Andrew studied Physics at the University of Natal and received his PhD in 1998 in lasers/optics while working at the Atomic Energy Corporation on laser-based Uranium Enrichment. From 1999 he spent several years working in a start-up, where he helped build a private laser company from humble beginnings of just a few friends, to an enterprise employing more than 70 staff. The products are now in use at blue chip institutes around the world, including Lockheed Martin (USA), BAE (UK), ENEA (Italy), NASA (USA) and Dassault (France). The company won many technology awards, attracted significant local and foreign investment, and in 2011 was purchased outright by the USA enterprise Par Systems Inc.
In 2005 Andrew decided to return to more research orientated activities and joined the CSIR National Laser Centre where he started two new research groups: first the User Facility – a set of laboratories for advancing photonics in South Africa through engagement with local universities, and later in 2007 the Mathematical Optics group. During this time Andrew pioneered the use of digital holography for the creation and detection of optical modes, resulting in many high profile journal papers, patents and commercialisation projects. In 2015 Andrew joined the University of the Witwatersrand on the Distinguished Professor programme and has started a new laboratory that focuses on Structured Light and its applications.
Andrew has served on several international conference committees and leadership panels (SPIE, OSA, IEEE), and serves on the editorial board of Optics Express and J. Optics. Andrew is an elected member of the Academy of Science of South Africa, a founding member of the Photonics Initiative of South Africa, and a Fellow of both SPIE and the OSA. Andrew and his students have won over 70 awards for outstanding contributions to science. In 2015 Andrew won the special NSTF Photonics award for his contribution to the field over the past decade.
In 2005 Andrew decided to return to more research orientated activities and joined the CSIR National Laser Centre where he started two new research groups: first the User Facility – a set of laboratories for advancing photonics in South Africa through engagement with local universities, and later in 2007 the Mathematical Optics group. During this time Andrew pioneered the use of digital holography for the creation and detection of optical modes, resulting in many high profile journal papers, patents and commercialisation projects. In 2015 Andrew joined the University of the Witwatersrand on the Distinguished Professor programme and has started a new laboratory that focuses on Structured Light and its applications.
Andrew has served on several international conference committees and leadership panels (SPIE, OSA, IEEE), and serves on the editorial board of Optics Express and J. Optics. Andrew is an elected member of the Academy of Science of South Africa, a founding member of the Photonics Initiative of South Africa, and a Fellow of both SPIE and the OSA. Andrew and his students have won over 70 awards for outstanding contributions to science. In 2015 Andrew won the special NSTF Photonics award for his contribution to the field over the past decade.
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Controlling light with subwavelength-designed metasurfaces (MSs) has allowed for the arbitrary creation of structured light by precisely engineered matter. We report on the purity and conversion efficiency of hybrid orbital angular momentum (OAM)-generating MSs. We use a recently reported method to design and fabricate meta-surfaces that exploit generalized spin-orbit coupling to produce vector OAM states with asymmetric OAM superpositions, e.g., 1 and 5, coupled to linear and circular polarization states, fractional vector OAM states with OAM values of 3.5 and 6.5, and also the common conjugate spin and OAM of ±1 as reported in previous spin-orbit coupling devices. The OAM and radial modes in the resulting beams are quantitatively studied by implementing a modal decomposition approach, establishing both purity and conversion efficiency. We find conversion efficiencies exceeding 75% and purities in excess of 95%. A phase-flattening approach reveals that the OAM purity can be very low due to the presence of undesired radial components. We characterize the effect and illustrate how to suppress the undesired radial modes.
Digital micromirror devices (DMDs) have become ubiquitous as spatial light modulators in the optics community, but ambiguity remains on how best to implement them in a laboratory environment. Here, we explicitly tackle the problem of generating high fidelity modes of structured light while maintaining optical efficiency. We present a theoretical characterization of the diffractive properties of the DMD, allowing us to motivate an alignment procedure that improves optical efficiency. We also present a set of best practice recommendations that cover aspects of DMD operation that are not immediately intuitive, these best practice recommendations ensure structured light is generated with the correct spatial profile and wavefront. We present experimental results that show efficiency improvements of up to 20%. Further, we demonstrate the creation of modes of structured light with fidelities in excess of 96%. The best practices presented here provide a pragmatic set of procedures for ensuring DMDs are used to their fullest potential.
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