Water-based THz optoelectronics

Supervisory Team: Prof Tim Freegarde and Dr Fabio Novelli

Explore and develop quantum-enabled, water-based emitters and receivers for terahertz (THz) radiation. The PhD candidate will explore the role of electronic coherence in light-driven aqueous solutions and develop prototype antennas for wireless communication at THz frequencies (6G). This project aims to provide greener, cost-effective liquid alternatives to conventional semiconducting materials.

This PhD project aims to explore the role of quantum electronic coherence in photo-excited water samples and develop new kinds of liquid-based devices for wireless terahertz (THz) communication. This approach exploits the transient coherent response of light-driven water, suggesting a shift from conventional electronic material, such as silicon or gallium arsenide, to cheaper, more abundant, and greener liquid alternatives.

Recent studies reveal that aqueous solutions can generate fast (20%) modulations at THz frequencies[1,2]. For example, when exposed to the bright optical radiation from ultra-fast amplified lasers, concentrated iodide solutions are strongly ionized, and the impulsively generated electrons are characterized by a mobility of ~1 cm^2/(V·s)[3] - comparable to that found in conductive polymers or amorphous silicon.

The role of quantum coherence in these processes, however, is unclear. Open questions include the role of nuclear quantum effects in the hydrogen-bonded network of liquid water molecules and the decoherence time of impulsively generated electronic wavefunctions. As the THz emission depends on the phase of the driving light fields, the quantum control of the delocalized electronic states may tune transient photocurrents and expand the available THz bandwidth.

The PhD candidate will contribute to every stage of the project and will have opportunities to broaden their expertise and network via interdisciplinary collaborations spanning optics, electronics, and chemistry. The position is ideal for candidates with a background in physics, physical chemistry, materials science, or (electrical) engineering. Experience with spectroscopy, optoelectronics, or photonics is advantageous.

[1] An ultra-fast liquid switch for terahertz radiation, APL Photonics 7, 121302 (2022)

[2] The birth and evolution of solvated electrons in the water, Proc. Natl. Acad. Sci. U.S.A. 120, e2216480120 (2023)

[3] High-mobility electrons in aqueous iodide solutions, ACS Omega (2025)

Entry Requirements

A very good undergraduate degree (at least a UK 2:1 honours degree, or its international equivalent).

Closing date: 31 August 2025. Applications will be considered in the order that they are received, the position will be considered filled when a suitable candidate has been identified.

Funding: We offer a range of funding opportunities for both UK and international students, including Bursaries and Scholarships. For more information please visit PhD Scholarships | Doctoral College | University of Southampton Funding will be awarded on a rolling basis, so apply early for the best opportunity to be considered.

How To Apply

Apply online:  Search for a Postgraduate Programme of Study (soton.ac.uk) Select programme type (Research), 2025/26, Faculty of Engineering and Physical Sciences, next page select “PhD Physics. (Full time)”. In Section 2 of the application form you should insert the name of the supervisor Prof Tim Freegarde

Applications should include:

Research Proposal

Curriculum Vitae

Two reference letters

Degree Transcripts/Certificates to date

For further information please contact: feps-pgr-apply@soton.ac.uk

The School of Physics. is committed to promoting equality, diversity inclusivity as demonstrated by our Athena SWAN award. We welcome all applicants regardless of their gender, ethnicity, disability, sexual orientation or age, and will give full consideration to applicants seeking flexible working patterns and those who have taken a career break. The University has a generous maternity policy, onsite childcare facilities, and offers a range of benefits to help ensure employees’ well-being and work-life balance. The University of Southampton is committed to sustainability and has been awarded the Platinum EcoAward.