Conveners
Photonics: Biophysics
- Pieter Neethling (Laser Research Institute, University of Stellenbosch)
Photonics: Spectroscopy and Imaging
- Gurthwin Bosman (Stellenbosch University)
Photonics: Lasers and Quantum Communication
- Angela Dudley ()
Photonics: Beam Shaping and Quantum Applications
- Andrew Forbes (U. Witwatersrand)
Photonics
- There are no conveners in this block
Photonics
- There are no conveners in this block
Photonics
- There are no conveners in this block
Despite advances in cancer treatment, lung cancer remains one of the leading causes of cancer deaths worldwide. Lung cancer can spread through the blood and lymphatic systems, as well as infiltrate healthy tissues underlying the lung, resulting in both distant and local metastasis. The most common causes of death are cancer metastasis and the threat of secondary tumours. The ability of cells...
Mitogen Activated Protein Kinase (MAPK) signalling is one of the best characterised signal transduction pathways in cell biology and is involved in wound healing processes. Photobiomodulation (PBM) has been used to induce physiological changes and has been shown to improve wound healing processes, however underlying molecular and cellular mechanisms of action remain largely unexplained. The...
The central nervous system (CNS) of mammals is limited in its repair and regeneration in the event of injury due to trauma or neurodegeneration, therefore, optimization of its regeneration capabilities is necessary. Studies have shown that this issue may be addressed through the transdifferentiation of adipose-derived mesenchymal stem cells (ADMSCs) into neuronal cells. This process has not...
Metastatic Melanoma (MM) is highly aggressive and is among cancers causing major global deaths annually. It is imperative to find therapies that can eliminate MM and has become a major concern due to the potential for cancer relapse and metastasis, as well as the disease being accounted to be resistant to multiple forms of therapy. This in vitro study explores the effect of Photodynamic...
Abstract. Colorectal cancer (CRC) is a fatal malignancy with limited therapeutic options and its incidence is on the rise in recent years. Photodynamic therapy (PDT) has emerged as a promising minimally invasive therapeutic modality that employs three fundamentals to induce tumour damage: a photosensitizer (PS), light of a specific wavelength and molecular oxygen. However, PDT has shown...
Cancer is a global emergency that needs instant intervention. Breast cancer is the second most common cancer after Lung, and the first most common cancer amongst women. Current treatments are linked with adverse side effects, treatment failure and cancer relapse. Photodynamic therapy (PDT) is one of the emerging cancer treatment options that is highly selective and specific towards cancer...
Electric Field Induced Second Harmonic (EFISH) generation is a technique to probe the structure of and charge transfer across buried interfaces. It is particularly suitable to study the Si/SiO2 interfaces that are crucial in electronics undergoing continuous miniaturization. This makes it important to investigate the interaction of the front and rear Si/SiO2 interfaces of thin silicon...
Light sheet fluorescence microscopy is a powerful tool within the field of microscopy. The inherent advantages over other fluorescence microscopy techniques inclue high sectioning capabilities, reduced photo-damage in the sample and short data acquisition times.
In this presentation, the development of a light sheet microscope is described. The system relies on the use of a thin sheet...
Optical tweezers have found countless applications in the fields of physics and biology ever since its advent in 1986 by Arthur Ashkin. Using only focused light, optical tweezers are able to trap and manipulate microscopic particles. In this work, we investigate the possibility of combining the optical tweezer with fluorescence spectroscopy to develop an ultra-sensitive analytical instrument....
We investigate Mie scattering from particles in an optical trap. Optical tweezers and counter propagating optical traps allow micron sized particles to be optically trapped and investigated by scattering white light off the particles. In optical tweezers, a high numerical aperture microscope objective is used to focus a laser beam and create an optical trap for microscopic particles, such as...
Any image of a point source in a diffraction-limited system will result in a blurred pattern, the point spread function (PSF). In the case of fluorescence microscopy, incoherent imaging modality can be described by a convolution of the object with the PSF, a common approach to improve the image quality tries to undo this convolution. A successful deconvolution requires a good model of the PSF...
Resonance Ionization Spectroscopy (RIS) is a spectroscopic technique that relies on the resonant excitation of an atom using lasers. The process involves series of atomic excitations, with at least one resonant transition, and ends when the atom is ionized. The RIS process can be applied in the production and study of rare and exotic nuclei via radioactive ion beams at accelerator facilities...
Photonics and Lasers have become the centre of several modern day technologies such as the internet, additive manufacturing, remote sensors and even entertainment. They have revolutionized how we view Physics opening the door to a plethora of applications and new Photonics phenomena. In this non-specialist lecture we will take you on a trip through the development of lasers and the concept of...
It is well understood that structured light becomes distorted after propagating through the atmosphere. These distortions are the result of random refractive index fluctuations, themselves a product of atmospheric turbulence. In particular, these distortions have been realised as modal crosstalk in beams carrying orbital angular momentum. Such beams are ubiquitously used in free space optical...
High dimensional entangled quantum systems are important in various applications such as quantum teleportation, secure quantum key distribution and cryptography. Such applications require a method to characterize the state density matrix. Conventional methods such a Quantum State Tomography work, however, can become computationally cumbersome if the dimension becomes too great. The method...
Structured light beams from the Laguerre-Hermite-Gaussian mode families with scalar or vector polarization structures have found applications in many diverse areas, particularly in high dimensional quantum communication, optical particle trapping and super-resolution microscopy. However, only a small subset of these structured beams, namely, the radially and azimuthally polarized annular...
Hermite-Gaussian laser modes are a complete set of solutions to the free-space paraxial wave equation in Cartesian coordinates. They are often referred to as transverse electromagnetic modes and represent a close approximation to physically realizable laser cavity modes. Their applications ranges from enhancing optical communications information capacity to description of optical fields as...
In this work, Stokes polarimetery is used to extract the polarization structure of optical fields from only four measurements as opposed to the usual six measurements. Here, instead of using static polarization optics, we develop an all-digital technique by implementing a Polarization Grating (PG) which projects a mode into left- and right-circular states which are subsequently directed to a...
Optical fields can often show unexpected effects when interference effects are used. Examples of these are angularly accelerating beams. In this work we present a novel structure of light that exhibits State-of-Polarization (SoP) structures that rotate with acceleration and deceleration when propagating in free space. We achieve this by creating a superposition of beams with accelerated...
Vector beams have inhomogeneous polarisation distributions that introduce a new degree of freedom that can be used to structure light. Pure vector beams have spatial and polarisation components that are non-separable affording them various interesting properties. Common examples include cylindrical vector vortex modes, Poincaré beams and vector beams on the Higher Order Poincaré Sphere. These...
The study of the spatial properties of light has been rapidly evolving in the past decades. One of many applications of studying spatial light can be found in the field of quantum optics and quantum information. In these fields of study, it has become increasingly important to shape beams in experiments. This is done in order to achieve a desired output, such as increasing the entanglement...
Light affords a convenient avenue for transmitting, encoding, computing and filtering information where structuring the spatial degree of freedom allows us to perform operations at the speed of light and transfer a large range of information simultaneously in both the classical and quantum realms of physics. For example, exploiting the spatial structure of light provides a notable increase in...
Quantum information processing beyond the traditional 2-dimensional qubit states has recently become topical, benefiting numerous applications such as quantum computing, quantum ghost imaging, quantum cryptography and quantum teleportation with high information capacities. The need to accurately characterize key performance parameters, such as the dimensionality of the encoding basis or the...
Different studies have proposed the efficacy of photobiomodulation (PBM) at different wavelengths (830 and 660 nm) to stimulate wound repair in diabetic cells. The TGF-β1/Smad cascade has proven to be an effective signalling pathway in differentiating fibroblasts into myofibroblasts. This study aims to compare the effects of both wavelengths on cellular viability and expression of fibroblast...
Single-beam coherent anti-Stokes Raman scattering (SB-CARS) spectroscopy is a special implementation of CARS which utilises a single broadband light source, as opposed to the up to three lasers found in a traditional implementation. This CARS configuration, in combination with spectral focusing, has been shown to be able to target and isolate chosen Raman transitions from broad spectra in...
Master Oscillator Power Amplifier (MOPA) systems have garnered considerable interest to power scale low power seed beams (from the Master Oscillator) to higher powers. These systems are favourable to obtain the desired laser beam performance when additional optical elements such as Bragg gratings are required. These elements do not have to endure high optical intensities inside high-power...
Breast cancer is a form of cancer that affects women and is regarded as the second leading cause of cancer-related deaths. Phyto photodynamic therapy is a promising therapeutic approach adopted in cancer research, which uses plant-derived bioactive compounds in combination with photosensitizers to induce apoptosis in cancer cells. Dicoma anomala is an African medicinal plant, that is widely...
Non-diffracting optical fields have exhibited numerous interesting properties, including self healing and radial acceleration, in addition to their propagation invariant intensities. Naturally, these properties have proven desirable in applications such as optical trapping, communication and metrology. One class of these fields is the set of Bessel-Gaussian modes which can be generated through...
Entangled photon pairs are employed in quantum ghost imaging to facilitate an alternative image acquisition method. Individually, the information contained in each photon does not allow for image reconstruction, however, the image can be reconstructed by harnessing the power of the correlations that exist between the entangled photon pair. Interestingly, these photon pairs can be either...
Osteoporosis is a progressive, metabolic bone disease affecting millions across the globe. Stem cell regenerative therapy has demonstrated potential in treating osteoporosis, particularly when using Adipose Derived Mesenchymal Stem Cells (ADMSCs). Photobiomodulation (PBM) has gained international momentum due to its ability to aid in the proliferation and differentiation of stem cells....
Resonant Ionisation Spectroscopy (RIS) refers to the selective excitation of a particular atomic isotope to an excited state by means of resonant light, followed by photo-ionisation and ion detection. ⁶⁸Zn and ⁶⁷Zn are important stable nuclides in medicine and industry. ⁶⁸Zn and ⁶⁷Zn are used to produce Gallium isotopes (⁶⁸Ga and ⁶⁷Ga) that are used in medical imaging such as Positron...
Optical fields with an embedded phase singularity are referred to as vortex beams as they carry and impart Orbital Angular Momentum (OAM). They have been found to be attractive in various applications such as optical trapping, quantum communications, laser ablation, manipulation of atoms and micro particles and surface structuring. Techniques to select vortex beams vary from spiral phase...
One of the largest problems faced in free space optical communication is the influence of atmospheric turbulence on a beam’s structure. Thus, investigating the effects of turbulence on beams has become a major research area in recent years. Experiments within this research area have mainly been performed by generating turbulence within a laboratory setting using, for example, phase screens on...
Lehloa Mohapi1, Andrew Forbes1 and Angela Dudley1
- School of Physics, University of the Witwatersrand, Private Bag 3, Johannesburg 2050, South Africa
The generation of unique spatial profiles for high-power applications is becoming more topical, ranging from high-power, high bandwidth optical communication to spatial profile control in additive manufacturing and other laser-material...
Controlling the spatial profile of light through optical fibres is extremely useful in being able to deliver tailored high-power beams directly to the point of contact, as well as in optical communication systems. In this presentation, we compare various types of optical fibres, ranging from single mode, multi-mode step index and graded core fibres, as well as photonic crystal fibres. We first...
Abstract. Colorectal cancer (CRC), currently remains a challenge to diagnose and is the third most diagnosed cancer worldwide. Photodynamic diagnosis (PDD) is a promising early diagnostic approach which uses photosensitizers for fluorescence detection of malignant cancer cells without inducing tumour damage. In this study, ZnPcS4 a photosensitizer with pronounced chemical properties due to its...
This presentation discusses a noncollinear optical parametric amplifier as a source of ultrafast mid-infrared light for spectroscopic experiments and aims to provide a consistent method for the generation thereof. The proposed laser source at the Laser Research Institute is intended for the investigation of molecular vibrations of organic molecules on a femtosecond timescale. The underlining...
