Conveners
Photonics: Photonics in Biology
- Pieter Neethling (Laser Research Institute, University of Stellenbosch)
Photonics: Spectroscopy and imaging
- Gurthwin Bosman (Stellenbosch University)
Photonics: Quantum photonics
- Andrew Forbes (U. Witwatersrand)
Photonics: Technology and communication
- Christine Steenkamp (University of Stellenbosch)
Photonics: Beam shaping and manipulation
- Mitchell Cox (University of the Witwatersrand)
Photonics
- There are no conveners in this block
Photonics
- There are no conveners in this block
Introduction: Cervical cancer (CC) is the fourth most diagnosed cancer in women worldwide. Conventional treatments include surgery, chemo- and radio- therapy, however these are often invasive and cause severe side effects. Additionally, approximately 70% of late-stage CC patients experience metastasis due to treatment resistance and limitations. There is thus a dire need to investigate...
Melanoma is the most dangerous skin cancer and is inherently chemoresistant; thus, alternative theranostic strategies are needed for its management. Immunotherapy involves the use of antibody technology to target cancer-associated-antigens; photodynamic therapy (PDT) involves the irradiation of a photosensitiser to generate cytotoxic levels of singlet oxygen and reactive oxidative species; and...
Oesophageal cancer is an aggressive and lethal malignancy accounting for the eighth leading cause of cancer and sixth cause of cancer-related death globally. Conventional treatments for oesophageal cancer are characterised by suboptimal efficiency resulting in treatment resistance and relapse. Photodynamic therapy (PDT), a non-invasive modality, has emerged as a potential alternative cancer...
Uncontrolled diabetes mellitus (DM) increases reactive oxygen species (ROS) and oxidative stress. Oxidative stress provoke apoptosis, a programmed cell death which typically sustains the developmental mechanism for normal body homeostasis. Oxidative damage affects the expression of pro-apoptotic proteins and anti-apoptotic proteins including caspases and B cell lymphoma 2 (Bcl-2). Uncontrolled...
Abstract. Wound healing is a complex and dynamic process that involves restoring damaged tissue structure and function. Delayed wound healing often advances to chronic non-healing wounds due to reduced cellular proliferation and migration. Photobiomodulation (PBM) involves the application of low-powered light typically in the visible red and near-infrared (NIR) spectrum to modulate cellular...
Diabetes Mellitus (DM) remains a global challenge to public health and is associated with a delay in wound healing, in part due to increased oxidative stress and pro-inflammatory cytokines. Photobiomodulation (PBM) induces wound healing through diminishing inflammation and oxidative stress and has been used for the successful healing of diabetic ulcers in vivo. This study investigated the...
Pure isotopes of zinc find application in the production of radiopharmaceuticals for medical diagnostic scans (68-Zn and 67-Zn). Enrichment processes relying on mass differences do not produce products of sufficient purity for medical applications, therefore resonance laser ionisation is a potential final step in the purification process.
An experimental setup for resonance laser ionisation...
A new system for measurement of spectral power responsivity of detectors, utilising a monochromator system, was implemented at NMISA and characterised. The monochromator system includes sources of optical radiation, input optics, order sorting filters, a scanning double monochromator, diffraction gratings and output optics. As part of the characterisation, wavelength calibrations were...
Using optical tweezers, we trap microscopic polystyrene beads suspended in water and determine their diameter using Mie scattering theory. Using a near infrared laser, the optical trap is formed near the focus by a high numerical aperture lens. The particles have a higher refractive index than the surrounding medium and the focused light creates a strong gradient force which traps the...
Fourier Ptychographic Microscopy (FPM) is an imaging technique that can be used to obtain high-resolution, large field of view images of a sample. The technique is based on acquiring a number of low-resolution, large field of view images and combining them to produce one high-resolution, large field of view image of the sample. This relatively new technique was first described in 2013 .
Its...
Quantum ghost imaging is an alternative imaging technique which utilises pairs of entangled photons to reconstruct an image. Information from either one of the photons alone does not allow for image reconstruction, rather the image is reconstructed by using the correlations that exist between the photon pair. Interestingly, these photon pairs can be either degenerate or non-degenerate in...
We present a relatively unexplored direction for analogue quantum simulation based on the interaction between light and neutral atom ensembles at room temperature. The phenomenon of electromagnetically induced transparency (EIT) changes the properties of light interacting with an atomic media coherently. One result is the creation of collective excitations known as dark-state polaritons...
Skyrmions are a class of stable quasi-particles with non-trivial topological structures categorized by integer invariants called skyrme numbers. In terms of field configurations, a skyrmion is formed by the twisting of field lines into links between said field lines where the stability originates from the energy requirement to form or break any of these linkages. It is this topological...
By exploiting entanglement as a resource, information can be conveyed between two destinations with quantum teleportation. Here, the non-locality between an entangled pair of entities allows one to transmit information by employing the entangled pair as a channel between two destinations. Indirect (Bell) measurements, between one of the entangled entities and a state one desires to transmit...
A non-perturbative quantum plasmonics study of the geometry-dependent light scattering by a metamolecule weakly-driven by a plane-polarized electric field is presented. The metamolecule consists of a CdSe semiconductor quantum dot coupled to a gold nanoparticle. We show that at the Fano-dip, the delay time where scattered photons are antibunched diminishes as the nanoparticle geometry is tuned...
Path entanglement is an essential tool with regards to quantum information and communication protocols. We shall discuss the generation and measurement of path entangled photon states using pairs of single photons initially generated by Spontaneous Parametric Down-Conversion (SPDC). Path entanglement is generated through the use of a Mach-Zender (MZ) interferometer in one arm of the SPDC...
Abstract: Thermography is a non-destructive evaluation tool to measure
the amount of infrared energy emitted by an object. This energy depends
on temperature and wavelength and is described by Planck's law. From the
solution of the wave equation the k-dependent photon energies and their
density of states are calculated. The equation of state and a statistical
description of the photon gas...
We report the simulation of ultrafast pulse evolution along the silicon germanium waveguide. Pulse evolutions of 205 fs duration and 2.35 kW peak power at 4.15 μm propagating along a 7 cm long silicon germanium on silicon air-clad waveguide were simulated by solving the generalised nonlinear Schrödinger equation using the fourth order Runge Kutta in the interaction picture method. Coherent...
Orbital angular momentum (OAM) modes are topical due to their versatility, and they have been used in several applications including free-space optical communication systems. The classification of OAM modes is a common requirement, and there are several methods available for this. One such method makes use of deep learning, specifically convolutional neural networks, which distinguishes...
One of the main effects of turbulence on higher order modes used within Free Space Optical systems is crosstalk between neighbouring modes, which in turn causes Mode Dependent Loss (MDL) and generally reduces the capacity of communication systems using multiplexing. Nevertheless, crosstalk could also be used for “energy conservation” within a system. This so-called mode diversity could help...
The classical concurrence (i.e. non-separability) of vector beams has the intriguing property that it is invariant to general unitary transformations, most notably pure phase aberrations such as those induced by propagation through atmospheric turbulence. Free space communication using structured light aims to increase data transmission rates by encoding simultaneous signals in...
Light can have spin angular momentum (SAM) and orbital angular momentum (OAM). While spin angular momentum is related to circular polarization and can only be either ℏ or −ℏ, OAM is related to the vortex phase structure and is equal to lℏ where l is the number of screw dislocations in the phase profile (or topological charge). In paraxial wave optics these two physical properties are regarded...
Deformable Mirrors are highly topical due to their ability to compensate for phase distortions caused by atmospheric turbulence. Since these devices can handle optical powers in the order of kilowatts, they are well suited for high-power applications ranging from high bandwidth optical communication to spatial profile control in additive manufacturing and other applications that involve high...
Passing a beam through an aberrated optical system can result in unwanted changes to both the
phase and amplitude of the beam. These changes can greatly degrade many important properties
of the beam such as the resolution, spot size in focusing and the beam quality factor. These
aberrations are generally corrected for using pre- or post-corrective optics or other methods. The
ideal...
Laser beams structured with a uniform flattop profile have become a topic of interest in
industrial fields such high-power beam delivery directly to the point of contact for laser cutting,
welding and additive manufacturing. These applications require fibre delivery of the optical
mode to the point of contact. Here, we generate and tailor a flattop profile using a spatial light...
The appeal of beam shaping and wavefront control for coherent broadband sources has always been imbedded within the idea that the techniques and or devices implored to accomplish this, could allow one to modulate any wavelength of light using a single optical device. In recent years phase-only devices such as spatial light modulators (SLMs) have been explored to modulate and control the...
The serendipitous discovery and tremendous success of cisplatin paved way for the design and applications of transition metal-based anticancer agents. Likewise, another breakthrough in cancer treatment has been the introduction of photodynamic therapy, which uses a photosensitizer to generate reactive oxygen species and kill cancer cells. Recently, research has been focused on combining these...
Abstract: Effectiveness of anticancer therapies like chemotherapy and radiotherapy is primarily limited by development of multidrug resistant cancer cells, leading to enhanced progression, invasiveness and tumour metastasis with poor clinical outcome. Clinical findings suggest that employing mechanistically distinct therapies can overcome the resistance induced by another treatment....
Long distance optical communication has been dominated by the use of single mode optical fibres. These fibres can only accept one mode of structured light thus limiting the rate and which information can be sent and received. Conversely, free space propagation can make use of multiple modes which open up additional degrees of freedom to store information thus making information transfer...