Circularly polarised reflection from the scarab beetle Chalcothea smaragdina: light scattering by a dual photonic structure.
Vukusic, P; Finlayson, ED; Wilts, BD; et al.Mcdonald, LT
Date: 16 June 2017
Article
Journal
Interface Focus
Publisher
Royal Society
Publisher DOI
Abstract
Helicoidal architectures comprising various polysaccharides such as chitin and cellulose have
been reported in biological systems. In some cases, these architectures exhibit stunning optical
properties analogous to ordered cholesteric liquid crystal phases. In this work, we charac-
terise the circularly polarised re
ectance and ...
Helicoidal architectures comprising various polysaccharides such as chitin and cellulose have
been reported in biological systems. In some cases, these architectures exhibit stunning optical
properties analogous to ordered cholesteric liquid crystal phases. In this work, we charac-
terise the circularly polarised re
ectance and optical scattering from the cuticle of the beetle
Chalcothea smaragdina (Coleoptera: Scarabaeidae: Cetoniinae) using optical experiments, sim-
ulations and structural analysis. The selective re
ection of left-handed circularly polarised light
is attributed to a Bouligand-type helicoidal morphology within the beetle's exocuticle. Using
electron microscopy to inform electromagnetic simulations of this anisotropic strati ed medium,
the inextricable connection between the colour appearance of C. smaragdina and the periodic-
ity of its helicoidal rotation is shown. A close agreement between the model and the measured
re
ectance spectra is obtained. In addition, the elytral surface of C. smaragdina possesses
a blazed di raction grating-like surface structure, which a ects the di use appearance of the
beetle's reected colour, and therefore potentially enhances crypsis amongst the dense foliage
of its rainforest habitat.
Physics and Astronomy
Faculty of Environment, Science and Economy
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