Next-generation mid-infrared spectroscopy with multifunctional photonic metasurfaces

Motivation: Mid-Infrared (MIR) spectroscopy is a powerful tool for identifying biochemical substances by their unique vibrational absorption signatures (wavelengths ~2-14 µm)—playing a crucial role in revolutionary technologies underpinning biomedical diagnostics, remote sensing, and environmental monitoring. Unfortunately, MIR spectroscopic sensing/ imaging is considered cumbersome, expensive and usually confined to the laboratory. Technological challenges remain for scaling-down traditional spectroscopy systems—from the light source, sensing mechanism (due to weak interactions), to the detection sub-system. Metasurfaces offer an exciting pathway towards next-generation multifunctional MIR sensing technologies. Metasurfaces are the 2D equivalent of 3D metamaterials: artificially engineered materials with properties impossible to find in nature. Photonic metasurfaces utilise nanoscale light-matter interactions within arrays of sub-wavelength structures (meta-atoms) to manipulate electromagnetic waves. However, conventional forward-design processes in photonics lead to limited final device functionality and inadequate performance, with no obvious way to proceed. AI-driven inverse-design approaches offer a new paradigm in photonic structure design overcoming traditional approaches. 

Project: This interdisciplinary PhD project will develop multifunctional photonic metasurfaces using inverse-design methods for unconventional MIR spectroscopic sensing and hyperspectral imaging technologies. The goal of this PhD is to have developed a family of next-generation MIR technologies. We will investigate, (1) thermal emission micro-sources which manipulate thermal emission beyond that of classical isotropic, broadband and unpolarized Blackbody emission; (2) enhancement of molecular vibrational absorption modes associated with target molecules (including glucose, in conjunction with industrial partner); (3) light-driven photothermal transducers for ultra-sensitive sensing.  

Skillset development: The research spans fundamental optical physics through to applications, and the student will develop a diverse and sought-after skillset during the PhD project, including: computational optics using AI / machine learning approaches, electromagnetic simulation (incl. Lumerical FDTD and COMSOL), nanofabrication within a state-of-the-art cleanroom (incl. e-beam lithography, physical vapour deposition and two-photon polymerization 3D printing), electro-optic systems characterisation, validation of sensing performance, and advanced data analysis. The project will leverage a EPSRC Core Equipment funded two photon polymerisation 3D printer to create novel micro-and-nanoscale structures.

Centre for Metamaterials Research & Innovation at the University of Exeter: The Department of Physics at Exeter has extensive expertise across optical physics, photonic device development and metamaterials. The student will have access world-class research facilities and be based within the Centre for Metamaterials Research and Innovation (CMRI): a community of academic, industrial, and governmental partners that harnesses world-leading research excellence from theory to application, and enables simulation, measurement, and fabrication of metamaterials and metamaterial-based devices. Dr. C. Williams (PI), based within the CMRI, develops novel imaging and sensing technologies based on engineering nanoscale light-matter interactions. 

About the Candidate: The successful candidate should be completing / have completed their undergraduate degree in Physics, Engineering or related Physical Sciences discipline (2:1 / above). They should be self-motivated, a creative problem solver, and with a strong interest in photonics, electromagnetism and computational optics. Strong analytical and experimental skills are essential. Proficiency in Python / MATLAB programming is desirable, and motivation for experimentally-focused research is preferred.

Funding and how to apply: The University of Exeter has a number of fully funded EPSRC (Engineering and Physical Sciences Research Council) Doctoral Landscape Award (EPSRC DLA) studentships for 2025/26 entry.  

Application Deadline: The closing date for applications is midnight (GMT) on 10th February 2025.  

How to apply: https://www.exeter.ac.uk/study/funding/award/?id=5480

Supervisor contact: For further information please contact Dr. Calum Williams: e-mail C.Williams15@exeter.ac.uk and website: https://physics-astronomy.exeter.ac.uk/staff/cw1037. Candidates are encouraged to contact Dr. Calum Williams to discuss the project before applying.