Development of Optical Sources for Gas Sensing Applications

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Laser-based absorption spectroscopy can be utilised in numerous industrial applications to measure species concentrations for process control, combustion diagnostics, environmental monitoring, and emissions measurement, and can be applied in various forms (wavelength modulation spectroscopy - WMS, cavity ringdown spectroscopy - CRDS, photo-acoustic spectroscopy - PAS). The Centre for Applied High Resolution Spectroscopy (CAHRS), within the Centre for Microsystems and Photonics in the EEE department has over 20 years of experience implementing these techniques with a large number of industrial and academic partners, including Rolls-Royce, Siemens, LG Fuel Cells, Optosci Ltd, M Squared Lasers. The aim of this studentship is to investigate various optical sources, and novel optical sensing techniques, for the measurement of the spectral parameters of target species (CO, CO2 and H2O). This will include the investigation of using fast tuning rate quantum cascade lasers, to understand the relaxation rates of excited molecules in high temperature environments, and broadly tunable source development around the 2000 nm region to investigate the pressure broadening effects of water vapour and carbon dioxide. In essence, the project will support the development of a disruptive chemical species measurement method for aero gas turbine engines (GTE) as well as the wider application to other combustion emissions. The student will begin by understanding the complexities of high accuracy measurements of spectroscopic parameters at high temperature and pressure. They will then model theoretical absorption spectra to ascertain which spectral features of the target gases are suitable for measurement in a combustor. The chosen spectra will then be measured experimentally to ensure suitability, and to measure the temperature dependence of their broadening parameters.