About the Project
Supervisory team: Professor Callum Littlejohns, Dr Shengqi Yin, and Dr A. Emre Kaplan
Optical loss sets the performance limits of quantum, nonlinear and precision photonic circuits. This project will develop an ultra-low-loss silicon nitride platform by linking loss mechanisms to fabrication and device design. Validated components and models will support reproducible high-Q resonators and advanced quantum computing applications.
Ultra-low-loss silicon nitride (SiN) photonics enables long optical interaction lengths and high-Q resonators, supporting quantum light generation, nonlinear frequency conversion and precision sensing. Achieving these capabilities reproducibly requires control of material absorption, scattering and fabrication variability.
This project aims to establish an ultra-low-loss SiN platform supported by validated fabrication processes and predictive device models. The central objective is to determine how material properties, waveguide geometry and processing conditions govern propagation loss and resonator performance.
The research will combine optical modelling, fabrication studies and experimental characterisation to distinguish the contributions of sidewall roughness, material absorption and device geometry. Process and design variations will be evaluated systematically to identify routes to lower loss and quantify their reproducibility. Waveguide and resonator measurements will connect fabrication parameters to propagation loss, quality factor and device variability.
These results will inform a process design kit (PDK) library containing high-Q resonators, with more than 1 million Q-factor, delay lines and filters, with models that incorporate measured performance and fabrication tolerances. A selected quantum, nonlinear or sensing demonstrator will test whether component-level improvements translate into application-level benefits.
The expected contribution is a quantitative understanding of loss mechanisms, a reproducible fabrication approach and a validated library of low-loss photonic building blocks. Together, these outcomes will establish a reusable foundation for quantum, nonlinear and precision photonic circuits.
Comprehensive training will be provided in photonic and optical modelling using Ansys Lumerical, COMSOL Multiphysics and Zemax, alongside full equipment training in the University of Southampton's cleanroom facilities. You'll also receive hands-on training in optical measurements and silicon photonic chip testing, including optical alignment, fibre-to-chip coupling and device characterisation. Together, these activities will develop the skills required to design, fabricate and experimentally validate integrated photonic devices.
The School of Optoelectronics (ORC) 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.
Entry requirements
A UK 2:1 honours degree, or its international equivalent, in physics or a closely related discipline.
Fees and funding
We offer a range of funding opportunities for both UK and international students. Horizon Europe fee waivers automatically cover the difference between overseas and UK fees for qualifying students.
Competition-based Presidential Bursaries from the University cover the difference between overseas and UK fees for top-ranked applicants.
Competition-based studentships offered by our schools typically cover UK-level tuition fees and a stipend for living costs for top-ranked applicants.
Funding will be awarded on a rolling basis, so apply early for the best opportunity to be considered.
For more information, please visit our postgraduate research funding pages.
How to apply
You need to:
- choose programme type (Research), 2027/28, Faculty of Engineering and Physical Sciences
- select Full time or Part time
- search for programme PhD ORC (7097)
- add name of the supervisor in section 2 of the application
Applications should include:
- your CV (resumé)
- 2 academic references
- degree transcripts and certificates to date
- English language qualification (if applicable)
Contact us
Faculty of Engineering and Physical Sciences
For questions about applying, doctoralcollege-admissions@soton.ac.uk.
Project leader
For an initial conversation, C.Littlejohns@soton.ac.uk.
