Compact, ultra-sensitive gas sensing techniques

Detection and identification of gaseous species is crucial in applications spanning through defence and security, bio-medical, environmental monitoring and various others. Many techniques have been demonstrated over the years, with some demonstrating sensitivity to different molecules with concentrations as low as parts-per-quadrillion. However, such technologies are usually complicated with limited applicability beyond the lab. Therefore, there is still need for development of lightweight, compact and portable sensing devices that will bring the high sensitivity sensing into the field.
In this project we aim to place our focus on the photothermal family of the laser-based spectroscopic techniques and especially on the photoacoustic spectroscopy. Here the wavelength of an excitation source is chosen such that it is coincident with a molecular absorption of the compounds of interest. When these molecules are within the excitation range, a portion of that radiation is absorbed which in turn leads to weak heating - and thus a change in density. Modulation of the incident wave causes an associated modulation in density, resulting in a periodic pressure - or sound - wave. This sound wave can subsequently be detected with a microphone-type arrangement. It is an ideal laser-based gas trace detection technique as it allows to combine rugged, highly compact topology with potentially very high specificity (as conferred by the laser linewidth), selectivity (from laser tunability) and, potentially, sensitivity (matching that of laboratory-based techniques).
An exciting opportunity exists to develop and refine the spectroscopic work of the team at the Fraunhofer centre by combining their laser-based systems with the extensive expertise of Dr Michael Lengden gas sensing group, to generate novel sensing modalities.
The prospective student will be exposed to the laboratory-based experimental laser physics, as well as opto-mechanical, electronic and spectroscopic instrumentation design. In parallel, she/he will study all the aspects of the acoustic detection modules, such as spectrophones design and manufacture, their characterisation and calibration. As such this represents an ideal challenge for a candidate exhibiting strength in experimental physics, as in encompasses photonics and acoustics, electronics and associated instrumentation.
There is a strong desire to translate laboratory-based success into field-deployable demonstrators, and so a desire to engage with mechanical design and with potential end users is also highly desirable.

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.