Evidence for a dispersion relation of optical modes in the cuticle of the scarab beetle Cotinis mutabilis

Mendoza-Galván, A.; Muñoz-Pineda, Eloy; Järrendahl, Kenneth; Arwin, Hans

doi:10.1364/ome.4.002484

Cited by 18 publications

(28 citation statements)

References 25 publications

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“…For opaque cuticles like in C. aurata the oscillations become very weak or vanish completely. However, if sufficiently large they can be used to determine cuticle thickness and also to explore cuticle structure [21,22].…”

Section: Discussionmentioning

confidence: 99%

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Sum decomposition of Mueller-matrix images and spectra of beetle cuticles

Arwin¹,

Magnusson²,

Garcia-Caurel³

et al. 2015

Opt. Express

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Abstract:Spectral Mueller matrices measured at multiple angles of incidence as well as Mueller matrix images are recorded on the exoskeletons (cuticles) of the scarab beetles Cetonia aurata and Chrysina argenteola. Cetonia aurata is green whereas Chrysina argenteola is gold-colored. When illuminated with natural (unpolarized) light, both species reflect left-handed and near-circularly polarized light originating from helicoidal structures in their cuticles. These structures are referred to as circular Bragg reflectors. For both species the Mueller matrices are found to be nondiagonal depolarizers. The matrices are Cloude decomposed to a sum of non-depolarizing matrices and it is found that the cuticle optical response, in a first approximation can be described as a sum of Mueller matrices from an ideal mirror and an ideal circular polarizer with relative weights determined by the eigenvalues of the covariance matrices of the measured Mueller matrices. The spectral and image decompositions are consistent with each other. A regression-based decomposition of the spectral and image Mueller matrices is also presented whereby the basic optical components are assumed to be a mirror and a circular polarizer as suggested by the Cloude decomposition. The advantage with a regression decomposition compared to a Cloude decomposition is its better stability as the matrices in the decomposition are determined a priori. The origin of the depolarizing features are discussed but from present data it is not possible to conclude whether the two major components, the mirror and the circular polarizer are laterally separated in domains in the cuticle or if the depolarization originates from the intrinsic properties of the helicoidal structure.

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Section: Discussionmentioning

confidence: 99%

“…At both wavelengths, large negative values on m 41 and m 14 elements are observed. The remaining off-diagonal elements are small as well as elements m 22 and m 33 whereas m 44 is large and positive. The Mueller matrices thus exhibit properties of a circular polarizer.…”

Section: Primary Data -Examplesmentioning

confidence: 99%

Sum decomposition of Mueller-matrix images and spectra of beetle cuticles

Arwin¹,

Magnusson²,

Garcia-Caurel³

et al. 2015

Opt. Express

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“…The Chrysina genus is of particular interest since circular polarization effects have been observed in several of its many species and it was in this genus these effects were first observed. However, it should be pointed out that circular polarization effects have been observed in beetles in other subfamilies like the Cetoniinae [16,21,26]. Using Mueller-matrix spectroscopic ellipsometry (MMSE) [27] in combination with structural characterization by optical microscopy and cross-sectional scanning electron microscopy (SEM) we find that, even if there is a variation in the visual coloration and patterning of the beetles, it is possible to classify the Chrysina beetles according to two major types of polarization responses connected to two different exocuticle structures.…”

Section: Introductionmentioning

confidence: 99%

Polarizing properties and structure of the cuticle of scarab beetles from theChrysinagenus

2016

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The optical properties of several scarab beetles have been previously studied but few attempts have been made to compare beetles in the same genus. To determine whether there is any relation between specimens of the same genus, we have studied and classified seven species from the Chrysina genus. The polarization properties were analyzed with Mueller-matrix spectroscopic ellipsometry and the structural characteristics with optical microscopy and scanning electron microscopy. Most of the Chrysina beetles are green colored or have a metallic look (gold or silver). The results show that the green-colored beetles polarize reflected light mainly at off-specular angles. The gold-colored beetles polarize light left-handed near circular at specular reflection. The structure of the exoskeleton is a stack of layers that form a cusplike structure in the green beetles whereas the layers are parallel to the surface in the case of the gold-colored beetles. The beetle C. gloriosa is green with gold-colored stripes along the elytras and exhibits both types of effects. The results indicate that Chrysina beetles can be classified according to these two major polarization properties.

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“…The high reflectance observed in some beetles is due to both a large number of layers in their exoskeleton and a relative high birefringence. The latter property has a strong influence on the penetration depth of the selectively reflected mode [24].…”

Section: Anisotropic Multilayer Structuresmentioning

confidence: 99%

“…Different pitch profiles have been observed in the cuticle of beetles [24,83]. The graded pitch profile plays an important role in the polarization properties of the reflected light.…”

Section: Cuticlementioning

confidence: 99%

Optical and Structural Characterization of Natural Nanostructures

Rio¹,

Fernández²

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The spectacular biodiversity of our planet is the result of millions of years of evolution. Over this time animals and plants have evolved and adapted to different environments, developing specific behavioral and physical adaptations to increase their chances of survival. During the last centuries human's curiosity has pushed us to study and understand the phenomena and mechanisms of the nature that surrounds us. This understanding has even led to the fields of biomimetics where we seek solutions to human challenges by emulating nature. Scarab beetles (from the insect family Scarabaeidae) have fascinated humans for centuries due to the brilliant metallic shine of their chitin-rich exoskeletons and more recently for their ability to polarize reflected light. This doctoral thesis focuses on the optical characterization of the polarized reflected light from beetles in the Chrysina genus, although beetles from other genera also have been investigated. All the Chrysina beetles studied here share one characteristic, they all reflect left-handed near-circular polarized light. In some cases we also detect right-handed polarized light. We have observed two different main behaviors among the studied Chrysina beetles. Those which are green-colored scatter the reflected polarized light, whereas those with metallic appearance are broadband specular reflectors. We present a detailed analysis of the optical properties with Mueller-matrix spectroscopic ellipsometry combined with optical- and electron-microscopy studies of the exoskeletons. This allow us to create a model that reproduces the optical properties of these structures. The model consists of a chiral (helicoidal) multilayer structure with a gradual change of the pitch and a constant rotation of the optic axis of the layers. Beetles are not alone to have polarizing structures in nature and it is known that many birds and insects have the ability to detect linearly polarized light. This raises the question of whether the polarization properties of the beetles are the direct or indirect results of evolution or just pure coincidence. In order to get a better understanding of the possible reasons of this particular ability, we present a simulation study of different possible scenarios in nature where incoming light could be polarized or unpolarized, and where we consider detectors (eyes) sensitive to different states of polarized light. If the beetles are able to use this characteristic for camouflage, to confuse predators or for intraspecific communication is, however, still unknown and requires further investigation. My research results provide deeper understanding of the properties of light reflected on the beetle's exoskeleton and the nanostructures responsible for the polarization of the reflected light. The developed model could be used as bioinspiration for the fabrication of novel nano-optical devices. My results can also complement biological behavioral experiments aiming to understand the purposes of this specific optical characteristics in nature.

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Evidence for a dispersion relation of optical modes in the cuticle of the scarab beetle Cotinis mutabilis

Cited by 18 publications

References 25 publications

Sum decomposition of Mueller-matrix images and spectra of beetle cuticles

Sum decomposition of Mueller-matrix images and spectra of beetle cuticles

Polarizing properties and structure of the cuticle of scarab beetles from theChrysinagenus

Optical and Structural Characterization of Natural Nanostructures

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