# Publications

# 2018

### Characterization and mitigation of information loss in a six-state quantum-key-distribution protocol with spatial modes of light through turbulence

*Physical Review A*

##### Ndagano B. and Forbes A.

Quantum communication with structured photons is topical, owing to the multidimensional state space of spatial modes. However, spatial modes are fragile and their quality degrades when perturbed in traditional communication media such as free-space and optical fibers. Here, we illustrate the effects of atmospheric turbulence on a six-state quantum-key-distribution protocol with orbital angular momentum (OAM) modes… Found Here

### A vector holographic optical trap

*Scientific Reports*

##### Bhebhe N, Williams P., Rosales-Guzmán C., Rodriguez-Fajardo V., and Forbes A.

The invention of optical tweezers almost forty years ago has triggered applications spanning multiple disciplines and has also found its way into commercial products. A major breakthrough came with the invention of holographic optical tweezers (HOTs), allowing simultaneous manipulation of many particles, traditionally done with arrays of scalar beams. Here we demonstrate a vector HOT with arrays of digitally controlled Higher-Order Poincaré Sphere (HOPS) beams. We employ a simple set-up using a spatial light modulator and show… Found Here

### High-dimensional quantum channel estimation using classical light

*Physical Review A*

##### Mabena C. and Roux F. S.

A method is proposed to characterize a high-dimensional quantum channel with the aid of classical light. It uses a single nonseparable input optical field that contains correlations between spatial modes and wavelength to determine the effect of the channel on the spatial degrees of freedom. The channel estimation process incorporates spontaneous parametric up-conversion (sum frequency generation) to perform the necessary measurements. Found Here

### Diffraction-induced entanglement loss of orbital-angular-momentum states

*Physical Review A*

##### Sorelli G, Shatokhin V. N., Roux F. S., and Buchleitner A.

We provide an analytical expression for the entanglement decay of initially maximally entangled orbital-angular-momentum biphoton states, when scattered off an obstruction. We show that the decay is controlled by the diffraction-induced mutual overlap between the diffracted field modes, and quantify its dependence on the size and position of the obstruction. Found Here

### Turbulence and the Hong-Ou-Mandel effect

*Physical Review A*

##### Prabhakar S., Mabena C., Konrad T., and Roux F.S.

The effect of a decoherence channel, such as a turbulent atmosphere, on the second-order quantum interference in the Hong-Ou-Mandel (HOM) effect is investigated. The investigation includes both theoretical analyses and an experimental implementation of the process. In our experiment, entangled input states are prepared with spontaneous parametric down-conversion. The atmospheric turbulence is modeled as… Found Here

### Combining spatiotemporal and particle-number degrees of freedom

*Physical Review A*

##### Roux F. S.

Quadrature bases that incorporate spatiotemporal degrees of freedom are derived as eigenstates of momentum-dependent quadrature operators. The resulting bases are shown to be orthogonal for both the particle-number and the spatiotemporal degrees of freedom. Using functional integration, we also demonstrate the completeness of these quadrature bases. Found Here

### Recovery of nonseparability in self-healing vector Bessel beams

*Physical Review A*

##### Otte E., Nape I., Rosales-Guzmán C., Vallés A., Denz C., and Forbes A.

One of the most captivating properties of diffraction-free optical fields is their ability to reconstruct upon propagation in the presence of an obstacle, both classically and in the quantum regime. Here we demonstrate that the local entanglement, or nonseparability, between the spatial and polarization degrees of freedom also experience self-healing. We measured and quantified the degree of nonseparability between the two degrees of freedom when propagating behind various obstructions, which were generated digitally. Experimental results show that… Found Here

### A review of complex vector light fields and their applications

*Journal of Optics*

##### Rosales-Guzmán C., Ndagano B., and Forbes A.

Vector beams, and in particular vector vortex beams, have found many applications in recent times, both as classical fields and as quantum states. While much attention has focused on the creation and detection of scalar optical fields, it is only recently that vector beams have found their place in the modern laboratory. In this review, we outline the fundamental concepts of vector beams, summarise the various approaches to control them in the laboratory, and give a concise overview of the many applications they have spurned. Found Here

### Evolution of orbital angular momentum in three-dimensional structured light

*Physical Review A*

##### Dorrah A., Rosales-Guzmán C., Forbes A., and Mojahedi M.

Light beams with an azimuthal phase dependency of e^(iℓϕ) have helical phase fronts and thus carry orbital angular momentum (OAM), a strictly conserved quantity with propagation. Here we engineer quasi-three-dimensional (3D) structured light fields and demonstrate unusual scenarios in which OAM can vary locally in both sign and magnitude along the beam’s axis, in a controlled manner, under free-space propagation. To reveal the underlying mechanisms of this phenomenon, we perform full modal decomposition and reconstruction of the generated beams to describe the evolution of their intrinsic OAM and topological charge with propagation… Found Here

### Self-healing high-dimensional quantum key distribution using hybrid spin-orbit Bessel states

*Optics Express*

##### Nape I., Otte E., Vallés A., Rosales-Guzmán C., Cardano F., Denz C., and Forbes A.

Using spatial modes for quantum key distribution (QKD) has become highly topical due to their infinite dimensionality, promising high information capacity per photon. However, spatial distortions reduce the feasible secret key rates and compromise the security of a quantum channel. In an extreme form such a distortion might be a physical obstacle, impeding line-of-sight for free-space channels. Here, by controlling the radial degree of freedom of a photon’s spatial mode, we are able to demonstrate hybrid… Found here

### Modal Diversity for Robust Free-Space Optical Communications

*Physical Review Applied*

##### Cox M., Cheng L., Rosales-Guzmán C., and Forbes A.

Free-space communication links are severely affected by atmospheric turbulence, which causes degradation in the transmitted signal. One of the most common solutions to overcome this is to exploit diversity. In this approach, information is sent in parallel over different paths using two or more transmitters that are spatially separated, with each beam therefore experiencing different atmospheric turbulence, lowering the probability of a receive error. In this work we propose and experimentally demonstrate a alternative method of diversity based on spatial modes of light, which we call modal diversity. We remove the need for a physical separation of the transmitters by exploiting the fact that spatial modes of light experience… Found Here

### Brightness enhancement in a solid-state laser by mode transformation

*Optica*

##### Naidoo D., Litvin A. I. and Forbes A.

Laser brightness is a measure of the ability to deliver intense light to a target and encapsulates both the energy content and the beam quality. High-brightness lasers require that both parameters be maximized, yet standard laser cavities do not allow this. For example, multimode beams, a mix of many transverse modes, have a high energy content but low beam quality, while single transverse mode Gaussian beams have a good beam quality, but their small mode volume means a low energy extraction. Here we overcome this fundamental limitation and demonstrate an optimal approach to realizing high-brightness lasers. We employ… Found Here

### A compact diffractive sorter for high-resolution demultiplexing of orbital angular momentum beams

*Scientific Reports*

##### Ruffato G., Girardi M., Massari M,. Mafakheri E., Sephton B., Capaldo P., Forbes A. and Romanato F.

The design and fabrication of a compact diffractive optical element is presented for the sorting of beams carrying orbital angular momentum (OAM) of light. The sorter combines a conformal mapping transformation with an optical fan-out, performing demultiplexing with unprecedented levels of miniaturization and OAM resolution. Moreover, an innovative configuration is proposed which simplifies alignment procedures and further improves the compactness of the optical device. Samples have been fabricated in the form of phase-only diffractive optics… Found Here

### The first iteration of Grover’s algorithm using classical light with orbital angular momentum

*Journal of Modern Optics*

##### Perez-Garcia B., Hernandez-Aranda I. R., Forbes, A and Konrad T.

We present an experimental realization of the first iteration in Grover’s quantum algorithm using classical light and linear optical elements. The algorithm serves to find an entry marked by an oracle in an unstructured database. In our scheme, the quantum states encoding the database are represented by helical modes generated by means of a Spatial Light Modulator, while the marking corresponds to a π phase shift of the hidden mode. The optical implementation of Grover’s algorithm then selectively amplifies the intensity of the marked mode such that it can be revealed by a modal decomposition. The core of the algorithm… Found Here

### Classical and quantum analysis of propagation invariant vector flat-top beams

*Applied Optics*

##### Bhebhe N., Rosales-Guzman C. and Forbes A.

Laser beams with a near uniform intensity profile, such as flat-top and super-Gaussian beams, have found many applications, particularly in laser materials processing. Unfortunately such beams are not eigenmodes of free space and, thus, alter their intensity profile during propagation. This may be overcome by creating vector flat-top beams. Here, we exploit the polarization dependent efficiency of spatial light modulators to create a vector flat-top beam that maintains its intensity profile and vector nature during propagation. We apply a holistic classical and quantum toolkit to analyze the dynamics of the vector state during propagation and demonstrate the versatility of these beams in an optical trapping and tweezing application. Found Here

### Are Bessel beams resilient to aberrations and turbulence?

*Journal of the Optical Society of America*

##### Mphuti, N., Botha, R. and Forbes, A.

It is understood from the conical wave picture that Bessel beams may self-heal after certain opaque obstructions, but the extrapolation to transparent phase screens is not self-evident. Here we consider the propagation of Bessel beams through aberrated obstacles and show that the self-healing is not guaranteed, but rather a function of the severity of the aberration. Paradoxically, we explain why strong aberrations may show self-healing while weak aberrations will not… Found Here

### Tackling Africa’s digital divide

*Nature Photonics*

##### Lavery, M., Abadi, M., Bauer, R., Brambilla, G., Cheng, L., Cox, M., Dudley, A., Ellis, A., Fontaine, N., Kelly, A., Marquardt, C., Matlhane, S., Ndagano, B., Petruccione, F., Slavík, R., Romanato, F., Rosales-Guzmán, C., Roux, F., Roux, K., Wang, J. and Forbes, A.

Innovations in ‘sustainable’ photonics technologies such as free-space optical links and solar-powered equipment provide developing countries with new cost-effective opportunities for deploying future-proof telecommunication networks…. Found Here

### Purity of vector vortex beams through a birefringent amplifier

*Physical Review Applied*

##### Sroor, H., Nyameko, L., Naidoo, D., Litvin, I., and Forbes, A.

Creating high-quality vector vortex (VV) beams is possible with a myriad of techniques at low power, and while a few studies have produced such beams at high power, none have considered the impact of amplification on the vector purity. Here we employ tools to study the amplification of VV beams and, in particular, the purity of such modes. We outline a versatile toolbox for such investigations and demonstrate its use in the general case of VV beams through a birefringent gain medium. Intriguingly, we show that it is possible to enhance the purity… Found Here

### Entanglement beating in free space through spin-orbit coupling

*Light: Science & Application*

##### Otte, E., Rosales-Guzman, C., Ndagano, B., Denz, C., and Forbes, A.

It is well known that the entanglement of a quantum state is invariant under localunitary transformations. This rule dictates, for example, that the entanglement of internal degrees of freedom of a photon remain invariant during free-space propagation. Here, we outline a scenario in which this paradigm does not hold. Using local Bell states engineered from classical vector vortex beams with non-separable degrees of freedom, so-called classically entangled states, we demonstrate that the entanglement evolves during propagation, oscillating between maximally entangled (purely vector) and product states (purely scalar). We outline… Found Here

### Turbulence and the Hong-Ou-Mandel effect

*Physical Review A*

##### Prabhakar, S., Mabena, C., Konrad, K., and Roux, F.

The effect of a decoherence channel, such as a turbulent atmosphere, on the second order quantum interference in the Hong-Ou-Mandel (HOM) effect is investigated. The investigation includes both theoretical analyses and an experimental implementation of the process. In our experiment, entangled input states are prepared with spontaneous parametric down-conversion. The atmospheric turbulence is modelled as a single-phase screen and… Found Here

### Structured Laguerre-Gaussian beams for mitigation of spherical aberration in tightly focused regimes

*Journal of Optics*

##### Haddadi, S., Bouzid, O., Fromager, M., Hasnaoui, A., Harfouche, A., Cagniot, E., Forbes, A., and Ait-Ameur, K.

Many laser applications utilise a focused laser beam having a single-lobed intensity profile in the focal plane, ideally with the highest possible on-axis intensity. Conventionally, this is achieved with the lowest-order Laguerre–Gaussian mode (LG00), the Gaussian beam, in a tight focusing configuration. However, tight focusing often involves significant spherical aberration due to the high numerical aperture of the systems involved, thus degrading the focal quality. Here, we demonstrate that a high-order radial LGp0 mode can be tailored to meet and in some instancesexceed the performance of the Gaussian. We achieve… Found Here

### Creation and detection of vector vortex modes for classical and quantum communication

*Journal of Lightwave Technology*

##### Ndagano, B., Nape, I.,Cox M., Rosales-Guzmán C. and Forbes, A.

Vector vortex beams are structured states of light that are nonseparable in their polarisation and spatial mode, they are eigenmodes of free-space and many fiber systems, and have the capacity to be used as information carriers for both classical and quantum communication. Here, we outline recent progress in our understanding of these modes, from their creation to their characterization and detection. We then use these tools to study their propagation behavior in free-space and optical fiber and show that modal cross-talk results in a decay of vector states into separable scalar modes, with a concomitant loss of information. We present… Found Here

### A hybrid quantum eraser scheme for characterization of free-space and fiber communication channels

*Optics Communications*

##### Nape, I., Kyeremah, C., Vallés, A., Rosales-Guzmán, C., Buah-Bassuah, P., and Forbes, A.

We demonstrate a simple projective measurement based on the quantum eraser concept that can be used to characterize the disturbances of any communication channel. Quantum erasers are commonly implemented as spatially separated path interferometric schemes. Here we exploit the advantages of redefining the which-path information in terms of spatial modes, replacing physical paths with abstract paths of orbital angular momentum (OAM). Remarkably, vector modes (natural modes of free-space and fiber) have a non-separable feature of spin–orbit coupled states, equivalent to the description of two independently marked paths. We explore… Found Here

##### 2017

*Scientific reports**,**7**(1), 13882. Download*Bouzid O., Haddadi, S., Fromager, M., Cagniot, E., Ferria, K., Forber, A. and Ait-Ameur, K. (2017). Focusing anomalies with binary diffractive optical elements, *Applied Optics 56, 9735.*

Mabena, C. and Roux, F. (2017). High-dimensional quantum channel estimation using classical light, *Phys. Rev. A . 96, 053860. Download*

Ndagano, B., Mphuthi, N., Milione, G. and Forbes, A. (2017). Comparing mode-crosstalk and mode-dependent loss of laterally displaced orbital angular momentum and Hermite–Gaussian modes for free-space optical communication. *Optics letters , 42(20), 4175-4178. Download*

Rosales-Guzmán, C., Bhebhe, N. and Forbes, A. (2017). Simultaneous generation of multiple vector beams on a single SLM. *Optics express , 25(21), 25697-25706. Download*

Zhang, Y., Agnew, M., Roger, T., Roux, F.S., Konrad, T., Faccio, D., Leach, J. and Forbes, A. (2017). Simultaneous entanglement swapping of multiple orbital angular momentum states of light. *Nature Communications , 8(1), 632. Download*

Vetter, C., Dudley, A., Szameit, A. and Forbes, A. (2017). Real and virtual propagation dynamics of angular accelerating white light beams. * Optics express , 25(17), 20530-20540. Download*

Rosales-Guzmán, C. and Forbes, A. (2017). How to shape light with spatial light modulators. SPIE.SPOTLIGHT Download

Forbes, A. and Botha, L., (2017). Laser Isotope Separation. Laser Beam Shaping Applications (2nd ed.), *Ch. 7*, eds. F.M. Dickey and T. Lizotte. CRC Taylor & Francis Group (New York) Download

Rosales-Guzmán, C., Bhebhe, N., Mahonisi, N. and Forbes, A. (2017). Multiplexing 200 modes on a single digital hologram. *Journal of Optics*, 19 113501 Download

Nape, I., Kyeremah, C., Vallés, A., Rosales-Guzmán, C., Buah-Bassuah, P.K. and Forbes, A., (2017). Hybrid quantum erasure scheme for channel disturbance characterization. *Optics Communications* 408, 53-57 Download

Roux F.S. (2017). Biphoton states in correlated turbulence, *Phys. Rev. A.*Download

Nape, I., Ndagano, B. and Forbes, A., (2017). Erasing the orbital angular momentum information of a photon. *Physical Review A*, *95* (5), 053859 Download

Ismail, Y., Joshi, S., Forbes, A. and Petruccione, F., (2017). Instrumentation limitation on a polarization-based entangled photon source. *JOSA B*, *34*(6), 1084-1089 Download

McLaren, M. and Forbes, A., (2017). Digital spiral-slit for bi-photon imaging. *Journal of Optics*, *19*(4), 044006 Download

Webster, J., Rosales-Guzmán, C. and Forbes, A., (2017). Radially dependent angular acceleration of twisted light. *Optics letters*, *42*(4), 675-678. Download

Ndagano, B., Perez-Garcia, B., Roux, F.S., McLaren, M., Rosales-Guzman, C., Zhang, Y., Mouane, O., Hernandez-Aranda, R.I., Konrad, T. and Forbes, A., (2017). Characterizing quantum channels with non-separable states of classical light. *Nature Physics*, *13*(4), 397 Download

Forbes, A., (2017). Controlling light’s helicity at the source: orbital angular momentum states from lasers. *Phil. Trans. R. Soc. A*, *375*(2087), 20150436 Download

Sephton, B., Dudley, A. and Forbes, A. (2017). Quantum Walks. *Quest*, *13*(4), 15-18. Download

Forbes, A. (2017). Blurring the classical quantum divide. *Optics and photonics news*, *17*(12), 36. Download

Rubinsztein-Dunlop, H., Forbes, A., Berry, M., Dennis, M., Andrews, D., Mansuripur, M., Denz, C., Alpmann, C., Banzer, P., Bauer, T. and Karimi, E., (2016). Roadmap on structured light. *Journal of Optics*, *19*(1), 013001. Download

##### 2016

*Journal of Optics*,

*18*(5), 054005. download

Roux, F. S. (2016). Non-Markovian evolution of photonic quantum states in atmospheric turbulence. *Journal of Optics*, *18*(5), 055203. download

Zhang, Y., Prabhakar, S., Rosales-Guzmán, C., Roux, F. S., Karimi, E., & Forbes, A. (2016). Hong-Ou-Mandel interference of entangled Hermite-Gauss modes. *Physical Review A*, *94*(3), 033855. download

Zhang, Y., Prabhakar, S., Roux, F. S., Forbes, A., & Konrad, T. (2016). Experimentally observed decay of high-dimensional entanglement through turbulence. *Physical Review A*, *94*(3), 032310. download

Sephton, B., Dudley, A., & Forbes, A. (2016). Revealing the radial modes in vortex beams. *Applied optics*, *55*(28), 7830-7835. download

Cox, M. A., Rosales-Guzmán, C., Lavery, M. P., Versfeld, D. J., & Forbes, A. (2016). On the resilience of scalar and vector vortex modes in turbulence. *Optics express*, *24*(16), 18105-18113. download

Perez-Garcia, B., Yepiz, A., Hernandez-Aranda, R. I., Forbes, A., & Swartzlander, G. A. (2016). Digital generation of partially coherent vortex beams. *Optics Letters*, *41*(15), 3471-3474. download

Ndagano, B., Sroor, H., McLaren, M., Rosales-Guzmán, C., & Forbes, A. (2016). Beam quality measure for vector beams. *Optics Letters*, *41*(15), 3407-3410. download

Trichili, A., Salem, A. B., Dudley, A., Zghal, M., & Forbes, A. (2016). Encoding information using Laguerre Gaussian modes over free space turbulence media. *Optics Letters*, *41*(13), 3086-3089. download

Gossman, D., Perez-Garcia, B., Hernandez-Aranda, R. I., & Forbes, A. (2016). Optical interference with digital holograms. *American Journal of Physics*, *84*(7), 508-516. download

Trichili, A., Rosales-Guzmán, C., Dudley, A., Ndagano, B., Salem, A. B., Zghal, M., & Forbes, A. (2016). Optical communication beyond orbital angular momentum. *Scientific reports*, *6*. download

Forbes, A., Dudley, A., & McLaren, M. (2016). Creation and detection of optical modes with spatial light modulators. *Advances in Optics and Photonics*, *8*(2), 200-227. download

Perez-Garcia, B., McLaren, M., Goyal, S. K., Hernandez-Aranda, R. I., Forbes, A., & Konrad, T. (2016). Quantum computation with classical light: Implementation of the Deutsch–Jozsa algorithm. *Physics Letters A*, *380*(22), 1925-1931. download

Naidoo, D., Roux, F. S., Dudley, A., Litvin, I., Piccirillo, B., Marrucci, L., & Forbes, A. (2016). Controlled generation of higher-order Poincaré sphere beams from a laser. *Nature Photonics*, *10*(5), 327-332. download

Goyal, S. K., Roux, F. S., Konrad, T., & Forbes, A. (2016). The effect of turbulence on entanglement-based free-space quantum key distribution with photonic orbital angular momentum. *Journal of Optics*, *18*(6), 064002. download

Naidoo, D., Harfouche, A., Fromager, M., Ait-Ameur, K., & Forbes, A. (2016). Emission of a propagation invariant flat-top beam from a microchip laser. *Journal of Luminescence*, *170*, 750-754. download

Zhang, Y., Roux, F. S., Konrad, T., Agnew, M., Leach, J., & Forbes, A. (2016). Engineering two-photon high-dimensional states through quantum interference. *Science advances*, *2*(2), e1501165. download

Brüning, R., Ndagano, B., McLaren, M., Schröter, S., Kobelke, J., Duparré, M., & Forbes, A. (2016). Data transmission with twisted light through a free-space to fiber optical communication link. *Journal of Optics*, *18*(3), 03LT01. download

Dudley, A., Majola, N., Chetty, N., & Forbes, A. (2016). Implementing digital holograms to create and measure complex-plane optical fields. *American Journal of Physics*, *84*(2), 106-112. download

##### 2015

Naidoo, D., Fromager, M., Ait-Ameur, K., & Forbes, A. (2015). Radially polarized cylindrical vector beams from a monolithic microchip laser. *Optical Engineering*, *54*(11), 111304-111304. download

Brüning, R., Flamm, D., Ngcobo, S. S., Forbes, A., & Duparré, M. (2015, February). Rapid measurement of the fiber’s transmission matrix. In *SPIE OPTO* (pp. 93890N-93890N). International Society for Optics and Photonics. download

Goyal, S. K., Roux, F. S., Forbes, A., & Konrad, T. (2015). Implementation of multidimensional quantum walks using linear optics and classical light.*Physical Review A*, *92*(4), 040302. download

Brüning, R., Zhang, Y., McLaren, M., Duparré, M., & Forbes, A. (2015). Overlap relation between free-space Laguerre Gaussian modes and step-index fiber modes. *JOSA A*, *32*(9), 1678-1682. download

McLaren, M., Konrad, T., & Forbes, A. (2015). Measuring the nonseparability of vector vortex beams. *Physical Review A*, *92*(2), 023833. download

Litvin, I. A., Mhlanga, T., & Forbes, A. (2015). Digital generation of shape-invariant Bessel-like beams. *Optics express*, *23*(6), 7312-7319. download

Schulze, C., Roux, F. S., Dudley, A., Rop, R., Duparré, M., & Forbes, A. (2015). Accelerated rotation with orbital angular momentum modes. *Physical Review A*, *91*(4), 043821. download

Ndagano, B., Bruning, R., McLaren, M., Duparre, M., & Forbes, A. (2015) Fiber propagation of vector modes. *Optics Express*, 23(13), 17330-17336. download

Perez-Garcia, B., Francis, J., McLaren, M., Hernandez-Aranda, R. I., Forbes, A., & Konrad, T. (2015). Quantum computation with classical light: The Deutsch Algorithm. *Physics Letters A*, *379*(28), 1675-1680. download

Litvin, I. A., Mhlanga, T., & Forbes, A. (2015). Digital generation of shape-invariant Bessel-like beams. *Optics express*, *23*(6), 7312-7319. download

McLaren, M. G., Roux, F. S., & Forbes, A. (2015). Realising high-dimensional quantum entanglement with orbital angular momentum. *South African Journal of Science*, *111*(1-2), 01-09. download

Burger, L., Litvin, I., Ngcobo, S., & Forbes, A. (2015). Implementation of a spatial light modulator for intracavity beam shaping. *Journal of Optics*, *17*(1), 015604. download

Milione, G., Dudley, A., Nguyen, T. A., Chakraborty, O., Karimi, E., Forbes, A., & Alfano, R. R. (2015). Measuring the self-healing of the spatially inhomogeneous states of polarization of vector Bessel beams. *Journal of Optics*, *17*(3), 035617. download

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##### 2014

Aspden, R.S. et al., 2014. Experimental demonstration of Klyshko’s advanced-wave picture using a coincidence-count based, camera-enabled imaging system. *Journal of Modern Optics*, 61(March), pp.1–5. doi: 10.1080/09500340.2014.899645 download

Ismail, Y. et al., 2014. Characterization of a Polarisation Based Entangled Photon Source. *The African Review of Physics*, 9, pp.217–226.download

Litvin, I. a et al., 2014. Doughnut laser beam as an incoherent superposition of two petal beams. *Optics letters*, 39(3), pp.704–7. doi: 10.1364/OL.39.000704. download

Schulze, C. et al., 2014. Measurement of the orbital angular momentum density of Bessel beams by projection into a Laguerre-Gaussian basis. *Applied optics*, 53(August), pp.5924 – 5933. doi: 10.1364/AO.53.005924. download

Spangenberg, D.-M. et al., 2014. White light wavefront control with a spatial light modulator. *Optics Express*, 22(11), p.13870. doi: 10.1364/OE.22.013870.download

Trichili, A., Mhlanga, T. & Ismail, Y., 2014. Detection of Bessel beams with digital axicons. *Optics Express*, 22(14), pp.17553 – 17560. doi: 10.1364/OE.22.017553.download

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##### 2013

Boubaha, B. et al., 2013. Spatial properties of coaxial superposition of two coherent Gaussian beams. *Applied optics*, 52(23), pp.5766–72. doi: 10.1364/AO.52.005766. download

Chaibi, A., Mafusire, C. & Forbes, A., 2013. Propagation of orbital angular momentum carrying beams through a perturbing medium. *Journal of Optics*, 15(10), p.105706. doi: 10.1088/2040-8978/15/10/105706. download

Giovannini, D. et al., 2013. Characterization of high-dimensional entangled systems via mutually unbiased measurements. *Physical Review Letters*, 110(14), pp.1–5. doi: 10.1103/PhysRevLett.110.143601.download

Goyal, S.K. et al., 2013. Implementing quantum walks using orbital angular momentum of classical light. *Physical Review Letters*, 110(26), pp.1–5. doi: 10.1103/PhysRevLett.110.263602. download

Litvin, I. a, Burger, L. & Forbes, A., 2013. Angular self-reconstruction of petal-like beams. *Optics letters*, 38(17), pp.3363–5. doi: 10.1364/OL.38.003363. download

Schulze, C. et al., 2013a. Measurement of the orbital angular momentum density of light by modal decomposition. *New Journal of Physics*, 15(July), p.073025. doi: 10.1088/1367-2630/15/7/073025 download

Schulze, C. et al., 2013b. Reconstruction of laser beam wavefronts based on mode analysis. *Applied optics*, 52(21), pp.5312–7. doi: 10.1364/AO.52.005312.download

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##### 2012

Dudley, A. & Forbes, A., 2012. From stationary annular rings to rotating Bessel beams. *Journal of the Optical Society of America A*, 29(4), p.567. doi: 10.1364/JOSAA.29.000567.download

Flamm, D. et al., 2012. Mode analysis with a spatial light modulator as a correlation filter. *Optics Letters*, 37(13), p.2478. doi: 10.1364/OL.37.002478. download

Ismail, Y. et al., 2012. Shape invariant higher-order Bessel-like beams carrying orbital angular momentum. *Journal of Optics*, 14(8), p.085703. doi: 10.1088/2040-8978/14/8/085703. download

Litvin, I. a. et al., 2012. Azimuthal decomposition with digital holograms. *Optics Express*, 20(10), p.10996. doi: 10.1364/OE.20.010996. download

Naidoo, D. et al., 2012. Observing mode propagation inside a laser cavity. *New Journal of Physics*, 14(May), p.053021. doi: 10.1088/1367-2630/14/5/053021. download

Schulze, C., Flamm, D., et al., 2012. Beam-quality measurements using a spatial light modulator. *Optics Letters*, 37(22), pp.4687–9. doi: 10.1364/OL.37.002478.Decomp_Schulze2012 (1)

Schulze, C., Ngcobo, S., et al., 2012. Modal decomposition without a priori scale information. *Optics Express*, 20(25), pp.27866–73. doi: 10.1364/OE.20.027866.download

Schulze, C., Naidoo, D., et al., 2012. Wavefront reconstruction by modal decomposition. *Optics Express*, 20(18), p.19714. doi: 10.1364/OE.20.019714.Decomposition_Schulze2012

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##### 2011

Agnew, M. et al., 2011. Tomography of the quantum state of photons entangled in high dimensions. *Physical Review A – Atomic, Molecular, and Optical Physics*, 84(6), p.062101. doi: 10.1103/PhysRevA.84.062101.

Godin, T. et al., 2011. Transverse correlation vanishing due to phase aberrations. *Optics Communications*, 284(19), pp.4601–4606. doi: 10.1016/j.optcom.2011.05.062.

Lavery, M.P.J. et al., 2011. Robust interferometer for the routing of light beams carrying orbital angular momentum. *New Journal of Physics*, 13(September), p.093014. doi: 10.1088/1367-2630/13/9/093014.

Litvin, I. a., Dudley, A. & Forbes, A., 2011. Poynting vector and orbital angular momentum density of superpositions of Bessel beams. *Optics Express*, 19(18), p.16760. doi: 10.1364/OE.19.016760.

McLaren, M., Sidderas-Haddad, E. & Forbes, A., 2011. Accurate measurement of microscopic forces and torques using optical tweezers. *South African Journal of Science*, 107(9-10), pp.1–8. doi: 10.4102/sajs.v107i9/10.579.

Naidoo, D. et al., 2011. Transverse mode selection in a monolithic microchip laser. *Optics Communications*, 284(23), pp.5475–5479. doi: 10.1016/j.optcom.2011.08.017.

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##### 2010 & older

Bernhardi, E.H. et al., 2008. Estimation of thermal fracture limits in quasi-continuous-wave end-pumped lasers through a time-dependent analytical model. *Optics Express*, 16(15), pp.11115–11123. doi: 10.1364/OE.16.011115.

Burger, L. & Forbes, A., 2008. Kaleidoscope modes in large aperture Porro prism resonators. *Optics Express*, 16(17), pp.12707–12714. doi: 10.1364/OE.16.012707.

Litvin, I. A. & Forbes, A., 2009. Gaussian mode selection with intracavity diffractive optics. *Optics Letters*, 34(19), pp.2991–2993. doi: 10.1364/OL.34.002991.

Litvin, I. A. & Forbes, A., 2008. Bessel-Gauss resonator with internal amplitude filter. *Optics Communications*, 281(9), pp.2385–2392. doi: 10.1016/j.optcom.2007.12.052.

Litvin, I.A. & Forbes, A., 2009. Intra – cavity flat – top beam generation. *Optics Express*, 17(18), pp.15891–15903. doi: 10.1364/OE.17.015891.

Mafusire, C. et al., 2008. Optical aberrations in a spinning pipe gas lens. *Optics Express*, 16(13), pp.9850–9856. doi: 10.1364/OE.16.009850.

Vasilyeu, R. et al., 2009. Generating superpositions of higher-order Bessel beams. *Optics Express*, 17(26), pp.23389–23395. doi: 10.1364/OE.17.023389.

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