Conveners
Photonics: Photonic Quantum Technologies & Quantum Optics
- Angela Dudley
Photonics: Photonic Quantum Technologies & Quantum Optics
- Isaac Nape (University of the Witwatersrand)
Photonics: Optical Communications & Neural Networks
- Gurthwin Bosman (Stellenbosch University)
Photonics: Structured Light, OAM & Topology
- Pieter Neethling (Stellenbosch University)
Photonics: Biosensing & Diagnostics with Photonics
- Christine Steenkamp (University of Stellenbosch)
Photonics: Laser Characterisation & Spectroscopy
- Tjaart Krรผger (University of Pretoria)
Photonics: Photobiomodulation & Biomedical Applications
- Mitchell Cox (University of the Witwatersrand, Joahnnesburg)
Photonics: Photosynthesis & Biophysics
- Saturnin Ombinda-Lemboumba (Council for Scientific and Industrial Research (CSIR),)
Photonics: Biophotonics & PDT-Cancer Therapy
- ANDREW FORBES (U. Witwatersrand)
Photonics: Biophotonics & PDT-Cancer Therapy
- Angela Dudley
Photonics: Biophotonics & PDT-Cancer Therapy
- Isaac Nape (University of the Witwatersrand)
Photonics
- Angela Dudley
Quantum sensing leverages the distinct characteristics of quantum states to surpass classical measurement precision limits. We propose a theoretical study which provides a comparative analysis of various entangled quantum states, specifically NOON states, twisted NOON states, entangled coherent states, and BAT states, for advanced sensing applications. We evaluate each state's phase estimation...
Trapped ions are promising candidates to use as qubits in quantum computers, offering long coherence times, scalability, and precise control of the states of each ion individually by means of lasers. The long-term goal of this quantum control project is to achieve unsharp measurements with two isotopes of ytterbium, Yb-171 and Yb-174, in a linear Paul trap. To predict and interpret...
Metal nanoparticles have been shown to be good mediators for entanglement generation in plasmonically-coupled quantum dot qubits. These mediators enable entanglement to be sustained over long qubit-qubit distances. We investigate the impact of the number of mediating particles on the generation of bipartite entanglement by considering both parallel and perpendicular nanoarrays with respect to...
Non-local entangled states are an important resource for future quantum technologies, but their practical use is hindered by the effects of noisy quantum channels. However, recently discovered quantum Skyrmions, topologically structured entangled states, offer a promising solution. In this work, we develop a theoretical framework to study the evolution of entangled states and their topology in...
Tailoring lightโs degrees of freedom and coupling them to enable complex transformations has become topical, with applications spanning high-dimensional information processing to advanced imaging systems at both classical and quantum levels. In this work, we introduce a voltage-controlled, multiwavelength spinโorbit coupling approach to engineer the entanglement properties of photon pairs...
In this work, we investigate the quantum light emission properties of single nitrogen-vacancy (NV) centres in diamond under continuous-wave (CW) excitation at a wavelength 532 nm while the emitted photons have a wavelength of 637 nm. Using Hanbury Brown and Twiss (HBT) interferometry, we measure the second-order correlation function (gยฒ(ฯ)) to characterize the photon statistics of the...
Revealing the quantum nature of a source that generally is considered classic radiation is significant. In quantum optics and generally in optics we have the scalability problem as the experiment extends. Hence, finding sources that can overcome this challenge is essential. Radiation from a continuous wave (CW) source is described by the dynamics of quasi-classical (coherent) states. Such a...
Quantum ghost imaging offers an interesting approach to imaging, harnessing entangled photon pairs to capture images using photons that never directly interact with the object. Traditionally, this technique relies on costly single-photon cameras or pixelated projective masks, where image resolution is fundamentally limited by the pixel size of the detectors or masks. We propose a shift from...
The utilisation of mode division multiplexing, where multiple spatial modes transmit data simultaneously, holds significant promise for enhancing bandwidth in free space optical communication systems. However, atmospheric turbulence can compromise the reliability of these systems. To address this longstanding problem, traditional neural networks have been employed to classify modes in...
The Faraday Effect, a magneto-optic phenomenon, causes the rotation of linearly polarised light when subjected to a magnetic field along the direction of propagation. In magneto-optic materials like multimode fibres, where different spatial modes interfere to form complex speckle patterns, could these modes be influenced by applying an external transverse magnetic field to the multimode fibre?...
Physical perturbations (bends) in optical fibre cause mode-mixing: energy coupling and interference between the fibre's (otherwise propagation invariant) eigenmodes. This mode-mixing can be described using a complex transmission matrix (TM). The ability to predict the effect of physical bends on the TM can help improve mode division multiplexing, imaging, and endoscopy; furthermore, it enables...
LaguerreโGaussian (LG) modes are solutions of the paraxial Helmholtz equation in cylindrical coordinates and are associated with light fields carrying orbital angular momentum (OAM). It is customary to modulate such beams using phase-only vortex profiles, e.g. when increasing (laddering up) or decreasing (laddering down) the OAM content of some given LG mode. However, the resulting beams have...
Structured light, tailored in its degrees of freedom for specific applications, has recently emerged as a highly topical field driven by advancements in both linear and nonlinear optical techniques. This has led to significant progress in nonlinear structured light, with applications spanning holography, spectroscopy, imaging, and even quantum teleportation. These breakthroughs rely on the...
The ability to tailor light in all of its degrees of freedom has seen significant improvements in the fields of optical imaging and communications. It has allowed for the straightforward implementation of spatial modes of light which can be used to form higher dimensional encoding alphabets to increase the bandwidths of free space and optical fibre channels. The orthogonality and completeness...
The topology of light and its robustness to noise has garnered significant interest over the last few years as a promising means of information transfer. Lightโs topology, more specifically the Skyrmion topology, describes the correlation between lightโs position and polarization. Skyrmions have been shown to be invariant to isotropic noise; whether topology is invariant to random media is...
Early detection and treatment of TB remain key strategies to reduce transmission and disease progression. However, this is hampered by time-consuming, insensitive diagnostic methods, particularly for the detection of drug-resistant forms and in patients with human immunodeficiency virus infection (HIV). Several genes, such as RNA polymerase ฮฒ subunit (rpoB) and enoyl reductase (InhA) genes,...
Abstract: Accurate and timely diagnostics are essential for identifying infected individuals, enabling prompt treatment and control strategies to prevent further spread. The COVID-19 pandemic highlighted the critical role of diagnostic testing for disease preparedness and response. Conventional diagnostic techniques such as polymerase chain reaction (PCR) are effective at detecting viral...
Abstract
The precise monitoring of chemical concentrations in liquids is critical for environmental, industrial, and biomedical applications. Optical fiber sensors, particularly those based on Fabry-Perot interferometry (FPI), offer high sensitivity, tolerance to harsh environments, and multi-sensing capabilities, making them ideal for detecting refractive index changes in various...
Group delay dispersion (GDD) plays an important role in the creation and control of ultrashort pulses. As ultrashort pulses travel through dispersive media, the different frequency components travel at different speeds, increasing the pulse duration due to broadening of the pulse temporal profile. To create transform limited pulses (pulses that are as short as allowed by the available...
This research demonstrates voltage-based control of a Distributed Feedback (DFB) laser, forming a foundational step toward the implementation of an Optical Phase-Locked Loop (OPLL). The voltage control mechanism is realized through a Frequency-to-Voltage Converter (FVC) using the LM331, which converts an offset frequency - generated by frequency mixing of a signal generator and a stable...
We present Pulsed Laser Ablation in Liquid Solution (PLAL), a one-step pulsed laser ablation technique that produces a stable Ag-H2O nanofluid with improved thermal conductivity. Throughout the synthesis procedure, several deposition durations and fluences of the Nd YAG. Spherical nanoparticles (21โ37 nm) having instability at higher concentrations are revealed by characterization. At 45ยฐC (ta...
ZnSe:x% Ce3+ (x = 0, 2, 4, 6, 8 and 10) thin films were deposited using chemical bath technique. All the films samples revealed wurtzite phase ascribed to ZnSe and the presence of the Ce3+ did not change the films structure apart from the shift in peak position to longer wavelength when compared to the undoped sample. The red shift is due to the incorporation of the...
Quantitative Phase Imaging (QPI) is an imaging technique enabling non-invasive, label-free measurement of optical path length differences within samples, facilitating three-dimensional reconstruction from two-dimensional microscopy data. This is traditionally achieved using interferometric approaches such as Phase Shifting Interferometry (PSI) where interferograms generated by combining...
In Vitro Effects of Blue Laser Light as an Antimicrobial Agent on Microbial-Infected Fibroblast Cells
<u>Francis Obeng Brenya1 and Nicolette Nadene Houreld1
1Laser Research Centre, Faculty of Health Science, University of Johannesburg, Johannesburg, South Africa
Pseudomonas aeruginosa, Staphylococcus...
Tendons are frequently damaged by acute injuries, such as sports injuries or chronic overuse and age-related degeneration. Native tendon healing is lengthy and ineffective due to the tissue's inherently low cellularity, limited vascularization, and low metabolic activity of resident tenocytes. Natural healing is often accompanied by fibrosis, adhesion formation and re-injury is common. Current...
Delayed wound healing is among the major peripheral complications of diabetes. Synergistic treatment of diabetic wounds with phytochemicals and non-invasive techniques such as photobiomodulation (PBM) has shown promising results. Cells rely on glucose metabolism for the generation of adenosine triphosphate (ATP) for energy utilization. However, glucose metabolism is altered in diabetic wounds...
Single-molecule spectroscopy (SMS) has significantly advanced our understanding of the properties and dynamics of biomolecules. However, the environment used in SMS experiments is a poor representation of the natural cellular environment, and therefore the results of these studies may be of limited physiological relevance. One limitation of conventional SMS experiments is the need to...
Plants live with a continuous paradox: while light is the lifeblood for their growth, too much light can be extremely harmful. Their photosynthetic machinery, therefore, regulates the amount of absorbed energy in a photoprotective process known as non-photochemical quenching (NPQ). Aggregation of the main light-harvesting complex of plants, LHCII, is considered an excellent model system for...
The automatic photoprotective mechanisms of photosynthetic antenna complexes that initiate light-harvesting have been a subject of great interest for potentially improved solar energy technology, enhanced crop efficiencies, and biosensing. Light-Harvesting Complex II (LHCII) is the main pigment-protein antenna in green plants and exhibits the remarkable capability to switch between a...
Silver nanoparticles (AgNPs) have attracted considerable interest in cancer therapy, whereby their cytotoxicity is largely associated with the production of reactive oxygen species (ROS), as well as interfering with cancer cell energy metabolism and multidrug resistance. Other than their inherent cytotoxic potential, AgNPs have advanced significantly as carriers for drug delivery, improving...
Breast cancer continues to be one of the main causes of cancer-related deaths among women globally, highlighting the need for new, targeted, and less harmful treatment options. Gold nanoparticles (AuNPs) have been identified as potential tools in nanomedicine due to their compatibility with biological systems, customizable surface chemistry, and distinctive optical characteristics....
Pheophorbide a (PPBa) is a natural compound derived from chlorophyll, and its photophysical and photochemical properties makes it useful as a photosensitizer for photodynamic therapy (PDT). However, PPBa stability in biological environments and its bioavailability are crucial for effective therapy. Nanoparticle formulation of PPBa can improve its solubility and stability. The aim of this study...
Fluorescence (spontaneous emission) is a highly sensitive probe for a multitude of molecular processes during the light-dependent steps of photosynthesis in numerous organisms. In living organisms, the fluorescence signal is dwarfed by reflection and scattering; however, the signal-to-noise ratio can be significantly enhanced by gating the fluorescence to sub-ms excitation pulses through a...
Quantum ghost imaging (QGI) makes use of a pair of quantum entangled photons whereby one interacts with an object while spatial projective measurements are performed on the other. Using the correlated detections of the entangled photons, the transverse spatial profile of the object can be retrieved. QGI has recently been used to retrieve phase information of a field, however the depth profile...
Melanoma, a highly aggressive and metastatic form of skin cancer, frequently exhibits resistance to conventional treatments such as chemotherapy, radiation therapy, and surgical excision, highlighting the necessity for novel therapeutic approaches. Recently, integrating nanotechnology with photothermal therapy (PTT) has emerged as a promising strategy, offering targeted, minimally invasive...
Cancer is a deadly disease that continues to claim the lives of its victims on a global scale. Lung cancer, a prevalent and deadly malignancy, arises from the uncontrolled growth of cells within the lungs. Comprising of non-small cell lung cancer (NSCLC) and small cell lung cancer (SCLC), this disease poses significant challenges in diagnosis and treatment. Therefore, there is a dire need to...
G Kah, and H Abrahamse
Laser Research Centre, Faculty of Health Sciences, University of Johannesburg, P.O. Box 17011, Doornfontein 2028, South Africa.
Email: habrahamse@uj.ac.za
Abstract. Melanoma is a very aggressive and lethal type of skin cancer due to its elevated propensity to spread to other organs. Melanoma treatment has advanced significantly in the past decades, with...
Photodynamic therapy (PDT) is an emerging treatment modality that utilizes photosensitizers and light to induce cytotoxic effects in cancer cells. This study investigates the combined therapeutic potential of hypocrellin B (HB) and quercetin (Quer) in PDT against human breast cancer cell lines. The primary objective was to evaluate the effects of PDT with HB, Quer, and their combination on...
Skin cancer may be classified into three types - cutaneous malignant melanoma, squamous cell carcinoma, and basal cell carcinoma. Radiotherapy, chemotherapy, targeted therapy, and immunotherapy are some of the traditional therapies, all of which present significant side effects. Photodynamic treatment has revolutionized cancer treatment because of its effectiveness against various cancer types...
Melanoma is the deadliest form of skin cancer, with a rapidly increasing incidence and a poor prognosis for patients diagnosed at advanced stages. Despite several available treatments, including surgical excision, chemotherapy, radiation therapy, and immunotherapy, resistance to these therapies remains a significant challenge, particularly when the tumour has metastasised. Photodynamic therapy...
Background: Oesophageal cancer is a malignant disease that accounts for the seventh major cause of cancer-associated death worldwide. Hypocrellin B, a natural photosensitizer, has been employed for photodynamic therapy for various neoplastic diseases. However, studies that utilize hypocrellin B-based- photodynamic therapy on oesophageal cancer are limited. This current study examined the in...
