Fabrication of a photonic crystal is described. A patterned array of nanowires is formed, the nanowires extending outward from a surface, the nanowires comprising a catalytically grown nanowire material. Spaces between the nanowires are filled with a slab material, the patterned array of nanowires defining a patterned array of channels in the slab material. The nanowire material is then removed from the channels.