Silicon photonics is a powerful technological platform that has advanced with gigantic steps during the past 20 years. Its applications range from the nanoscale, with biosensing and spectroscopy, all the way to the macroscale, with optical fiber communications and on-chip Lidar. However, its commercialization is still hindered by the lack of a cost-effective and automatable chip packaging approaches. At the same time, the current multiplexing techniques to increase the bandwidth density of optical communication networks are hitting their theoretical capacity limits. This has pushed the community to look for additional spatial data transmission paths through a common optical fiber. At the smaller end of the size scale, the controlled self-assembly of nanoparticles is the holy grail of nanotechnologists around the globe. Great advances towards this goal have been demonstrated, but most of the time it is hard to simultaneously control the many variables involved in the self-assembly processes. Silicon photonics and compatible wave guiding techniques are the ideal platform to address these issues thanks to their ability of controlling light in the nanoscale. Regarding the macroscale, this dissertation presents approaches based on micro 3D printing to overcome the silicon photonics packaging bottleneck and to access additional spatial channels to increase the bandwidth density of optical communication channels. Section 2.2 presents the plug-and-play coupling of fibers to waveguides, where a 3D printed optical-mechanical micro connector is defined directly on top of a silicon photonics chip. This connector has such a relaxed alignment tolerance, that even the coarse precision of industrial automated assembly tools is enough to automatically couple a fiber to the waveguide in a robust and passive way. Section 2.3 shows another 3D printed micro coupler design. This coupler optically bridges between the higher order modes of a multimode silicon waveguide and those of a few-mode fiber. These higher order modes can carry different streams of information at the same wavelength, effectively increasing the amount of data transmitted through the same physical channel. Regarding the nanoscale world, there is a very popular but not completely well understood self-assembly technique called evaporative self-assembly. For the past couple of decades scientists have been trying to harness it to deposit controlled patterns of nanostructures (ranging from inorganic nanoparticles to biological elements). The problem with this technique is that several of the physical variables involved in the evaporative self-assembly process are coupled to each other, making it difficult to precisely control the particle deposition. Section 3.3 shows a way of depositing a periodic pattern of gold nanoparticle clusters along the top of a silicon photonics waveguide by assisting the evaporative self-assembly process with optofluidic transport of particles. The particle trapping and transport along a waveguide is possible thanks to the strong optical forces in the immediate vicinity of the waveguide core. With this approach, the evaporative self-assembly deposition pattern periodicity can be controlled simply by tuning only one knob: the input laser power.

The THz region is a burgeoning field of research with applications in spectroscopy, integrated circuit fabrication, bio-medicine, and communications. Until recently, the THz region was largely unexplored, mainly due to the technical difficulties involved in making efficient and compact sources and detectors. As these challenges are addressed, the focus of research has shifted to practical applications, such as sensing and imaging. The focus of this thesis is to investigate the characterization of parallel plate waveguide multimode propagation and periodically notched resonant structures for use in sensing and material parameter extraction applications. Broadband and narrowband measurements are presented and analyzed. Measurements are compared to finite difference time domain simulations and analytic solutions that use a Fourier transform mode-matching technique. Agreement is observed between simulation and measurement of radiation patterns. Weighted estimates of individual mode analytic solutions produce equivalent radiation patterns, which allows insight into the energy coupled into each respective mode. Results show that higher order modes contribute both a greater conductive attenuation and higher coupling loss. Agreement is also observed between measurements and simulated single and periodically notched resonant structures. Results demonstrate shifting of the resonant peak with respect to changes in plate separation for the periodically notched structure. For the single notch resonator, simulations indicate the resonant peak is dependent on notch depth until the depth-to-width ratio is greater than two. This work demonstrates that multimode propagation can be identified and the amount of energy coupled into each mode may be estimated using radiation patterns. Experiments using quasi-optical time domain spectroscopic and continuous wave vector network analyzer systems in the THz region have been demonstrated. Finite difference time domain simulations have validated measurements on both systems. The results presented will advance the field of THz research by aiding in the design and analysis of sensing and material parameter extraction systems

A RESEARCH REPORT submitted in partial fulfilment of the requirements for the degree of MASTER OF SCIENCE in the SCHOOL OF SCIENCE EDUCATION of the UNIVERSITY OF THE WITWATERSRAND / This study was designed to investigate beliefs of Physics Teachers, in Lesotho, about Physics and Physics teaching and their awareness of students' alternative conceptions. The study used three questionnaires as its research tools. The first questionnaire investigated beliefs of teachers about Physics concepts, particularly electromagnetism, and the teaching of those concepts. An 'index of agreement' was calculated to determine the tendency of responses. The second queatlonnalre investigated teachers' awareness of students' alternative conceptions, while the third investigated Students' alternative conceptlons. Teachers' predictions are compared with the students' answers. The study shows some teachers having beliefs which can be grouped into two categories, namely constructlvlsts and empiricists. There is however no clear separation between the two categories. The study also shows that some teachers are not aware of students' alternative conceptlons, while some teachers had the same alternative conceptions as students, / Andrew Chakane 2019

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A remote sensing system for measuring ocean surface currents is presented in this thesis. Included are a review of the Stepped Frequency Delta K (SFDK) radar system hardware, a description of the system performance, experimental results of ocean current measurements, and comparisons of the measurements with a conventional current probe and a wind driven current model. Important features of this radar system are (1) its capability to perform real time processing of the collected data and (2) its frequency agility, which provides significant improvement of the system's signal-to-clutter ratio. The real time processing capabilities were essential to the collection and monitoring of the ocean currents for long periods of time that is necessary to understand and interpret the results. The SFDK radar participated in two month long experiments. During the first experiment at N. Truro, MA, the SFDK radar demonstrated its ability to make precise phase velocity measurements over long periods of time. During the second experiment on the Chesapeake Light Tower, the radar was able to sense both tidal and wind driven current components. Comparison of radar data and in situ measurements during the CLT experiment shows that the instrument possesses a unique capability to measure near surface currents--not possible with in situ probes.

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