Coupled plasmon resonances for sensing and active plasmonics

The dramatic progress in nanofabrications allows one to create new exciting composite plasmonic nanomaterials. These materials have attracted considerable interest as they offer a possibility to realise extraordinary electromagnetic properties important for optics, communications and electronics. Nanocomposite metamaterials also promise a whole variety of amazing applications, e.g., an optical lens beating the diffraction limit, a nanolens focusing light into a sub-wavelength spot, a supersensitive plasmonic nano-sensor, and active optical elements.

As in any "natural" material, coupling between "nano-atoms" and "nano-molecules" plays an important role allowing one to achieve new material properties and functionalities. Recently, we have experimentally observed several new interesting phenomena connected to coupling of localised plasmon resonances in plasmonic nano-arrays: i) quantized transparency of plasmonic arrays coupled by a thin conducting sub-layer ii) extremely narrow plasmon resonances produced by diffractive coupling iii) cascaded enhancements of electromagnetic fields produced by near-field coupling.

These findings are still under investigation and promise new exciting applications: ultra-sensitive plasmonic nano-sensors, extremely fast optical modulators and nano-focusing of light without lenses. The proposal aims to expand our initial findings into a viable research programme based on our current competitive advantage in exploration of coupled plasmon resonances. We will fabricate regular arrays of plasmonic nanomolecules and elucidate coupling mechanisms in all three cases. The main focus of our research will be 1) to engineer and fabricate plasmonic nanomaterials in which an optical response can be changed with the change of the coupling induced by graphene gating, 2) to elucidate the nature of diffractive coupled plasmon resonances and tailor nanomaterials for label-free plasmon nanosensors and 3) to study cascaded enhancement of electromagnetic fields. We plan not only to fabricate new optical composite nanomaterials and study their extraordinary electromagnetic properties but also to assess some of their applications, which we believe are the most promising and within our expertise (feasibility study of graphene based plasmonic optical modulator and plasmonic waveguide, phase sensitive nano-sensor, etc.).

Impact summary

Our results will be important first and foremost for the academic community. The theory of the collective plasmon resonances, quantized plasmonic will be useful for nanooptics and photonics. The new metamaterials based on regular arrays and plasmonic nanolenses will be stimulating and important for metamaterials community, scientists interested in bio- and chemical sensing. The last but not the least, the graphene-based plasmonic devices could useful for optoelectronics. We hope to widen understanding of the relevant physics, clarify the mechanisms of the studied effects and to check them by direct experiments.

The completion of the project would imply a fabrication of plasmonic devices which will be interesting for industry and technology. The ultra-sensitive sensors of based on phase sensitive plasmonic metamaterials will be useful for bio-technology and medicine. In principle, the suggested research can result in a cheap and reliable label-free alternative to labelling techniques for drug discovery. This alternative can be tempting for large pharmaceutical companies and fledging industries and can lead to benefits for the general public as far as health monitoring is concerned. It is worth mentioning that the phase sensitive SPR imaging suggested by the authors of the project is already marketed by Cambridge Consultant Inc in UK and one can envisage national commercial applications of the device prototypes developed during the course of the project. The cascaded nanolenses will be useful for the people who measure Raman signature of various substances.

The graphene-cased plasmonic devices (based on coupled plasmonic resonances) will be interesting to electronics companies as they promise cheaper and faster light modulation which can be used to increase internet speed and to improve the operation of the photocells. Hence public sector, business and industries, schools and the general public stand to benefit from the graphene based plasmonic research described in the proposal.

The impact of the project lies in 4 different areas.

1. The ontological impact. The acquired knowledge will be useful for scientific society and will provide with general insights into coupling of complex systems.

2. The economic impact. We hope that the device-prototypes demonstrated in the project will be useful for both large companies and for new industries as they promise to improve the drug monitoring and more effective energy harvesting. In addition to this it is possible to develop a 20x increase in internet speed with graphene-based modulators.

3. The health impact. The possibility to monitor drugs and pollutants using cheap and reliable plasmonic nanosensors and nanolenses will improve health awareness and allow people to do simple tests (e.g., blood type test) at home or work.

4. The technological impact. We will develop new technologies during the course of the project (e.g., nanolens fabrication, graphene blending with plasmonics, efficient plasmon coupling, creation a of 1D quantized resistive bridge) and will share our knowledge with interested parties, investigating the commercialization potential which arises.

New possibilities of using the collective plasmon modes (nanotweezing, active plasmonics, field amplifications) can lead to new foresights and result in more complex and smart materials.