Metamaterials are artificially engineered periodic structures with exceptional optical properties that are not found in conventional materials. They are built from individual elements, designed to mimic the electromagnetic response of atoms. Stacking many nano-engineered elements smaller than the wavelength of light makes new solid materials. Such materials have extremely unusual properties, such as negative refractive indices to focus light much smaller than its wavelength (super-lensing), or electromagnetic cloaking (of an object). The alliance of metamaterials with the fields of plasmonics, nanophotonics and nanofabrication technologies can further advance the possibility of controlling light propagation, radiation, localization and scattering in in unprecedented ways.
The development of metamaterials results in a series of intriguing applications, such as a cloak of invisibility, giant optical chirality, wave-front control, surface plasmon manipulations, as well as antennas of compact sizes and enhanced directionalities. Also, research has begun to shift focus, and scientists are now looking to achieve tunable, switchable, nonlinear and sensing functionalities using metamaterials. The rise of metamaterials is providing a new generation of ultrafast, deeply sub-wavelength, integratable nanophotonic devices and systems.
Recently, metamaterials have extended adding quantum elements such as quantum dots, cold atoms, Josephson junctions, and molecules. They exhibit controllable quantum states, maintain quantum coherence for times much higher than the transversal time of the electromagnetic signal. These metamaterials have been used to realised invisibility cloaking, super-resolution, energy harvesting, and sensing. Plasmene is a such kind of highly ordered and tightly-packed two-dimensional sheets of metal nanoparticles. The unique plasmonic and mechanical properties of plasmene nanosheets can be utilized for various technical applications including mechanical resonator, surface-enhanced Raman scattering (SERS) substrate, drug identification and anti-counterfeit security label.