Negative Refractive Index Metamaterials

Superlens microscope gets up close. ‘The first direct near-field optical images from a superlens have been obtained by researchers in Germany and the US. Superlenses are made of negative refractive index metamaterials and this breakthrough could lead to their use in enhancing near-field microscopy for imaging biological samples and materials used in electronics (Science 313 1595). The resolution of conventional optical microscopes is restricted by near-field effects; as a result, they are unable to image objects below approximately a wavelength in size and this limits their use. This is because the near-field portion of the light – which contains the object’s sub-wavelength spatial details – decays or evanesces quickly with distance compared to the “far-field” portion, which is easily refocused by a conventional lens.’

The reality of negative refraction. ‘One of the most fundamental phenomena in optics is refraction. When a beam of light crosses the interface between two different materials, its path is altered depending on the difference in the refractive indices of the materials. The greater the difference, the greater the refraction of the beam. For all known naturally occurring materials the refractive index assumes only positive values. But does this have to be the case?’

Wikipedia: Metamaterial. ‘In electromagnetism (covering areas like optics and photonics), a meta material (or metamaterial) is an object that gains its (electromagnetic) material properties from its structure rather than inheriting them directly from the materials it is composed of. This term is particularly used when the resulting material has properties not found in naturally-formed substances. Metamaterials are promising for a diversity of optical/microwave applications, such as new types of beam steerers, modulators, band-pass filters, superlenses, microwave couplers, and antenna radomes.’

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