Engineering stop gaps of inorganic-organic polymeric 3D woodpile photonic crystals with post-thermal treatment

A method is reported for improving the spatial resolution and engineering the stop gaps of the inorganic-organic 3D woodpile photonic crystals (PhCs). The approach is based on the two-photon polymerization (2PP) of an inorganic-organic hybrid material and a post-thermal treatment (PTT) process. The effects of PTT on polymerized ID, 2D and 3D structures have been characterized. Ultimately, the feature size of the suspended rods has been reduced to ∼33 nm and the spatial resolution of inorganic-organic 3D woodpile PhCs has been improved from -150 nm to -86 nm. The approach is also demonstrated as a powerful tool to engineer the stop gaps of 3D PhCs. In particular, a combination of PTT and the threshold fabrication technique leads to the stop gap of a 3D woodpile PhC that can be tuned over a large wavelength range of -318 nm from the near-infrared to visible region.