eli5: What is a negative-index metamaterial
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A negative refractive index meta material is a special type of material designed to have a negative index of refraction. A meta material is an engineered material which has properties not found in nature, all natural materials have a positive index of refraction which describes how light bends when it hits the material. When light transfers between two mediums you get refraction which changes the angle of the light. When the refractive index of the second material is higher than that of the first the light will bend towards being perpendicular with the surface and vice versa. Air for example has a refractive index of close to 1, when light goes from air to glass it gets bent towards the perpendicular line (the normal) and when it goes from glass to air it gets bent away. A negative index metamaterial has a refractive index of less than 0. This means that even light hitting it in a vacuum would be bent away from the normal line. This property allows for some really interesting optics and may let’s us build ‘super lenses’ with higher resolutions than allowed be conventional objects. However refractive index varies with the wavelength of light, as of now most of these materials only have negative refractive indices in the radio or microwave range rather than visible light.
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