Setae of the polychaete worm Pherusa exhibit remarkably strong photonic effects, which arise from their two-dimensional-periodic internal structure of hexagonally packed cylindrical channels. The hexagonal order is limited to monocrystalline domains of different orientation, which results in an overall polycrystalline effect. A detailed experimental and theoretical investigation of this structure reveals that the internal photonic structure is carefully tuned with respect to its lattice constant in order to provide an optical response coinciding with the visible wavelength rage. A further optimization is observed for the packing fraction of cylindrical channels in order to maximize the width of photonic band gaps, and hence the reflectance of incident visible light.

• Received 21 July 2009

DOI:https://doi.org/10.1103/PhysRevE.80.061908