Optical metamaterials are typically of intricate design, containing complex subwavelength metallic structures such as split rings or parallel bars; these structures are then periodically repeated in a lattice in attempts to achieve both negative permittivity and permeability, and thus negative refraction. Now, researchers at Princeton University (Princeton, NJ), Oregon State University (Corvallis, OR), and Alcatel-Lucent (Murray Hill, NJ) have created a much simpler structure that achieves negative refraction: alternating layers of semiconductors. Requiring only an anisotropic dielectric function with a single resonance, the structure operates in the long-wave IR region.
The metamaterial contains interleaved planar layers of indium gallium arsenide (In0.53Ga0.47As) and aluminum indium arsenide (Al0.48In0.52As) 8.1 µm thick on an InP substrate, with the InGaAs doped at different concentrations for different samples. Reflection and transmission measurements, such as with a focused spot and a knife-edge blade, using light longer than 8.8 µm show negative refraction, with the spectral bandwidth for the best sample being 27%. Loss was 1800 cm-1 at 40º incident angle and 2100 cm-1 at 60º. Contact Anthony Hoffman at [email protected].