"Graphene nanophotonics: Smaller, stronger, faster"

Lead Research Organisation: University of Exeter
Department Name: Physics

Abstract

Understanding and controlling the interaction between light and matter is fundamental to science and technology - from probing entanglement in quantum physics to optical networks for information technology. Using traditional optics, light can only be controlled on length scales down to the wavelength of light, the classical diffraction limit. This limit has huge consequences, setting stringent boundaries for a host of phenomena. In recent years plasmonics has emerged as a means to beat this apparent limit. The key attribute of plasmon resonances, typically observed in nanoparticles of gold and silver, is the ability to concentrate optical energy into volumes well below the diffraction limit. This light focussing property gives rise to many potential applications, from photo thermal treatment of cancer to light harvesting in enhanced solar cells.

However, the field of plasmonics currently stands at a cross-road. The enormous potential of plasmonics as a means to manipulate light at the nanoscale is blocked by ohmic losses associated with the metals used; these losses ultimately set limits on light focussing and energy concentration. In this project I will explore a radical alternative by replacing conventional metals with new atomic scale, graphene-like layered materials. The ultimate goal is to overcome the critical limitations which currently hold plasmonics back, and thereby define future directions in the field. The three broad aims are:

(1) Smaller - I will study the fundamental limits of energy concentration in plasmonics. Efforts will concentrate on developing and optimising platforms in promising new plasmonic materials based on the atomically layered structure of graphene.
(2) Stronger - Energy concentration comes at a heavy price due to high absorption losses, which normally limits the plasmon lifetime to a few short femtoseconds. Recent results suggest absorption losses can be overcome by utilizing amplifying gain materials, which will enable active functionalities in these new plasmonic materials.
(3) Faster - Atomic scale materials will bypass the problems associated with absorption, and will transform our ability to manipulate light on ultrafast timescales. This has enormous consequences, with potential applications for switching and nonlinearity, both vital for information processing with light.

An ambitious plan is laid out, through which the vision of manipulating light on extreme sub-wavelength length scales will be made possible. This grand-scale project will unlock the true potential of ultrathin plasmonic materials for real-world photonic and optoelectronic devices.

Planned Impact

Developments in recent months have pointed towards nano-structured graphene as a ground-breaking new material in the field of nano plasmonics. This new material will allow us to push the boundaries in the fields of nanophotonics and plasmonics by controlling and even eliminating material losses. This research project will construct a foundation for using graphene as the backbone of optical and optoelectronic devices, with applications as diverse as light harvesting, photodetectors and optical sensing. Knowledge gained will be therefore be of intrinsic interest to the UK's electromagnetics and metamaterials research community, including those involved with the study of transformation optics and negative refraction. Our results will also feed into antenna and communication, imaging, anti-counterfeiting and homeland security applications.

In the later work packages, this project aims to demonstrate and develop several new tools and/or techniques for fundamental and applied research. Potential technologies under consideration in the final work package represent a radically new approach to well established, plasmon based sensing and analysis techniques. Once understood, the development of new sensing and spectroscopy techniques based on our discoveries could provide effective measurement tools for molecular materials, aimed primarily at the realms of biophotonics and life sciences. Some preliminary estimates based on estimates of modal volumes from the literature suggest that these tools could allow the ultrasensitive detection of biomaterial at the pictogram level, which may give rise to new types of measurement which were previously considered impossible. For example, one can envisage experiments to monitor protein dynamics in ultra-small (nanofluidic) volumes or the rapid assaying of molecular structure. In order to exploit this, I will fully engage with industry-facing platforms including the Technology Strategy Board's Electronics, Sensors, Photonics (ESP) Knowledge Transfer Network (KTN), and the MOD's Defence Materials Centre (of which Exeter is an active member). Through these organisations, I will commit to disseminate our findings to new networks, ensuring the sensing community is able to make the best use of our newfound knowledge in this sector, and to find fresh contacts and routes for partnerships. An important strand will be ensuring impact in the intellectual user community. I have significant experience in managing industrial relations, notably through industrial CASE awards jointly with QinetiQ (indeed, QinetiQ also have major involvement through Exeter's Knowledge Transfer Account "Tailored Electromagnetic Solutions" with the EPSRC). They will provide a technical point of contact for us to engage and interact with a view to exploiting our results.

The PDRAs and PhD students working with us will benefit through this highly multidiscipliunary project, both in terms of specific research skills and also in terms of work/project management. They will be expected to take an active role in collaborating with external colleagues. They will also be involved with knowledge transfer, intellectual property and commercial relations: training on all of these topics will be available through Exeter's RKT office. They will play a key role in giving presentations, ranging from regular intradepartmental meetings to commercial briefings and scientific workshops/conferences, and in writing publications/reports. These young researchers will therefore develop a unique and highly marketable skill set, with transferable skills generated at the interface between the physical sciences and engineering.

Publications


10 25 50
Beckerleg C (2016) Localized plasmons induced by spatial conductivity modulation in graphene in Journal of the Optical Society of America B
Constant T (2015) All-optical generation of surface plasmons in graphene in Nature Physics
Jensen S (2014) Terahertz Depolarization Effects in Colloidal TiO2Films Reveal Particle Morphology in The Journal of Physical Chemistry C
Mikhaylovskiy RV (2015) Ultrafast optical modification of exchange interactions in iron oxides. in Nature communications
 
Description We have shown that the highly nonlinear optical response of graphene can be utilized to generate surface plasmons. This is the first time that this has ever been shown, and we have recently published this in a high profile journal, Nature Physics.
Exploitation Route The results of this project are still very prelimenary, but already show promise for the development of brand new communications, optoelectronic and sensing technologies based on graphene plasmonics. Now that we have an efficient way of optically generating surface plasmons in graphene, a host of new directions are possible. We are currently working on excitation, propagation and detection experiments, which are the first tentative steps towards plasmon circuitry.
Sectors Digital/Communication/Information Technologies (including Software),Electronics
URL http://www.grasp-fet.eu/
 
Description Prelimenary results studying the relaxation kinetics of hot carriers are currently being applied in our group to improve sample quality and design. Our studies of the nonlinear response of graphene are driving ongoing theoretical studies as part of our FET network, GRASP. These collaborations are proving particularly fruitful, as we look to utilize graphene as a nonlinear medium of the future. We have recently held a workshop on this topic, attended by over 60 accademics from all over the world. Details can be found on our website: http://www.grapheneoptics2015.com
Sector Digital/Communication/Information Technologies (including Software),Electronics
 
Description FP7 FET grant
Amount € 395,000 (EUR)
Organisation European Research Council (ERC) 
Sector Public
Country European Union (EU)
Start 01/2014 
End 01/2017
 
Description ICFO 
Organisation ICFO - The Institute of Photonic Sciences
Country Spain, Kingdom of 
Sector Charity/Non Profit 
PI Contribution This partnership forms the basis of a FET european grant between groups at ICFO, Exeter, Berlin and Vienna, aimed at investigating the possibilities for single photon nonlinearities in graphene.
Collaborator Contribution Theory development and sample fabrication.
Impact Multidisciplinary: Theory - development of nonlinear optical models for graphene Sample Fab - fabrication of nanopatterned graphene devices
Start Year 2014