University of Exeter funding: Manipulating the coupling and scatt

EPSRC CDT in Metamaterials (PhD studentship): Manipulating the coupling and scattering between surface waves and plane waves on metasurfaces, and at their discontinuities Ref: 3446

About the award

The studentship is part of the UK’s Centre of Doctoral Training in Metamaterials (XM2) based in the Departments of Physics and Engineering on the Streatham Campus in Exeter.  Our 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.

The 4 year studentship is funded 50:50 by an industrial sponsor and the College of Engineering, Mathematics and Physical Sciences at the University of Exeter. It is of value around £105,000, which includes £13,000 towards the research project (travel, consumables, equipment etc.), tuition fees, and an annual, tax-free stipend of approximately £16,500 per year for UK/EU students.

Eligible candidates: UK/EU nationals only due to industry sponsor requirements.

Exeter has a well-established and strong track record of relevant research, and prospective students can consider projects from a wide variety of fields:

  • Acoustic and Fluid-dynamical Metamaterials
  • Biological and Bio-inspired Metamaterials
  • Graphene and other 2D Materials, and related Devices
  • Magnonics, Spintronics and Magnetic Metamaterials
  • Microwave Metamaterials
  • Nanomaterials and Nanocomposites
  • Optical, Infra-red and THz Photonics and Plasmonics
  • Quantum Metamaterials
  • Wave Theory and Spatial Transformations

Please visit www.exeter.ac.uk/metamaterials to learn more about our centre and see the full list of projects that we have on offer this year.

The studentship is subject to funding availability.

Statement of Research

Joint supervisors: Prof Alastair P Hibbins, Prof J Roy Sambles

External supervisor: Prof Richard Craster (Imperial College London)

External partner: MBDA

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 XM2

Metamaterials are fabricated microstructures having properties beyond those found in nature. They are an important new class of electromagnetic and acoustic materials with applications in many technology areas: energy storage and improved efficiency, imaging, communications, sensing and the much-hyped ‘cloaking’. Having recruited over 80 PhD researchers since 2014, the EPSRC Centre for Doctoral Training (XM2) (www.exeter.ac.uk/metamaterials) will admit the next cohort of PhD students in September 2019.

The first year of the studentship includes an assessed, stand alone project, and a substantial programme of training. Students will choose from a wide range of taught modules, and participate in academic and personal development skills-based workshops, together with creativity events and conference-style meetings. The cohort will also be expected to disseminate their results to the international community via high-impact publications and international conferences. They will spend time working with our academic and industrial partners.  Full details of the programme are available here, or download a copy of our prospectus.

The University of Exeter combines world class research with excellent student satisfaction. It is a member of the Russell Group of leading research-intensive universities. Formed in 1955, the University has over 20,000 students from more than 130 different countries. Its success is built on a strong partnership with its students and a clear focus on high performance. Recent breakthroughs to come out of Exeter's research include the identification and treatment of new forms of diabetes and the creation of the world's most transparent, lightweight and flexible conductor of electricity. Exeter is ranked amongst the UK’s top 10 universities in the Higher Education league tables produced by the Times and the Sunday Times. It is also ranked amongst the world’s top 200 universities in the QS and Times Higher Education rankings.

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.

  • Degree transcript(s) giving information about the qualification awarded, the modules taken during the study period, and the marks for each module taken.
  • 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*:
    • 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;
    • Describe the qualities that you believe will make you a great researcher (in particular as part of a team).

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

Applications will normally be reviewed within two weeks of receipt from February 2019.
Candidates will be short-listed against a set of agreed criteria to ensure quality while maintaining diversity. Failure to include all 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).

Interviews

Shortlisted candidates will be invited to an entry interview to assess fit to the CDT concept. This will be held prior the academic interview with the supervisors and will normally be undertaken by a panel of 3 people, including a current postgraduate researcher or post-doc in Physics or Engineering.

Interviews are expected to start in February 2019. It is therefore advisable to apply as soon as possible.

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:Approximately £105,000, including research and travel budget, tuition fees and annual tax-free stipend (approx. £16,500 per year payable to UK or EU students only).
Duration of award:per year
Contact: Prof. Alastair Hibbins (Admissions Tutor) metamaterials@exeter.ac.uk