Fabrication of silicon inverse woodpile photonic crystals

Silicon inverse woodpile photonic crystals are fabricated for the first time. Our approach, which is based on direct laser writing of polymeric templates and a novel silicon single-inversion procedure, leads to high-quality structures with gap/midgap ratios of 14.2%, centered at a wavelength of 2.5 mu m. It is shown that gap/midgap ratios as large as 20.5%, centered at 1.55 mu m, may become possible in the future.