Fabrication of three-dimensional photonic crystals using muitibeam interference lithography and electrodeposition

The fabrication of a high-quality 3D photonic crystal through electrodeposition into a polymer template created by multibeam interference lithography followed by removal of the template was demonstrated. The polymer template was fabricated on a conductive, transparent indium tin oxide (ITO)-glass substrate by exposing a negative-tone photoresist, SU-8, to superimposed interference beams over a spot size of 3 mm. The 3D pattern is found to have an fcc-like symmetry with shrinkage in the (111) direction, which is oriented perpendicular to the substrate. The polished photonic crystals exhibit stronger iridescence than the nonpolished one, suggesting that the rough top surface that scatters light could be removed and a flatter surface with a uniformly ordered structures is created. In the reflection spectra of the template, a peak is observed at 1.3μm, which is in agreement with the calculated position of the (111) stop band.