Giant birefringence is demonstrated in ensembles of randomly grown, vertically aligned semiconductor nanowires. Bottom-up fabrication of epitaxial semiconductor nanowires grown using the vapor-liquid-solid mechanism yields a highly anisotropic photonic metamaterial. The birefringence in the material is shown to depend on the nanowire length. Short nanowires with a volume filling fraction around 50% exhibit the strongest birefringence, in agreement with effective medium theories. A large difference is found between the in-plane and out-of-plane refractive indices of ?;n=0.8, exceeding by a factor of 75 the natural birefringence of quartz and by more than a factor of 2 that of inverted artificial materials.
Appl. Phys. Lett.

Muskens, O. L., Borgström, M. T., Bakkers, E., & Gómez Rivas, J. (2006). Giant optical birefringence in ensembles of semiconductor nanowires. Appl. Phys. Lett., 89(Article number: 233117), 1–3. doi:10.1063/1.2402906