School of Physics (ETDs)
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Item Broadband beam shaping(University of the Witwatersrand, Johannesburg, 2024-03) Perumal, Leerin Michaela; Forbes, Andrew; Dudley, AngelaLaser beam shaping is a venerable topic that enjoyed an explosion in activity in the late 1990s with the advent of diffractive optics for arbitrary control of coherent fields. Today, the topic is experiencing a resurgence, fueled in part by the emerging power of tailoring light in all its degrees of freedom, so-called structured light, and in part by the versatility of modern day fabrication and implementation tools. Since its development, structured light has become a priceless tool in various applications such as telecommunication, imaging and microscopy, industrial manufacturing, quantum computing, optical trapping and medical treatments, to name a few. With recent advancements in these various applications, broadband beam shaping (creating structured light with many wavelengths) has become topical as it offers an additional degree of freedom for one to manipulate. In this thesis we look at how to generate broadband light using both digital and physical beam shaping optics. In so doing we provide a method to introduce broadband beam shaping into various applications that may benefit from either the compact size of a physical optic or the dynamic ability of a digital.Item Digital toolbox for the generation and detection of vectorial structured light(University of the Witwatersrand, Johannesburg, 2023-06) Singh, Keshaan; Dudley, Angela; Forbes, AndrewLight has been an invaluable tool in the development of the modern world, with the myriad of applications increasing along with our degree of control over it. From the development of coherent light sources, to the shaping of amplitude and phase, this development has not ceased for the past half century. The field of structured light, borne out of the necessity and desire for control over light, has been growing steadily in recent years. In the spatial domain, the control over light’s polarization (i.e., the local planes in which the electric and magnetic fields oscillate) has been the most recent avenue of improvement, providing enhancements to a variety of applications ranging form microscopy and communication to materials processing and metrology. This class of light, commonly referred to as vectorial light, often requires specialised equipment in order for its its creation before its numerous benefits can be exploited. These tools often incur high costs and suffer from limitations relating to the diversity of vectorial light they can create, wavelength dependence and slow refresh rates. This thesis follows the development of a series of digital tools for the versatile generation and analysis of vectorial light using low-cost core technologies which can operate at high rates over a broad wavelength range. We follow the development of the generation tool in the context of its application in generating novel accelerating polarization structures, emulating vectorially apertured optics, generating probes to measure birefringence and chirality and creating synthetic spin dynamics. The development of the analysis tool is explored by investigating its application in performing automated digital Stokes polarimetry measurements, completely characterizing the internal degrees of freedom of arbitrary vectorial light and acting as a polarization and wavelength independent wavefront sensor. We then demonstrate how these tools can be used, in conjunction, to investigate the fundamental invariance of vectorial light to perturbing channels and how this invariance can be exploited in a highly robust novel communication scheme. In addition to demonstrating the applicability and versatility of these vectorial light tools, the applications offered a means to highlight areas for the optimization for the design. This culminated in the ongoing prototyping of versatile, fast, broadband devices which operate stably and have a small physical footprint.