Manipulating the coupling and scattering between surface waves and plane waves on metasurfaces, and at their discontinuities (PhD in Physics/Engineering) Ref: 3399

About the award

This project is a 3.5 year long PhD studentship* which will cover UK tuition fees, an annual tax-free stipend at the UKRI minimum doctoral level (£14,777 per year for 2018), plus a Research and Training Support Grant (RTSG) of £1,500*.

*To note:

We are currently awaiting a decision from EPSRC regarding an application for a Centre for Doctoral Training in Functional and Meta- Materials (2019-2027) which will build on our expertise in Doctoral Training gained through the CDT in Metamaterials (XM²) since 2014.  The successful applicant will join the new CDT programme if Exeter succeeds in its bid. A funding decision is expected by January 2019.

However, the studentship will be funded regardless of the outcome.

For eligible students (UK nationals only due to industry partner requirements) the 4 year studentship (value approx. £102,000) will cover UK tuition fees, plus an annual tax-free stipend at the UKRI national minimum doctoral level, enhanced by £2,250 per year (£17,027 for 2018), or pro rata for part-time study, plus a Research and Training Support Grant (RTSG) of £13,000.

XM² now has over 80 post graduate researchers.  Its aim is to undertake world-leading research, while training scientists and engineers with the relevant research skills and knowledge, and professional attributes for industry and academia.

Please visit www.exeter.ac.uk/metamaterials for more information about the current CDT and an indication of what to expect.

UK/EU nationals only.

This studentship will be based on the Streatham Campus in Exeter. 

Joint supervisors: Prof Alastair Hibbins, Prof Roy Sambles, Prof Richard Craster (external, Imperial College London)

External partners: MBDA

Statement of Research

This project will explore the coupling of incident microwave radiation into surface waves, and also the reverse process: the reradiation of surface waves into free-space radiation. We will employ experimental, analytical and numerical (e.g. finite element method) techniques.

Surfaces patterned with a sub-wavelength scale elements (metasurfaces) can often be described using reactive boundary condition (either inductive or capacitive) that defines an effective skin depth that supports bound waves.

The impedance is determined by the geometry of the elements comprising the surface, and therefore frequency-dependent. The modes supported are inherently broad-band in nature, typically existing from DC up to a limit dictated by a geometric resonance of the elements that form the pattern.

Once excited, they are non-radiative on a planar surface, propagating over many tens or hundreds of wavelengths, only decaying via joule-heating or loss in the surrounding dielectric, or reradiating by diffraction at discontinuities or through surface curvature. Careful design of the shape, spacing and size of the surface elements allows manipulation of the flow of energy across the array, in terms of the direction, speed, loss and localisation of the mode.

Similarly the careful design of defects in the surface can yield strong coupling between free space radiation and the surface-bound energy. In this project, the student will study the scattering (i.e. radiation into free space) and the reflection of surface waves at and from defects and discontinuities.

We will study how grading of the surface impedance can reduce this effect, e.g., through variation of the geometry of patterning, or the addition of tapered overlayers. Outcomes may include efficient conversion of surface waves into plane wave radiation, or perfect absorption of surface wave energy. In parallel, we shall consider how to design surface structures to enable efficient excitation of surface waves.

Together, these two methodologies will yield a surface that converts incident radiation into surface waves over a broad bandwidth, which then decay to heat without further reradiation. We will explore theoretical ideas such as those involving the mathematics of topology [1] to design surfaces that constrain wave propagation to only one direction.

We will consider 'dispersion engineering' by exploiting non-local (spatially dependent) boundary conditions [2] to optimise the bandwidth over which efficient coupling can be achieved.

We will also investigate how reinterpretation of the Kramers-Kronig relations in the spatial domain can supress reflection of surface waves [3].

Literature

1. Yang et al., ‘Direct observation of topological surface-state arcs in photonic metamaterials’ Nature Communications 8:7 (2017).

2. Chasnitsky et al., 'Broadband surface plasmon wave excitation using dispersion engineering' Optics Express 23, 30570 (2015).

3. Horsley et al., 'Spatial Kramers–Kronig relations and the reflection of waves' Nature Photonics 9, 436 (2015).

About us 

Exeter has a well-established and strong track record in functional materials and metamaterials research, spanning a unique mix of interests in our focus areas:

  • Acoustic, Phononic and Fluidic Metamaterials
  • Microwave and RF Metamaterials and Devices
  • Nanocomposites and Manufacturing
  • Photonic and Plasmonic Materials
  • Soft Matter, Biomaterials and Sensors
  • Spintronics, Magnonics and Magnetic Materials
  • Theory and Modelling to drive Targeted Material and Device Design
  • Two Dimensional Electronic and Photonic Materials

Exeter is amongst the top 150 universities worldwide according to the Times Higher Education World University Rankings, the most influential global league table.
Functional Materials (from fundamentals to manufacturing) is one of 5 key themes supported by the UoE as part of its £320 million Science Strategy investing in staff and facilities. This theme has benefitted from the appointment of 23 new academics (including 7 full professors) along with £20m of investment in research infrastructure (including 3 new electronics/photonics clean-rooms, a graphene engineering laboratory, a nano-functional materials fabrication suite, a materials characterisation suite).

This is in parallel to significant external capital investment in our research including over £2m of equipment funding from the EPSRC/HEFCE SIA award (Exeter-Bath Centre for Graphene Science), the £2.6m ERDF-EADS funded Exeter Centre for Additive Layer Manufacture (CALM); £1.1, for Exeter’s EPSRC Time-Resolved Magnetism Facility; £1.2m for equipment funding from the EPSRC Graphene Engineering Call. Such investments ensure that we have, in-house, all the state-of-the-art materials, fabrication and characterisation facilities required by our PGRs.

Our research and PhD training experience, expertise, facilities and network makes the University of Exeter one of the very best places to pursue postgraduate and early career research.

How to apply

Application criteria

Eligible applicants: UK/EU nationals only.

During the application process you will need to upload the documents listed below. Please prepare these before starting the application process.

  • An academic CV;
  • A cover letter outlining your research interests in general, the title of the project you are applying for;
  • A Personal Statement consisting of two parts*:
  1. Describe a) why you would like to study for a PhD, b) why you would like to focus on this particular topic, c) any relevant expertise and d) your future career ambitions;

  2.  Describe the qualities that you believe will make you a great researcher (in particular as part of a team).

  • Degree transcript(s) giving information about the qualification awarded, the modules taken during the study period, and the marks for each module taken.

You will be asked to provide the contact details of two academic referees.

* We foster creativity and utilisation of individual strengths. Applicants are encouraged to provide evidence to support their statements. This might include conventional written documents (e.g. examples of work), but we also encourage alternatives such as audio or video recordings, websites, programming etc. Please ensure to include accessible links to such files in an appropriately named document as part of the upload process.


Application procedure

Shortlisting and interviews

Applications will be reviewed by at least two academic members of staff.

Candidates will be short-listed against a set of agreed criteria to ensure quality while maintaining diversity. Failure to include all the the elements listed above may result in rejection.

The essential criteria:

  •  Undergraduate degree in a relevant discipline (minimum 2:1);
  •  Vision and motivation (for research & professional development);
  •  Evidence of the ability to work collaboratively and to engage in a diverse community;
  •  Evidence of excellent written and oral skills in English.

The highest quality candidates will also be able to demonstrate one of more of the following:

  • Specialist knowledge about one or more of the 8 research areas listed above;
  • Training in research methodology (e.g. undergraduate research projects);
  • Research outputs (e.g. papers) and/or other indicators of academic excellence (e.g. awards).

Shortlisted candidates will be invited to an academic interview with the project supervisors.

To note: If the University of Exeter is successful with its proposal for an EPSRC-funded Centre of Doctoral Training in Functional and Meta-Materials an entry interview to assess fit to the CDT concept will be held prior the academic interview which will normally be undertaken by a panel of 3 people, including members of the CDT's Strategic Leadership Team and a current postgraduate researchers or post-doc in Physics or Engineering.

Interviews are expected to start in the second half of January 2019.

Please email metamaterials@exeter.ac.uk if you have any queries about this process.

Summary

Application deadline:30th April 2019
Number of awards:1
Value:Approx. £68,000 for 42 months (pro-rata for part-time study): covers UK/EU tuition fees, an annual tax-free stipend at the UKRI national minimum doctoral level (£14,777 per year for 2018), plus £1,500 RTSG. UK/EU nationals only.
Duration of award:per year
Contact: Prof. Alastair Hibbins (Admissions Tutor) metamaterials@exeter.ac.uk