User:RHaworth/sb2
Plasmonic metamaterials are negative index metamaterials that exploit surface plasmons, which 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 and do not stray from this narrow path. Compared with the incident light that triggered the transformation, the SPPs can be much shorter in wavelength.[1]
Plasmonic metamterials are tailor made composites - combinations of materials designed to achieve optical properties not seen in nature. The properties stem from the unique structure of the composites, with features smaller than the wavelength of light separated by subwavelength distances. By fabricating such metamaterials fundamental limits tied to the wavelength of light are overcome. Light hitting a metamaterial is transformed into electromagnetic waves of a different variety—surface plasmon polaritons, which are shorter in wavelength than the incident light. This transformation leads to unusual and counterintuitive properties that might be harnessed for practical use. Moreover, new approaches simplify the fabricatrication process of metamaterials are under development This work also includes making new structures specifically designed to enable measurements of the materials novel properties. Furthermore, nanotechnology applications of these nanostructures are currently being researched, including microscopy beyond the diffraction limit.
Plasmonic materials
Plasmonic materials are composed of metals and dielectrics that are ordered in geometric arrangements with dimensions that are fractions of the wavelength of light. Research groups are experimenting with a variety of geometric approaches in an effort to exploit surface plasmons, which are light-induced packets of electrical charges that collectively oscillate at the surfaces of metals at optical frequencies. 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 and do not stray from this narrow path. Compared with the incident light that triggered the transformation, the SPPs can be much shorter in wavelength.
Negative index materials
Plasmonic metamaterials are incarnations of materials first proposed by a Russian theorist in 1967. Also known as left-handed or negative index materials, the proposed materials were theorized to exhibit optical properties opposite to those of glass, air. These have been termeed positive index—materials of our everyday world. In particular, energy is transported in a direction opposite to that of propagating wavefronts, rather than traveling in lockstep, as is the case in positive index materials. As a result, when juxtaposed with a positive index material, negative index materials were predicted to exhibit counterintuitive properties, like bending, or refracting, light in unnatural ways.[2]
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 beaming from air toward a negative index material would not cross the normal. Rather, it would bend the opposite way, and, as yet, not occuring in nature.
Negative refraction was first reported for microwaves and infrared radiation. In 2007, a collabroation team consisting of the Harry Atwater team at the California Institute of Technology, and the NIST reported narrow band, negative refraction of visible light in two dimensions.[2]
To accomplish this a material platform that is a sandwich-like construction with exceedingly thin layers was fabricated. It consists of an insulating sheet of silicon nitride topped by a film of silver and underlain by gold. The critical dimension is the thickness of the layers, which taken together are only a fraction of the wavelength of blue and green light. By incorporating this metamaterial into integrated-optics on an IC chip, negative refraction was demonstrated over blue and green frequencies. The design exploits bulk materials properties of each component, but the collective result is a relativley signifigant response to light.[2]
To create this response incident light couples with the undulating, gas-like charges normally on the surface of metals. This photon-plasmon interaction results in SPPs that generate intense, localized optical fields. The waves are confined to the interface between metal and insulator. This narrow channel serves as a transformative guide that, in effect, traps, squeezes, and compresses the wavelength of incoming light.[2]
Refs
<references>
- ^ Kuttge, M.; Vesseur, E.; Koenderink, A.; Lezec, H.; Atwater, H.; García De Abajo, F.; Polman, A. "Local density of states, spectrum, and far-field interference of surface plasmon polaritons probed by cathodoluminescence" (PDF). Physical Review B.
{{cite journal}}: Unknown parameter|svolume=ignored (help) - ^ a b c d Lezec, H. J.; Dionne, J. A.; Atwater, H. A. (2007). "Negative Refraction at Visible Frequencies" (PDF). Science. 316 (5823): 430. PMID 17379773.