ... 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
Digitally controlling the ‘twist’ of light

Author: Dudley, Angela L ; Forbes, A Date: May 2014 This study reports on the presentation of the second international conference on applications of optics and photonics: Digitally controlling the ‘twist’ of light. Read more
Estimating uncertainty in resolution tests

Author: Goncalves, DP ; Griffith, DJ Date: May 2006 Resolution testing of imaging optical equipment is still commonly performed using the USAF 1951 target. The limiting resolution is normally calculated from the group and element that can just be resolved by an observer. Although resolution ... Read more
Evaluation of WC-9Co-4Cr laser surface alloyed coatings on stainless steel

Author: Obadele, A ; Olubambi, PA ; Pityana, Sisa L ; Popoola, API Date: Jul 2011 In order to examine the microstructure and hardness behaviour of WC cermets, coatings have been obtained by laser surface alloying technique. WC-9Co-4Cr particulate was injected onto the surface of AISI 304L austenitic stainless steel (ASS) ... Read more
Experimental generation and application of the superposition of higher-order Bessel beams

Author: Dudley, Angela L ; Vasilyeu, R ; Forbes, A ; Khilo, N ; Ropot, P Date: Jul 2009 This presentation provides information on experimental generation and application of the superposition of higher-order Bessel beams. The superposition of zero order Bessel beams can be used to measure the radius of curvature of a reflecting ... Read more
Fabrication of selective solar absorbers using pulsed laser deposition

Author: Yalisi, B ; Katumba, G ; Forbes, A ; Pillay, SR Date: Jun 2009 Selective solar absorbers are devices that have been designed to absorb as much as possible of the solar radiation which is in the wavelength range of 0.3 to 2.5 µm and to minimise thermal emittance in the wavelength range from 2.5µm to the ... Read more
From stationary annular rings to rotating Bessel beams

Author: Dudley, Angela L ; Forbes, A Date: Apr 2012 In this work we use a phase-only spatial light modulator (SLM) to mimic a ring-slit aperture, containing multiple azimuthally varying phases at different radial positions. The optical Fourier transform of such an aperture is currently known ... Read more
Generating superpositions of higher order bessel beams [Conference paper]

Author: Vasilyeu, R ; Dudley, Angela L ; Khilo, N ; Forbes, A Date: Oct 2009 An experimental setup to generate a superposition of higher-order Bessel beams by means of a spatial light modulator and ring aperture is presented. The experimentally produced fields are in good agreement with those calculated theoretically. Read more
Generating superpositions of higher–order Bessel beams [Journal article]

Author: Vasilyeu, R ; Dudley, Angela L ; Khilo, N ; Forbes, A Date: Dec 2009 The authors report the first experimental generation of the superposition of higher-order Bessel beams, by means of a spatial light modulator (SLM) and a ring slit aperture. They present illuminating a ring slit aperture with light which has ... Read more
Ho:YLF & Ho:LuLF slab amplifier system delivering 200 mJ, 2 µm single-frequency pulses

Author: Strauss, Hencharl J ; Koen, W ; Bollig, C ; Esser, MJD ; Jacobs, Cobus ; Collett, OJP ; Preussler, DR Date: Jul 2011 A single-frequency single-pass amplifier based on Ho:YLF and Ho:LuLF in a scalable slab architecture delivering up to 210 mJ at 2064 nm is demonstrated. The amplifier was end-pumped by a 1890 nm Tm:YLF slab laser and was seeded with a 69 mJ ... Read more
How to distinguish between the annihilation and the creation of optical vortices

Author: Roux, FS Date: Oct 2013 Optical vortices are always created or annihilated as vortex dipoles — pairs with opposite topological charge. Here a quantity, consisting of the transverse first and second derivatives of the optical field, is derived with which one can ... Read more
Implementation of intra-cavity beam shaping technique to enhance pump efficiency

Author: Litvin, IA Date: Feb 2012 In this work the author proposes an implementation of a new intra-cavity beam shaping technique to vary the intensity distribution of the fundamental mode in a resonator cavity while maintaining a constant intensity distribution at the output. ... Read more
Implementation schemes for unsharp measurements with trapped ions

Author: Choudhary, SK ; Konrad, T ; Uys, H Date: Jan 2013 Unsharp positive operator-valued measurements allow a variety of measurement applications which minimally disrupt the state of the quantum system. Experimental schemes are proposed for implementing unsharp measurements on the qubit levels of ... 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
Laser alloying of AI with mixed Ni, Ti and SiC powders

Author: Mabhali, Luyolo AB ; Pityana, Sisa L ; Sacks, N Date: Mar 2010 Laser alloying of aluminium AA1200 was performed with a 4.4kW Rofin Sinar Nd:YAG laser to improve the surface hardness. Alloying was carried out by depositing Ni, Ti and SiC powders of different weight ratios on the aluminum substrate. The ... Read more
Laser cladding of aluminium using TiB2

Author: Kumar, S ; Pityana, Sisa L Date: Mar 2010 Modification of Aluminium surface by injecting, dispersing and melting TiB2 powder with the help of a laser beam promises to enhance tribological properties of Aluminium. The present work consists of making single lines and various overlapping ... Read more

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Browsing by Subject "Optics"

Browsing by Subject "Optics"

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