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Science 24 July 2009:
Vol. 325. no. 5939, pp. 449 - 451
DOI: 10.1126/science.1172051
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Reports

Structural Origin of Circularly Polarized Iridescence in Jeweled Beetles

Vivek Sharma,1,2 Matija Crne,2,3 Jung Ok Park,1,2 Mohan Srinivasarao1,2,3

The iridescent metallic green beetle, Chrysina gloriosa, which selectively reflects left circularly polarized light, possesses an exoskeleton decorated by hexagonal cells (~10 µm) that coexist with pentagons and heptagons. The fraction of hexagons decreases with an increase in curvature. In bright field microscopy, each cell contains a bright yellow core, placed in a greenish cell with yellowish border, but the core disappears in dark field. With use of confocal microscopy, we observe that these cells consist of nearly concentric nested arcs that lie on the surface of a shallow cone. We infer that the patterns are structurally and optically analogous to the focal conic domains formed spontaneously on the free surface of a cholesteric liquid crystal. These textures provide the basis for the morphogenesis as well as key insights for emulating the intricate optical response of the exoskeleton of scarab beetles.

1 School of Polymer, Textile, and Fiber Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA.
2 Center for Advanced Research on Optical Microscopy (CAROM), Georgia Institute of Technology, Atlanta, GA 30332, USA.
3 School of Chemistry and Biochemisty, Georgia Institute of Technology, Atlanta, GA 30332, USA.

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THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Evolutionary Photonics with a Twist.
P. Vukusic (2009)
Science 325, 398-399
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