Investigating the interaction between laser parameters for ultra-fast laser processing of glass

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This is a PhD research project in Physics. The project aim is to produce an empirical model for ultra-short laser material modification of glass (and specifically fused silica and borosilicate). To accomplish this the student will need to:-Characterise the effect of the laser on the glass through a combination of post process analysis (e.g. SEM, microscopy and phase microscopy) and in situ diagnostics. -Characterisation will include measuring key features (such as fictive temperature barriers, residual stress and physical dimensions of the glass modification.-In-situ diagnostic tests are expected to include phase holography, temperature and absorption measurements. -Significant reduction in the number of experiments to be performed will be achieved through the application of experimental design processes developed for manufacturing/engineering processes. The Taguchi method has been tentatively identified as a suitable approach however the student will be expected to carry out a literature review which will include a survey of potential methods as the starting point for the project. With a combination of experimental design, characterisation and diagnostics the student will assess the impact of a range of parameters on the laser-material process. This will include but will not be limited to: peak pulse power, pulse energy, pulse duration, repetition rate, scan speed, pulse overlap average power and focussed spot size. It is expected that the student will identify further parameters over the course of the project. ANOVA (or other statistical approaches as identified as appropriate) can then be applied to reduce these data to an empirical model (equation) equating the "manufacturing" (i.e. laser material interaction) result to the input parameters. Ideally this would produce an equation allowing an operator to "dial in" an appropriate set of parameters for a desired result without the need for significant process development tests. The equipment required for these experiments will include the existing ps/fs laser processing systems (Trumpf Tru Micro, Light Coversion Carbide) as well as a new laser system which is in the process of being procured for installation in mid-2019. Characterisation work will be carried out using existing imaging systems (SEMS, Microscopes etc.) as well as a polariscopic which has been constructed for use in a related project. Diagnostic work will rely on a series of new instruments: A pyrometer will provide temperature data, an integration sphere absorption data and finally a holographic imaging system (Cambridge TechWorks, Falcon Camera) will provide in site phase information. To a large extent the student will be responsible for commissioning/adapting these equipment for use in this application.