New theoretical tools for metamaterial design

Lead Research Organisation: University of St Andrews
Department Name: Physics and Astronomy

Abstract

Imagine that we could control light to the extent that we can control electrons. The modern computer was developed thanks to our ability to control the flow of electrons through a circuit, and the magnetism of electrons in a hard disk. If we had the same influence over the behaviour of light then this could produce a similar revolution in technology; many everyday optical devices could be improved - projectors, fiber optic cabling, telescopes, microscopes, medical imaging units, and DVD players, are all limited by our control over light. The problem is that while electrons interact with external fields and each other, in normal circumstances photons do not. It is the purpose of this research to increase our control over light through improving the tools used to design a new class of optical materials known as metamaterials.Metamaterials have optical properties that are not found in naturally occurring media. To make a metamaterial involves the manufacture of an intricate composite structure, made out of insulating and conducting materials. This technology has allowed for the construction of a lens that can overcome the diffraction limit, and even an invisibility cloak: so far both of these devices have been shown to work in the microwave region of the spectrum. How is this `intricate composite structure' of a metamaterial determined? The surprising answer is that often, as far as light is concerned, the region of space occupied by a metamaterial behaves as if it were free space, but with a modified definition of what can be considered as a straight line . The curved path the light follows through a metamaterial device can be considered to be formally equivalent to the curved axes of a non-Cartesian system of co-ordinates, and this modified geometry is immediately related to the physical properties of the material. Find a geometry that has the `right straight lines' for a given optical function, and the required `intricate composite structure' of the metamaterial can then be computed: this procedure is the theory of `transformation optics'. The aim of this research is to pursue the initial goal - `to control light as well as we can control electrons' - through extending the reach of transformation optics to include new physics and new geometry. The more powerful we can make transformation optics, the greater the scope we have for metamaterial design, and the greater influence we can have over the behaviour of light. First we introduce new geometry;(1) At present, the optical materials considered within transformation optics are only equivalent to spaces that are stretched or curved relative to free space. Although this is a powerful theory in itself, it does not allow for another geometric property; torsion. Torsion represents the way a space is twisted. The project will generalise transformation optics to include spaces with torsion. This will add chirality into metamaterial design. A metamaterial that is equivalent to a space that twists vectors as they move along a co-ordinate axis would be expected to twist the vector properties of light as it moves through the material. Therefore adding torsion into transformation optics should allow for the design of new materials that manipulate the polarization of light.The second step is to introduce new physics;(2) Transformation optics is a classical theory of light interacting with matter, that reduces the problem to one of geometry. However, it contains remarkably few approximations. So we might therefore wonder the extent to which this picture is useful when quantum mechanics becomes important. Can we use transformation optics to design single photon metamaterial devices? The project will use an approximate quantum mechanical model for a metamaterial interacting with a quantized light field, and attempt to extend the procedure of transformation optics to the design of a new generation of devices in quantum optics.

Planned Impact

The non-academic beneficiaries of this work can be summarized as follows; (1) Photonics industry: Metamaterials are being used to create useful optical devices that are currently on the market (e.g. photonic crystal fibers). As the market grows it is expected that a much more general class of metamaterial based devices will be produced. The generalization of transformation optics obtained from this project will be a useful tool for designing devices that are sensitive to polarization. (2) Telecommunications infrastructure: With more efficient and effective optical components, the fiber optics based telecommunications infrastructure of the UK will be made more efficient. (3) Wider public: A more efficient communications network will mean that the cost of communication can be reduced, and that the energy required per unit of bandwidth will be lowered. Cheaper communication will benefit charities, businesses, government, and individuals, thus increasing the prosperity of the UK. The first substantial commercial applications of this project are most likely to be in the telecommunications industry. These applications would be expected to come after the diversification of the metamaterials market, which according to the report summarized in the Impact plan, is expected to be in around ten years. The communication of the project deliverables to the beneficiaries will be increased via, (1) Conferences & one day meetings with the involvement of knowledge transfer networks: Conferences, such as Photon10 (Photonics Knowledge Transfer Network), Metamaterials congress (IET Photonics Network), and one day meetings organised by the IoP groups detailed in the Dissemination & exploitation section conferences. (2) Publication: All pre-prints of academic publications will be made available to download. (3) Web material: A website will be produced that summarizes the research and makes the numerical work of the project available to use. I have experience as a first author, in presenting my work to a general audience, and in producing web pages. To increase the future impact of my work within industry I will also be, (4) Attending the industrial-academic interface postdoctoral workshops and training at St.Andrews.

Publications

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Horsley S (2012) Radiation pressure on a moving body: beyond the Doppler effect in Journal of the Optical Society of America B

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Horsley S (2014) Revisiting the Bragg reflector to illustrate modern developments in optics in American Journal of Physics

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Horsley S (2012) Radiation pressure in stratified moving media in Physical Review A

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Horsley SA (2013) Optical nonreciprocity of cold atom Bragg mirrors in motion. in Physical review letters

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Horsley SA (2011) Radiation damping in atomic photonic crystals. in Physical review letters

Related Projects

Project Reference Relationship Related To Start End Award Value
EP/H027610/1 24/05/2010 31/08/2012 £213,589
EP/H027610/2 Transfer EP/H027610/1 01/09/2012 31/05/2013 £51,613
 
Description (1) It was found that the theory of transformation optics (which is one of the main tools employed in metamaterial design) can be extended to include the geometrical property of torsion. As anticipated, this incorporates chiral metamaterials into the theory. This has been applied to some example systems, where it allows us to control the polarization of light in terms of a geometrical quantity.

(2) An extension of the Huttner-Barnett `damped polariton' model was found to understand some metamaterials materials from the perspective of a more fundamental theory. It was found that this theory naturally restricts the range of allowed material parameters, and we have used this to understand the bounds of possible new kinds of electromagnetic materials. Moreover - and unexpectedly - this theory shows quite clearly that metamaterials cannot fully mimic materials in motion. This sheds some light on the recent controversy of quantum friction.

(3) Motivated by the unanticipated finding that `damped-polariton' type models teach us something new and interesting about the quantum mechanics of moving media, the quantum theory of moving dielectrics was then investigated. Some quite surprising features of the quantum theory were found. For example, the Hamiltonian of a uniformly moving dielectric is unbounded from below. The theory of dielectric bodies moving through the quantum vacuum appears to be a promising area for further work.

(4) I have also been developing the ideas of transformation optics in the context of electromagnetic waves confined to surfaces. This has led to experiments and industrial collaboration with BAE systems and Queen Mary University/Exeter University. In particular we found that it is possible to conceal from surface waves objects that are placed on top of a surface.
Exploitation Route If industry starts to apply the ideas of transformation optics to the design of optical components (which is feasible, if optical computers become commercially available), then it may be useful to incorporate greater polarization control into the design process. (1) The extension to the theory of transformation optics that we found may be applied to design further devices.

(2) The restrictions on material parameters found may make it clearer what chiral and bianisotropic metamaterial parameters can be realised in practice.

(3) The theoretical work on the quantum mechanics of light in the vicinity of moving media may point the way to some exciting experiments to probe negative frequency modes of the vacuum.

(4) The work on cloaking with Queen Mary university and BAE systems may find a practical application in teh aerospace industry.
Sectors Aerospace, Defence and Marine,Digital/Communication/Information Technologies (including Software)

 
Description My findings have mainly been used for further research, but have also been applied in industry, with one particular device being manufactured by BAE systems. This is ongoing work with Queen Mary University. We are also continuing to experimentally investigate the theory I have developed in Exeter. Since the end of the grant we have continued to develop our theory of non-reflecting materials and have a PhD project with Thales to manufacture these materials
First Year Of Impact 2011
Sector Aerospace, Defence and Marine
 
Description Collaboration with European Laboratory for Nonlinear Spectroscopy (LENS) 
Organisation European Laboratory for Non-Linear Spectroscopy (LENS)
Country Italy, Italian Republic 
Sector Public 
PI Contribution Worked out theory for breaking optical reciprocity in cold atom systems/
Collaborator Contribution Discussions and help in understanding the theory. Links with experimental groups at LENS.
Impact Horsley SAR, Wu J-H, Artoni M, La Rocca GC. (2014) Revisiting the Bragg reflector to illustrate modern developments in optics, American Journal of Physics, volume 82, DOI:10.1119/1.4832436. Horsley SAR, Wu J-H, Artoni M, La Rocca G. (2013) Optical Nonreciprocity of Cold Atom Bragg Mirrors in Motion, Physical Review Letters, volume 110, DOI:10.1103/PhysRevLett.110.223602. Wu J-H, Horsley SAR, Artoni M, La Rocca GC. (2013) Radiation damping optical enhancement in cold atoms, Light: Science & Applications, volume 2, article no. e54, DOI:10.1038/lsa.2013.10. Horsley SAR, Artoni M, La Rocca GC. (2012) Radiation pressure in stratified moving media, Physical Review A - Atomic, Molecular, and Optical Physics, volume 86, no. 5. Horsley SAR, Artoni M, La Rocca GC. (2012) Radiation pressure on a moving body: Beyond the Doppler effect, Journal of the Optical Society of America B: Optical Physics, volume 29, no. 11, pages 3136-3140. Horsley SAR, Artoni M, La Rocca GC. (2011) Radiation damping in atomic photonic crystals, Physical Review Letters, volume 107, no. 4, DOI:10.1103/PhysRevLett.107.043602.
Start Year 2010
 
Description Collaboration with European Laboratory for Nonlinear Spectroscopy (LENS) 
Organisation University of Pisa
Country Italy, Italian Republic 
Sector Academic/University 
PI Contribution Worked out theory for breaking optical reciprocity in cold atom systems/
Collaborator Contribution Discussions and help in understanding the theory. Links with experimental groups at LENS.
Impact Horsley SAR, Wu J-H, Artoni M, La Rocca GC. (2014) Revisiting the Bragg reflector to illustrate modern developments in optics, American Journal of Physics, volume 82, DOI:10.1119/1.4832436. Horsley SAR, Wu J-H, Artoni M, La Rocca G. (2013) Optical Nonreciprocity of Cold Atom Bragg Mirrors in Motion, Physical Review Letters, volume 110, DOI:10.1103/PhysRevLett.110.223602. Wu J-H, Horsley SAR, Artoni M, La Rocca GC. (2013) Radiation damping optical enhancement in cold atoms, Light: Science & Applications, volume 2, article no. e54, DOI:10.1038/lsa.2013.10. Horsley SAR, Artoni M, La Rocca GC. (2012) Radiation pressure in stratified moving media, Physical Review A - Atomic, Molecular, and Optical Physics, volume 86, no. 5. Horsley SAR, Artoni M, La Rocca GC. (2012) Radiation pressure on a moving body: Beyond the Doppler effect, Journal of the Optical Society of America B: Optical Physics, volume 29, no. 11, pages 3136-3140. Horsley SAR, Artoni M, La Rocca GC. (2011) Radiation damping in atomic photonic crystals, Physical Review Letters, volume 107, no. 4, DOI:10.1103/PhysRevLett.107.043602.
Start Year 2010
 
Description Collaboration with Queen Mary Antennas group 
Organisation Queen Mary University of London
Country United Kingdom of Great Britain & Northern Ireland (UK) 
Sector Academic/University 
PI Contribution Worked out the theory for a cloaking device for surface waves.
Collaborator Contribution Modelled the designs, and involved industrial partners (BAE systems) in the manufacture of the cloaking device.
Impact R. C. Mitchell-Thomas, T. M. McManus, O. Quevedo-Teruel, S. A. R. Horsley, and Y. Hao, Phys. Rev. Lett. 111, 213901 (2013) - work done during the fellowship. T. M. McManus, J. A. Valiente-Kroon, S. A. R. Horsley and Y. Hao, Scientific Reports 4, Article number: 5977 (2014) - work done during the fellowship (a generalization of the above paper).
Start Year 2012
 
Description Collaboration with University of Exeter Experimental Group 
Organisation University of Exeter
Country United Kingdom of Great Britain & Northern Ireland (UK) 
Sector Academic/University 
PI Contribution Worked out transformation optics theory for surface wave experiments. This led into the EPSRC QUEST program.
Collaborator Contribution Performed the surface wave experiments.
Impact J. A. Dockrey, M. J. Lockyear, S. J. Berry, S. A. R. Horsley, J. R. Sambles, and A. P. Hibbins, Phys. Rev. B 87, 125137 (2013) S A R Horsley and I R Hooper 2014 J. Phys. D: Appl. Phys. 47 435103 (2014) (work done during fellowship, published afterwards)
Start Year 2012
 
Description Beacon lecture - how to build an invisibility cloak 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact Interesting discussions before and after talk. Stimulated the audience thinking about what is physically possible. Generated media attention (papers and radio interviews).

Contact from media organizations. Parents reported increased interest from their children.
Year(s) Of Engagement Activity 2012
URL http://www.st-andrews.ac.uk/news/archive/2011/title,77129,en.php
 
Description Royal Society of London Summer Science Exhibition (Invisibility) 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? Yes
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact Increased interest in invisibility science. Invitations for public lectures. Interesting discussion with members of the public who were not necessarily aware of the possibility of invisibility.

Invitations for public lectures.
Publicity (BBC, Guardian, blogs).
Year(s) Of Engagement Activity 2011
URL https://royalsociety.org/summer-science/2011/invisibility-science/
 
Description Royal society of Edinburgh Science exhibition 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? Yes
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact Interest from members of the public and the press.

Interest and further contact from members of the public. School demonstrations using our techniques.
Year(s) Of Engagement Activity 2012
URL http://www.royalsoced.org.uk/1028_April2012.html