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

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 Innovation
The 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.

Complementing our Pathways to Impact document, here we state the expected real-world impact, which is of course the leading priority for our industrial partners. Their confidence that the proposed CDT will deliver valuable scientific, engineering and commercial impact is emphasized by their overwhelming financial support (£4.38M from industry in the form of cash contributions, and further in-kind support of £5.56M).

Here we summarize what will be the impacts expected from the proposed CDT.

(1) Impact on People
(a) Students
The CDT will have its major impact on the students themselves, by providing them with new understanding, skills and abilities (technical, business, professional), and by enhancing their employability.
(b) The UK public
The engagement planned in the CDT will educate and inform the general public about the high quality science and engineering being pursued by researchers in the CDT, and will also contribute to raising the profile of this mode of doctoral training -- particularly important since the public have limited awareness of the mechanisms through which research scientists are trained.

(2) Impact on Knowledge
New scientific knowledge and engineering know-how will be generated by the CDT. Theses, conference / journal papers and patents will be published to disseminate this knowledge.

(3) Impact on UK industry and economy
UK companies will gain a competitive advantage by using know-how and new techniques generated by CDT researchers.
Companies will also gain from improved recruitment and retention of high quality staff.
Longer term economic impacts will be felt as increased turnover and profitability for companies, and perhaps other impacts such as the generation / segmentation of new markets, and companies receiving inward investment for new products.

(4) Impact on Society
Photonic imaging, sensing and related devices and analytical techniques underpin many of products and services that UK industry markets either to consumers or to other businesses. Reskilling of the workforce with an emphasis on promoting technical leadership is central to EPSRC's Productive Nation prosperity outcome, and our CDT will achieve exactly this through its development of future industrially engaged scientists, engineers and innovators. The impact that these individuals will have on society will be manifested through their contribution to the creation of new products and services that improve the quality of life in sectors like transport, dependable energy networks, security and communications.

Greater internationalisation of the cohort of CDT researchers is expected from some of the CDT activities (e.g. international summer schools), with the potential impact of greater collaboration in the future between the next generations of UK and international researchers.