Plasmonic metamaterials

A plasmonic metamaterial is a metamaterial that uses surface plasmons to achieve optical properties not seen in nature. Plasmons are produced from the interaction of light with metal-dielectric materials. Under specific conditions, the incident light couples with the surface plasmons to create self-sustaining, propagating electromagnetic waves known as surface plasmon polaritons (SPPs). Once launched, the SPPs ripple along the metal-dielectric interface. Compared with the incident light, the SPPs can be much shorter in wavelength. A plasmonic metamaterial is a metamaterial that uses surface plasmons to achieve optical properties not seen in nature. Plasmons are produced from the interaction of light with metal-dielectric materials. Under specific conditions, the incident light couples with the surface plasmons to create self-sustaining, propagating electromagnetic waves known as surface plasmon polaritons (SPPs). Once launched, the SPPs ripple along the metal-dielectric interface. Compared with the incident light, the SPPs can be much shorter in wavelength. The properties stem from the unique structure of the metal-dielectric composites, with features smaller than the wavelength of light separated by subwavelength distances. Light hitting such a metamaterial is transformed into surface plasmon polaritons, which are shorter in wavelength than the incident light. Plasmonic materials are metals or metal-like materials that exhibit negative real permittivity. Most common plasmonic materials are gold and silver. However, many other materials show metal-like optical properties in specific wavelength ranges. Various research groups are experimenting with different approaches to make plasmonic materials that exhibit lower losses and tunable optical properties. Plasmonic metamaterials are realizations of materials first proposed by Victor Veselago, a Russian theoretical physicist, in 1967. Also known as left-handed or negative index materials, Veselago theorized that they would exhibit optical properties opposite to those of glass or air. In negative index materials energy is transported in a direction opposite to that of propagating wavefronts, rather than paralleling them, as is the case in positive index materials. Normally, light traveling from, say, air into water bends upon passing through the normal (a plane perpendicular to the surface) and entering the water. In contrast, light reaching a negative index material through air would not cross the normal. Rather, it would bend the opposite way. Negative refraction was first reported for microwave and infrared frequencies. In 2007, a collaboration between the California Institute of Technology, and the NIST reported narrow band, negative refraction of visible light in two dimensions.