Unnatural manipulation of light
The unique properties of metamaterials stem from structural periodicity on much smaller scales than the wavelength of the light propagating through them. Microwave applications (wavelengths on the scale of one to 100 centimetres) are currently in a pre-commercial stage. Realising devices in the visible range (structures on the scale of nanometres) such as invisibility cloaks presents a serious fabrication challenge. For the first time, EU-funded scientists in nanochemistry, self-assembly and metamaterials joined forces on the project 'Nanochemistry and self-assembly routes to metamaterials for visible light' (METACHEM) . The goal was to provide a simple, low-cost manufacturing alternative to nanolithography. They also devoted great effort to developing measurement methods required to demonstrate concept validity. The team designed and synthesised tailor-made nanoparticles as optical plasmonic nanoresonators. These are surface plasmon-based structures exploiting the coherent bound oscillations of electrons and light at a metal surface. They were organised through self-assembly into dense, highly structured two- or three-dimensional networks. Plasmonic metamaterials have been difficult to fully exploit due to losses. Scientists addressed this issue in the conventional way, using loss-compensating active-gain media. A number of applications including advanced sensors, plasmonic nanoreactors and metamaterials with refractive indices not seen in nature were proposed. Knowledge and outcomes were disseminated through the project website, a training workshop, participation in international conferences and several brochures. The project also organised and participated in the Metamaterials’2013 International Conference as well as in a follow-up doctoral course. METACHEM has provided a turbo-boost to exploitation of plasmonic metamaterials. Scientists demonstrated that metamaterials can be produced by low-cost bottom-up self-assembly methods. With increased efficiency through compensation of losses, the team addressed one of the most important barriers to real applications. Finally, advances highlighted their potential as components of sensors, nano-chemical reactors, novel electromagnetic devices and many more, spawning exciting new avenues of research.
Keywords
Metamaterials, visible, fabrication, self-assembly, nanolithography, plasmonic, losses, active-gain
