Negative-index metamaterial
![A negative-index metamaterial causes light to refract, or bend, differently than in more common positive refractive index materials.](/Images/godic/202501/24/Artist's_rendition_of_the_new_light-bending_metamaterial4802.jpg")
![A split-ring resonator array arranged to produce a negative index of refraction, constructed of copper split-ring resonators and wires mounted on interlocking sheets of fiberglass circuit board. The total array consists of 3 by 20×20 unit cells with overall dimensions of 10×100×100 millimeters.[4][5] The height of 10 millimeters measures a little more than six subdivision marks on the ruler, which is marked in inches.
Credit: NASA Glenn Research Center.](/Images/godic/202501/24/Split-ring_resonator_array_10K_sq_nm4802.jpg")
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![Refraction of light at the interface between two media of different refractive indices, with n2 > n1. Since the velocity is lower in the second medium (v2 < v1), the angle of refraction θ2 is less than the angle of incidence θ1; that is, the ray in the higher-index medium is closer to the normal.](/Images/godic/202501/24/Snells_law.svg4802.png")
Negative-index metamaterial or negative-index material (NIM) is a metamaterial whose refractive index for an electromagnetic wave can be determined and has a negative value over some frequency range.
NIMs are constructed of periodic basic parts called unit cells, which are usually significantly smaller than the wavelength. The unit cells of the first experimentally investigated NIMs were constructed from circuit board material, or in other words, wires and dielectrics. And in general, these artificially constructed cells are stacked or planar and configured in a particular repeated pattern to compose the individual NIM. For instance, the unit cells of the first NIMs were stacked horizontally and vertically, resulting in a pattern that was repeated and intended (see below images).