scholarly journals Photonic Crystal Characterization of the Cuticles of Chrysina chrysargyrea and Chrysina optima Jewel Scarab Beetles

Biomimetics ◽  
2018 ◽  
Vol 3 (4) ◽  
pp. 30 ◽  
Author(s):  
William Vargas ◽  
Esteban Avendano ◽  
Marcela Hernández-Jiménez ◽  
Daniel Azofeifa ◽  
Eduardo Libby ◽  
...  

A unified description involving structural morphology and composition, dispersion of optical constants, modeled and measured reflection spectra and photonic crystal characterization is devised. Light reflection spectra by the cuticles of scarab beetles (Chrysina chrysargyrea and Chrysina optima), measured in the wavelength range 300–1000 nm, show spectrally structured broad bands. Scanning electron microscopy analysis shows that the pitches of the twisted structures responsible for the left-handed circularly polarized reflected light change monotonically with depth through the cuticles, making it possible to obtain the explicit depth-dependence for each cuticle arrangement considered. This variation is a key aspect, and it will be introduced in the context of Berreman’s formalism, which allows us to evaluate reflection spectra whose main features coincide in those displayed in measurements. Through the dispersion relation obtained from the Helmholtz’s equation satisfied by the circular components of the propagating fields, the presence of a photonic band gap is established for each case considered. These band gaps depend on depth through the cuticle, and their spectral positions change with depth. This explains the presence of broad bands in the reflection spectra, and their spectral features correlate with details in the variation of the pitch with depth. The twisted structures consist of chitin nanofibrils whose optical anisotropy is not large enough so as to be approached from modeling the measured reflection spectra. The presence of a high birefringence substance embedded in the chitin matrix is required. In this sense, the presence of uric acid crystallites through the cuticle is strongly suggested by frustrated attenuated total reflection and Raman spectroscopy analysis. The complete optical modeling is performed incorporating the wavelength-dependent optical constants of chitin and uric acid.

1980 ◽  
Vol 34 (6) ◽  
pp. 646-651 ◽  
Author(s):  
D. G. Cameron ◽  
D. Escolar ◽  
T. G. Goplen ◽  
A. Nadeau ◽  
R. P. Young ◽  
...  

The design and construction of an infrared spectrophotometer for the quantitative measurement of attenuated total reflection spectra are described. The instrument is used to determine the optical constants of liquids as part of a study of infrared band shapes and intensities.


1968 ◽  
Vol 22 (5) ◽  
pp. 460-463
Author(s):  
Donald E. McCarthy

Reflection measurements in the infrared are useful in the determination of optical constants of materials, reststrahlen peaks, efficiency of black paints, and attenuated total reflection studies. While many papers have dealt with reflection, few have investigated the effect of the angle of incidence upon the reflection spectra. Besides angle of incidence, another important factor is the use of a collimated beam. Both of these parameters must be known and controlled for best results. Some results illustrating the effect of varying the incident angle on samples are discussed, as well as the relationship between angle of incidence and polarization.


2016 ◽  
Vol 599 ◽  
pp. 138-144 ◽  
Author(s):  
S. Jena ◽  
R.B. Tokas ◽  
P. Sarkar ◽  
J.S. Misal ◽  
S. Maidul Haque ◽  
...  

2018 ◽  
Vol 15 (148) ◽  
pp. 20180560 ◽  
Author(s):  
Giliane P. Odin ◽  
Maria E. McNamara ◽  
Hans Arwin ◽  
Kenneth Järrendahl

Scarab beetles (Coleoptera: Scarabaeidae) can exhibit striking colours produced by pigments and/or nanostructures. The latter include helicoidal (Bouligand) structures that can generate circularly polarized light. These have a cryptic evolutionary history in part because fossil examples are unknown. This suggests either a real biological signal, i.e. that Bouligand structures did not evolve until recently, or a taphonomic signal, i.e. that conditions during the fossilization process were not conducive to their preservation. We address this issue by experimentally degrading circularly polarizing cuticle of modern scarab beetles to test the relative roles of decay, maturation and taxonomy in controlling preservation. The results reveal that Bouligand structures have the potential to survive fossilization, but preservation is controlled by taxonomy and the diagenetic history of specimens. Further, cuticle of specific genus ( Chrysina ) is particularly decay-prone in alkaline conditions; this may relate to the presence of certain compounds, e.g. uric acid, in the cuticle of these taxa.


2012 ◽  
Vol 125 ◽  
pp. 219-235 ◽  
Author(s):  
Hui-Chuan Hung ◽  
Chien-Jang Wu ◽  
Tzong-Jer Yang ◽  
Shoou-Jinn Chang

2011 ◽  
Author(s):  
Xuan Guo ◽  
Lihong Han ◽  
Guifang Yuan ◽  
Zhongyuan Yu ◽  
Yumin Liu ◽  
...  

2018 ◽  
Vol 25 (5) ◽  
pp. 1433-1443
Author(s):  
C. Jansing ◽  
H. Wahab ◽  
H. Timmers ◽  
A. Gaupp ◽  
H.-C. Mertins

The complex refractive index of many materials is poorly known in the soft X-ray range across absorption edges. This is due to saturation effects that occur there in total-electron-yield and fluorescence-yield spectroscopy and that are strongest at resonance energies. Aiming to obtain reliable optical constants, a procedure that reconciles electron-yield measurements and reflection spectroscopy by correcting these saturation effects is presented. The procedure takes into account the energy- and polarization-dependence of the photon penetration depth as well as the creation efficiency for secondary electrons and their escape length. From corrected electron-yield spectra the absorption constants and the imaginary parts of the refractive index of the material are determined. The real parts of the index are subsequently obtained through a Kramers–Kronig transformation. These preliminary optical constants are refined by simulating reflection spectra and adapting them, so that measured reflection spectra are reproduced best. The efficacy of the new procedure is demonstrated for graphite. The optical constants that have been determined for linearly polarized synchrotron light incident with p- and s-geometry provide a detailed and reliable representation of the complex refractive index of the material near π- and σ-resonances. They are also suitable for allotropes of graphite such as graphene.


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