Fabrication of uniform large-area polymer 'woodpile' photonic crystals structures with nanometer-scale features

We demonstrate a process to fabricate highly uniform large-area polymer 3-D "woodpile" photonic crystal structures with nanometer-scale features. This fabrication process utilizes the SU-8 resist's enhanced absorption of deep-UV wavelengths to achieve resist exposure confinement to a desired depth. It also uses the high resistance of cross-linked SU-8 resist to solvents for layer-upon-layer resist application and processing. This fabrication method affords the flexibility of incorporating arbitrary design patterns for the different layers. Depending on the exposure mask area and the size of exposure window available in the mask aligner, this fabrication process can provide such devices over wafer-scale areas. This fabrication method is highly compatible with standard semiconductor processing methods and is thus well suited for mass fabrication.