Waveguides in three-dimensional photonic-bandgap materials by direct laser writing and silicon double inversion

Three-dimensional complete photonic-bandgap materials offer unique opportunities regarding the integration of optical waveguide architectures in three dimensions. However, corresponding experimental realizations are truly sparse. Here, we fabricate such waveguides using direct laser writing and a silicon double-inversion procedure. The optical characterization is in good agreement with theoretical calculations, raising hopes that even more complex architectures may soon come into reach.