Photonic band-gap structures of core-shell simple cubic crystals from holographic lithography

We report the investigation of photonic band-gap properties of a core-shell simple cubic structure (air core with a dielectric shell) using a two-parameter level-set approach. The proposed structure can be obtained by partially backfilling high refractive index materials into a polymeric template fabricated by multibeam interference lithography. We find that the shell formation in the inverted simple cubic structure increases the complete photonic band-gap width by 10%-20% in comparison to that of a completely filled structure. The band gap between the fifth and sixth bands begins to appear at a refractive index contrast of 2.7. This study suggests the importance to investigate the core-shell formation in three-dimensional photonic crystals through backfilling, which may offer an additional control over their photonic band-gap properties.