Negative Refraction in Semiconductor Metamaterials

An optical metamaterial is a composite in which subwavelength features, rather than the constituent materials, control the macroscopic optical properties of the material. Whereas nature appears to have limits on the type of materials that exist, newly invented metamaterials are not bound by such constraints. Recently, optics researchers have been fascinated by the prospects of “left-handed” metamaterials, which show a negative index of refraction, whereas naturally occurring materials have positive index of refraction. The result is that light bends “backwards” upon entering a left-handed material, rather than continuing forward (see figure). This behavior has significant potential for optical components such as lenses for magnification and imaging.

Princeton’s new metamaterial is three-dimensional, which makes it useful for real-world optical components; it has relatively low optical loss; it is composed entirely of semiconductor materials grown epitaxially, and hence is straightforward to manufacture; finally, the new metamaterial functions over a very wide range of mid-infrared wavelengths, important for sensing applications.