Biologically inspired photonic structures in Dichromated pullulan

We present properties of surface and volume photonic structures generated in Dichromated pullulan (DCP) using holographic technique. Volume Bragg gratings have properties of photonic crystals - wide bandgaps of the order of 100 nm. The bandgap is cantered at 560 nm at room temperature, and can be tuned with the substrate temperature to 480 nm at 100 °C. The process is reversible; bandgap goes back to 560 nm if substrate is cooled to 25 °C. Both surface and volume structure of DCP are complex: beneath structured surface there are porous, diffusing surface layer followed by the volume gratings. We have found that such structure resemblance structures found in nature. We present a detailed study of wings of two butterfly species Apatura iris (Linnaeus, 1758) and A. ilia with respect to their optical properties and the relationship of these properties to the microscopic structure of the wing scales. We are presenting also a close analogy between defects on the butterfly wing scales and fork-holograms used to generate vortex beams. We propose using pullulan for generation of butterfly like structures.