Real-time gas sensing using terahertz quantum-cascade lasers

This project will develop fast detection systems to provide the first real-time gas sensing in the terahertz (THz) band of the electromagnetic spectrum.<br /> <br /> The THz band lies between the infrared and microwave regions and represents a meeting between electronic and optical technologies. Although numerous potential applications for THz sensing exist, including atmospheric and space research, security and biomedical imaging, and industrial inspection, there has been limited practical use of THz systems outside specialised laboratories.<br /> One key reason for this is the reliance on relatively slow thermal detectors to measure and analyse THz signals. These are inadequate for studying rapidly changing systems, such as chemical reactions. They are also highly susceptible to background thermal noise, which limits the accuracy and dynamic range of measurements. In this project, the student will develop new high-speed THz gas-sensing techniques, taking advantage of recent developments in fast THz detector technology.<br /> <br /> They will initially demonstrate THz spectroscopy using a multi-pass optical cavity, enabling THz waves to pass many times through gases, improving sensitivity by a factor of ~100. They will integrate a fast, and sensitive TeraFET detector into this system, in collaboration with Goethe University Frankfurt, to detect and analyse rapidly changing chemical concentrations for the first time. They will then integrate an ultraviolet laser or flashlamp into the system to "trigger" photochemical reactions, and analyse the reaction processes on sub-microsecond timescales.

<p style="margin-bottom:11px">The studentship enables a step-change in the speed and accuracy of THz sensing and imaging techniques, which have historically been limited by the availability of good THz detectors. Ultimately, this will allow direct THz analysis of chemical reactions for the first time.  This would provide key missing links in atmospheric chemistry (e.g., impact of volatile-organic compounds on the lifetimes of greenhouse gases), which currently introduce order-of-magnitude uncertainties in climate models.  There are far wider potential impacts though, in terms of high-speed industrial emission monitoring and control, video-rate biomedical sensing, and the first potential satellite deployment of fast and low-noise THz receiver systems.</p> <p>Key objectives include:</p> <ul> <li><strong>Real-time analysis of chemical reactions using THz radiation:</strong> The PGR will use a broadband TeraFET detector to undertake analysis of gas reactions (e.g., deuteration of methanol) and flux rates (e.g., ammonia concentrations), leading ultimately to development of the first UV-pump/THz-probe reaction studies of atomic oxygen concentrations as an analytical chemistry technique.</li> <li><strong>Multi-pass THz gas analysis:</strong> The PGR will employ a bespoke multi-pass gas cell, allowing two orders of magnitude improvement in the sensitivity of gas measurements.  This will, for the first time, allow THz analysis of trace reactive gases, at the concentrations found within the Earth’s upper atmosphere, allowing reaction products to be studied to high precision.</li> <li><strong>UV pump-THz probe photolysis studies: </strong>The student will use ultraviolet-pumped photolysis techniques to study the reaction pathways of important atmospheric gas-phase species.  This will allow the fate of volatile organic compounds in the Earth’s upper atmosphere, and their impact on climate to be determined.</li> </ul> <p>The project will include working closely with our UK and international project partners, with the opportunity to travel to partner sites and international conferences.</p> <p>Applicants should have a first degree at the level stated in the <strong>Entry Requirements</strong>, in Engineering, Chemistry, Physics, or a related discipline, and must be able to demonstrate successful experience in independent technical or scientific project work. </p>

<p>Formal applications for research degree study should be made online through the <a href="https://www.leeds.ac.uk/research-applying/doc/applying-research-degrees">University's website</a>. Please state clearly in the Planned Course of Study section that you are applying to <em><strong>PhD Electronic & Electrical Engineering FT</strong></em> and in the research information section that the research degree you wish to be considered for is <em><strong>Real-time gas sensing using terahertz quantum-cascade lasers</strong></em> as well as <a href="https://eps.leeds.ac.uk/electronic-engineering/staff/375/alexander-valavanis">Dr Alexander Valavanis</a> as your proposed supervisor. Please state in the Finance section that the funding source you are applying for is <em><strong>School of Electronic & Electrical Engineering Studentship 2025/26.</strong></em></p> <p>If English is not your first language, you must provide evidence that you meet the University's minimum English language requirements (below).</p> <p><em>As an international research-intensive university, we welcome students from all walks of life and from across the world. We foster an inclusive environment where all can flourish and prosper, and we are proud of our strong commitment to student education. Across all Faculties we are dedicated to diversifying our community and we welcome the unique contributions that individuals can bring, and particularly encourage applications from, but not limited to Black, Asian, people who belong to a minority ethnic community, people who identify as LGBT+ and people with disabilities. Applicants will always be selected based on merit and ability.</em></p> <p class="MsoNoSpacing">Applications will be considered after the deadline.  Potential applicants are strongly encouraged to contact the supervisors for an informal discussion before making a formal application.  We also advise that you apply at the earliest opportunity as the application and selection process may close early, should we receive a sufficient number of applications or that a suitable candidate is appointed.</p> <p><strong>Please note that you must provide the following documents in support of your application by the closing date of 31 January 2025:</strong></p> <ul> <li>Full Transcripts of all degree study or if in final year of study, full transcripts to date</li> <li>Personal Statement outlining your interest in the project</li> <li>CV</li> </ul>

Applicants to research degree programmes should normally have at least a first class or an upper second class British Bachelors Honours degree (or equivalent) in Engineering, Chemistry, Physics, or a related discipline. Applicants who are uncertain about the requirements for a particular research degree are advised to contact the School or Graduate School prior to making an application.

The minimum English language entry requirement for research postgraduate research study is an IELTS of 6.0 overall with at least 5.5 in each component (reading, writing, listening and speaking) or equivalent. The test must be dated within two years of the start date of the course in order to be valid. Some schools and faculties have a higher requirement.

<p class="MsoNoSpacing">A highly competitive School of Electronic & Electrical Engineering Studentship consisting of the award of fees, together with a tax-free maintenance grant of £19,237 per year for 3.5 years.  Training and support is also provided.</p> <p>This opportunity is open to all applicants.  All candidates will be placed into the School Electronic & Electrical Engineering Studentship Competition and selection is based on academic merit.</p> <p style="margin-bottom:11px">You will be responsible for paying the overtime fee in full in your writing up/overtime year (£320 in Session 2024/25), but the scholarship maintenance allowance will continue to be paid for up to 6 months in the final year of award.</p> <p><strong>Important:</strong> Please note that that the award does <em><strong>not</strong></em> cover the costs associated with moving to the UK.  All such costs (<a href="https://www.leeds.ac.uk/international-visas-immigration/doc/applying-student-visa">visa, Immigration Health Surcharge</a>, flights etc) would have to be met by yourself, or you will need to find an alternative funding source. </p> <p style="margin-bottom:11px">Please refer to the <a href="https://www.ukcisa.org.uk/">UKCISA</a> website for information regarding Fee Status for Non-UK Nationals.</p>

<p>For further information about your application, please contact PGR Admissions by email to <a href="mailto:EMAIL@leeds.ac.uk">phd@engineering.leeds.ac.uk</a></p> <p>For further information about this project, please contact Dr Alexander Valavanis by email to <a href="mailto:a.valavanis@leeds.ac.uk">a.valavanis@leeds.ac.uk</a> or by telephone to + 44 (0) 113 343 3224.</p>