The project here aims to challenge the status quo of metrology and propose the progression towards future metrology and automated manufacturing, stepping towards Industry 4.0. Industry 4.0 represents a paradigm shift towards digitally integrated, data-driven, and autonomous manufacturing systems. Its global economic impact is substantial, with estimates from McKinsey & Company suggesting that Industry 4.0 technologies could generate up to $3.7 trillion in value annually by 2025, while PwC reports that digitalisation could contribute over $15 trillion to global GDP by 2030. Strategic initiatives such as Industrie 4.0 and the UK’s Made Smarter highlight the national-scale prioritisation of smart manufacturing, aiming to boost productivity by up to 25% and reduce operational costs by up to 30%. This shift in manufacturing necessitates the integration of real-time, in-situ metrology and compact sensing technologies, rendering advanced optical and nanophotonic systems as critical enablers for next-generation manufacturing environments. The project therefore, provides the vision towards shifting the paradigm in measurement technologies, disrupting the industry and boosting metrology capabilities. This is done by first identifying the downfalls of current metrology systems and instrumentation applied in manufacturing. This includes the current cost of making traditional glass optics, the bulkiness, weight and overall size of the final instruments, making it cumbersome to make measurements as parts have to be taken off the manufacturing line, inducing human errors, spatial repeatability problems as well as it is a time-consuming manual process. Driven by the need for compact metrological instruments, this thesis explores the use of optical metasurfaces to miniaturise chromatic confocal probes. Ultra-thin metasurfaces offer significant size reduction compared to traditional glass lens-based systems, especially when coupled with optical fibre. The research focuses on designing metasurfaces to replace the bulky optics found in commercial chromatic confocal probes, thereby investigating novel designs that manipulate chromatic dispersion for diverse applications in manufacturing and metrology. This then leads us to the ultra-compact concept, which refers to the ability of significantly thinning the axial thickness of an equivalent traditional glass optics, resulting in a device that can be integrated onto a surface with minimal profile. On the other hand, this also enables the encapsulation of multiple functionalities of various conventional optical elements into a single low profile element, which in turn shrink down the overall size of the instrument that is significantly smaller than what can be achieved with the commercially available optical instruments. This project has achieved certain goals, such as the realisation of multiple metasurface-based chromatic confocal probes, expanding the ability of fibre probe sensing, while also introducing a plethora of metasurface designs where each is suitable for a different measurement range, providing solutions for different potential applications and use cases. It started off with a systematic approach, whereby the most basic metalens was designed for a collimated source for ease of alignment and circular pillars to avoid polarisation dependency, which provided a focal range of 230 μm over wave-length range of 140 nm from 560 nm to 700 nm. Later, metalens designed for point source was also introduced to better adapt to the on-fibre integration that advances towards an ultra-compact chromatic confocal probe, which yielded a focal range of 294 μm over the same wavelength range. Another variation of the metalens was designed using square nanopillars, adopting the larger phase variation across the pillars as a means for stronger chromatic dispersion, giving a focal range of 300 μm over the same wavelength range. These achievements contribute towards the larger goal of metasurface-enabled chromatic confocal probe for on-machine and in-situ measurement, while also providing various options suitable to different applications and situations. The metalens based device would be suitable for the metrology of relatively low roughness and smooth surfaces, so as to minimise influence of scattering on the returned signal, which directly influence the signal-to-noise ratio (SNR) and prone to broadening or distorting of the spectral peaks. Measuring of silicon wafers, thin films and optical coatings would be a potential application tailored to its strength, while also being reflective enough to yield strong peak signals. Polished metal surfaces would also be a suitable candidate due to its reflectivity, while metal additive manufacturing parts benefit from the compactness of metalens-based probes and the ability to reach into tiny orifice, the higher surface roughness may not be the most fitting candidate for the probes. Recognising the demands of the industrial environment, designs with a cover layer and monolithic designs were designed and manufactured to enhance the robustness and durability of the probes, bringing practicality into context and therefore stepping closer towards industrial implementation and deployment. Further experiments are yet to be completed to validate the practicality of these designs.
| Date of Award | 7 May 2026 |
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| Original language | English |
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| Supervisor | Haydn Martin (Main Supervisor) & Jane Jiang (Co-Supervisor) |
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