A Germanium inverse woodpile structure with a large photonic band gap

The first realization and characterization of a Ge inverse woodpile structure with a theoretical PBG width as large as 25 % was reported. To create a Ge inverse woodpile structure with the theoretical photonic properties, a polymer scaffold was produced by using direct-write assembly of a concentrated polyelectrolyte ink. A homogeneous fluidic ink (40 wt % polyelectrolyte in aqueous solution) was deposited into an alcohol-rich reservoir to produce a cylindrical filament approximately 1μm in diameter that is patterned in a layer-build sequence. Optical characterization was performed at each step of the fabrication process to characterize the optical response of the Ge inverse woodpile photonic crystals, and relate it to the properties of the initial polymer template. Combining simulation and experiment, a new route for creating three-dimensional complete bandgap photonic crystals at IR wavelengths was demonstrated.