Nonlinear plasmonic metamaterials that are resonant in the terahertz spectral range have been made from disks of indium arsenide. Huseyin Seren and co-workers in the USA fabricated these materials and note that nonlinear semiconductor plasmonic disks may be useful as optical limiters or saturable absorbers. The team used dry etching to fabricate hexagonal arrays of indium arsenide disks that are 70 micrometres in diameter. The samples were doped to a level of 1017 cm−3 resulting in a strong plasmonic response at 0.8 terahertz. A key advantage of using semiconductors as the plasmonic medium is that the doping level can be used to control the resonance frequency and other properties of the metamaterial.
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