A novel class of optical metamaterials is presented consisting of high densities of aligned gallium phosphide (GaP) nanowires fabricated using metal-organic vapor phase-epitaxy. Starting from a gold island film as a catalyst for nanowire growth, a sequential combination of vapor-liquid-solid and lateral growth modes is employed to obtain a continuous tunability of the nanowire volume fraction from 7% to over 35%. By choosing different crystallographic orientations of the GaP substrate, metamaterials are designed with different nanowire orientations. The anisotropy of the nanowire building blocks results in strong optical birefringence. Polarization interferometry demonstrates a very large polarization extinction contrast of 4 × 103 combined with a sharp angular resonance which holds promise for optical sensing. Nanowire metamaterials may find applications in photonics, optoelectronics, non-linear and quantum optics, microfluidics, bio-, and gas sensing.

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Adv. Funct. Mater.

Muskens, O. L., Diedenhofen, S. L., van Weert, M. H. M., Borgström, M. T., Bakkers, E., & Gómez Rivas, J. (2008). Epitaxial growth of aligned semiconductor nanowire metamaterials for photonic applications. Adv. Funct. Mater., 18, 1039–1046. doi:10.1002/adfm.200701337