Stand-off, SPAD-enhanced Ultra-Violet Raman Spectroscopy

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The detection of substances at range is extremely important to a number of industrial production and safety processes. Raman is a potent optical technique by which the nature of a substance can be ascertained, but to date has been limited to contact / short-range stand of operation due to the weakness of the Raman scattering effect. In this programme, we will develop and evaluate different stand-off Raman spectrometers to solve different industrial, medical and safety issues in sectors such as the nuclear industry, mining, healthcare and pharma production. Technical Challenges & Our InnovationThe main limitations of available Raman spectrometers are:1) the weak Raman signals can be easily interfered by unwanted background fluorescence (for example the strong auto-fluorescence from biological samples), and 2) the acquisition is slow. Raman signals are instantaneously generated from samples after they are excited, whereas there is a certain delay before fluorescence signals are emitted. This delay is characterised by the fluorescence lifetime usually ranging from hundreds of picoseconds to tens of nanoseconds. To accurately measure Raman signals, the best detection strategy is to have a fast sensor capable of capturing only the Raman emission while ignoring the background fluorescence appearing in an ultra-short period of time later. Thanks to the recent advances in sensor technologies, we are able to apply innovative single-photon sensors (called SPADs) and picosecond stopwatches to pinpoint Raman signals robustly. The main objectives of this project are:(1) Developing multichannel picosecond stopwatches;(2) Integrating SPAD & picosecond stopwatch arrays; (3) Developing firmware/software for the developed system;(4) Conducting benchmark experiments & comparison studies with traditional Raman spectrometers; Engaing in impact generation activities;(5) Using UV excitation sources to maximise the intensity of the Raman scatter. We will integrate a single system refined for deployment in the envisaged end-user scenario; such an endeavour would represent a highly timely, novel and disruptive achievement. Our use of single-photon detectors also plays strongly into the UK Quantum Technologies agenda, and will result in a timely and highly innovative early industrial application of these devices.