Light manipulation principles in biological photonic systems

© 2013 Science Wise Publishing and DE GRUYTER.The science of light and colour manipulation continues to generate interest across a range of disciplines, from mainstream biology, across multiple physicsbased fields, to optical engineering. Furthermore, the study of light production and manipulation is of significant value to a variety of industrial processes and commercial products. Among the several key methods by which colour is produced in the biological world, this review sets out to describe, in some detail, the specifics of the method involving photonics in animal and plant systems; namely, the mechanism commonly referred to as structural colour generation. Not only has this theme been a very rapidly growing area of physics-based interest, but also it is increasingly clear that the biological world is filled with highly evolved structural designs by which light and colour strongly influence behaviours and ecological functions.We acknowledge the financial support of DARPA contract W911NF-10-C-0069 and of AFOSR grant FA9550-10-1-0020. We also wish to thank Caroline Pouya, Helen Ghiradella, Radislav Potyrailo, Roy Sambles, Shuichi Kinoshita and Doekele Stavenga for helpful discussions

Subtle design changes control the difference in colour reflection from the dorsal and ventral wing-membrane surfaces of the damselfly Matronoides cyaneipennis.

The hind wings of males of the damselfly Matronoides cyaneipennis exhibit iridescence that is blue dorsally and green ventrally. These structures are used semiotically in agonistic and courtship display. Transmission electron microscopy reveals these colours are due to two near-identical 5-layer distributed Bragg reflectors, one placed either side of the wing membrane. Interestingly the thicknesses of corresponding layers in each distributed Bragg reflector are very similar for all but the second layer from each outer surface. This one key difference creates the significant disparity between the reflected spectra from the distributed Bragg reflectors and the observed colours of either side of the wing. Modelling indicates that modifications to the thickness of this layer alone create a greater change in the peak reflected wavelength than is observed for similar modifications to the thickness of any other layer. This results in an optimised and highly effective pair of semiotic reflector systems, based on extremely comparable design parameters, with relatively low material and biomechanical costs.Pete Vukusic acknowledges the financial support of AFOSR grant FA9550-10-1-0020. We thank D.G. Stavenga for critical reading of the manuscript

Classification of peacock feather reflectance using principal component analysis similarity factors from multispectral imaging data

This is the author accepted manuscript. The final version is available from the publisher via the DOI in this record.Iridescent structural colors in biology exhibit sophisticated spatially-varying reflectance properties that depend on both the illumination and viewing angles. The classification of such spectral and spatial information in iridescent structurally colored surfaces is important to elucidate the functional role of irregularity and to improve understanding of color pattern formation at different length scales. In this study, we propose a non-invasive method for the spectral classification of spatial reflectance patterns at the micron scale based on the multispectral imaging technique and the principal component analysis similarity factor (PCASF). We demonstrate the effectiveness of this approach and its component methods by detailing its use in the study of the angle-dependent reflectance properties of Pavo cristatus (the common peacock) feathers, a species of peafowl very well known to exhibit bright and saturated iridescent colors. We show that multispectral reflectance imaging and PCASF approaches can be used as effective tools for spectral recognition of iridescent patterns in the visible spectrum and provide meaningful information for spectral classification of the irregularity of the microstructure in iridescent plumage.This research was developed during a visiting research stay of Dr. José M. Medina in the Departamento de Óptica, Universidad de Granada, Spain. We thank to José Medina and Rosalía Ruiz who provided the peacock samples, to David Porcel and Juan de Dios Bueno from the Servicio de Microscopía, (Centro de Instrumentación Científica, Universidad de Granada) for technical assessment, and to the Color Imaging Group (Universidad de Granada) for their hardware partial support. JMM and JAD acknowledge the Departmento de Óptica, Universidad de Granada, Spain. PV acknowledges USAF funding (FA9550-10-1-0020)

Photonic architectures in beetles: twists and iridescence

This is the final version of the article. Available from the publisher via the DOI in this record.Made available with permission of the PublisherThe order Coleoptera is, by any standard, a prodigious showcase for the extraordi nary creativity and flexibility of the evolutionary process. Concurrent with a desire to overcome the present limitations of optical coating technologies, a number of novel and elegant reflectance mechanisms have been discovered in the realms of biological systems including 3D photonic crystals and quasi-ordered coherent scattering arrays. Beetles, in particular, possess many desirable and, crucially, tunable properties from a biomimetic perspective. Here, we provide a detailed discussion of two coleopteran structures, namely 1D multilayers and helically arranged 'Bouligand' structures, and consider their putative entomological functions and potential applications in bioinspired technologies

A highly attenuating and frequency tailorable annular hole phononic crystal for surface acoustic waves

This is the final version of the article. Available from Springer Nature via the DOI in this record.Surface acoustic wave (SAW) devices are widely used for signal processing, sensing and increasingly for lab-on-a-chip applications. Phononic crystals can control the propagation of SAW, analogous to photonic crystals, enabling components such as waveguides and cavities. Here we present an approach for the realisation of robust, tailorable SAW phononic crystals, based on annular holes patterned in a SAW substrate. Using simulations and experiments, we show that this geometry supports local resonances which create highly attenuating phononic bandgaps at frequencies with negligible coupling of SAWs into other modes, even for relatively shallow features. The enormous bandgap attenuation is up to an order-of-magnitude larger than that achieved with a pillar phononic crystal of the same size, enabling effective phononic crystals to be made up of smaller numbers of elements. This work transforms the ability to exploit phononic crystals for developing novel SAW device concepts, mirroring contemporary progress in photonic crystals.The control and manipulation of propagating sound waves on a surface has applications in on-chip signal processing and sensing. Here, Ash et al. deviate from standard designs and fabricate frequency tailorable phononic crystals with an order-of-magnitude increase in attenuation.B.J.A. acknowledges funding from the EPSRC Centre for Doctoral Training in Metamaterials, grant number EP/L015331/1

Far field scattering pattern of differently structured butterfly scales

The angular and spectral reflectance of single scales of five different butterfly species was measured and related to the scale anatomy. The scales of the pierids Pieris rapae and Delias nigrina scatter white light randomly, in close agreement with Lambert’s cosine law, which can be well understood from the randomly organized beads on the scale crossribs. The reflectance of the iridescent blue scales of Morpho aega is determined by multilayer structures in the scale ridges, causing diffraction in approximately a plane. The purple scales in the dorsal wing tips of the male Colotis regina act similarly as the Morpho scale in the blue, due to multilayers in the ridges, but the scattering in the red occurs as in the Pieris scale, because the scales contain beads with pigment that does not absorb in the red wavelength range. The green–yellow scales of Urania fulgens backscatter light in a narrow spatial angle, because of a multilayer structure in the scale body

Surface plasmons at the Brillouin zone boundary of an oblique lattice

Copyright © 2015 AIP PublishingIn periodic systems of low-symmetry, the Bragg condition for the complete interference of waves along the contour of the Brillouin zone (BZ) boundary is not generally satisfied. As a result, band-gaps do not necessarily occur at this boundary. This letter demonstrates this experimentally by recording the iso-frequency contours for surface plasmon polaritons (SPPs) supported on a diffraction grating with an underlying 2D oblique Bravias lattice. It is shown that these contours do not intersect the BZ boundary perpendicularly, as the symmetry operations of the lattice place no conditions on the surface wave interference at this boundary.Engineering and Physical Sciences Research Council (EPSRC)HP Labs BristolUSA

A dual weighted residual method applied to complex periodic gratings

An extension of the dual weighted residual (DWR) method to the analysis of electromagnetic waves in a periodic diffraction grating is presented. Using the α,0-quasi-periodic transformation, an upper bound for the a posteriori error estimate is derived. This is then used to solve adaptively the associated Helmholtz problem. The goal is to achieve an acceptable accuracy in the computed diffraction efficiency while keeping the computational mesh relatively coarse. Numerical results are presented to illustrate the advantage of using DWR over the global a posteriori error estimate approach. The application of the method in biomimetic, to address the complex diffraction geometry of the Morpho butterfly wing is also discussed

Bio-inspired band-gap tunable elastic optical multilayer fibers.

The concentrically-layered photonic structure found in the tropical fruit Margaritaria nobilis serves as inspiration for photonic fibers with mechanically tunable band-gap. The fibers show the spectral filtering capabilities of a planar Bragg stack while the microscopic curvature decreases the strong directional chromaticity associated with flat multilayers. Elongation of the elastic fibers results in a shift of the reflection of over 200 nm.Financial support from the US Air Force Offi ce of Scientifi c Research Multidisciplinary University Research Initiative under award numbers FA9550-09-1-0669-DOD35CAP, FA9550-10-1-0020 and the UK Engineering and Physical Sciences Research Council EP/G060649/1 is gratefully acknowledged. M.Ko. acknowledges the fi nancial support from the Alexander von Humboldt Foundation in form of a Feodor Lynen postdoctoral research fellowship. This work was performed in part at the Center for Nanoscale Systems (CNS), a member of the National Nanotechnology Infrastructure Network (NNIN), which is supported by the National Science Foundation under NSF award no. ECS-0335765. CNS is part of Harvard University