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Evolving random fractal Cantor superlattices for the infrared using a genetic algorithm.

Bossard JA, Lin L, Werner DH - J R Soc Interface (2016)

Bottom Line: Fractal geometry, often described as the geometry of Nature, can be used to mimic structures found in Nature, but deterministic fractals produce structures that are too 'perfect' to appear natural.Furthermore, we introduce fractal random Cantor bars as a candidate for generating both ordered and 'chaotic' superlattices, such as the ones found in silvery fish.We present optimized superlattices demonstrating broadband reflection as well as single and multiple pass bands in the near-infrared regime.

View Article: PubMed Central - PubMed

Affiliation: Department of Electrical Engineering, The Pennsylvania State University, 211A Electrical Engineering East, University Park, PA 16802, USA jab678@psu.edu.

No MeSH data available.


Related in: MedlinePlus

(a) Three ways found in Nature for achieving a broadband wavelength-independent reflector in a dielectric superlattice including three quarter-wave stacks, a ‘chirped’ stack and a ‘chaotic’ stack, inspired by Parker [5]. (b) Organisms with broadband optical reflectivity. (Left) Gold chrysalis of the butterfly Euploea core with ‘chirped’ superlattice [13]. (Top right) Ultraviolet photograph of a silvery fish with ‘chaotic’ superlattice [5]. (Bottom right) Gold beetle Anoplognathus parvulus with ‘chirped’ superlattice [5]. (Online version in colour.)
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RSIF20150975F1: (a) Three ways found in Nature for achieving a broadband wavelength-independent reflector in a dielectric superlattice including three quarter-wave stacks, a ‘chirped’ stack and a ‘chaotic’ stack, inspired by Parker [5]. (b) Organisms with broadband optical reflectivity. (Left) Gold chrysalis of the butterfly Euploea core with ‘chirped’ superlattice [13]. (Top right) Ultraviolet photograph of a silvery fish with ‘chaotic’ superlattice [5]. (Bottom right) Gold beetle Anoplognathus parvulus with ‘chirped’ superlattice [5]. (Online version in colour.)

Mentions: Superlattices, layers of homogeneous dielectric material that have contrasting refractive indices, have been identified in Nature in the skin of a variety of organisms that give rise to the spectral and polarized scattering of light off the organism [5–11]. Of particular interest is the variety of superlattice structures in Nature identified by Parker that give rise to broadband reflection, including tuned quarter-wave stacks, chirped and ‘chaotic’ multilayers, which are found in the herring, gold beetle shells and certain silvery fish, respectively [5]. Figure 1a illustrates these three types of superlattices found in Nature that give rise to broadband reflectivity, and photographs of several organisms with broadband reflectivity are shown in figure 1b. According to Parker, the first two superlattice types achieve broadband reflectivity by reflecting progressively smaller wavelengths at increasing depths within the superlattice. For instance, in the case of the tuned quarter wavelength stacks, each stack would be tuned to a different colour of light, and for the chirped superlattice, the decreasing layer thicknesses reflect decreasing wavelengths of light. In both cases, this leads to broadband reflectivity from the skin of the organism. In the third case, the superlattice for the silvery fish is characterized by Parker as ‘chaotic’ with no underlying order to the thicknesses of the lattice layers (i.e. they are modelled as purely random). However, such ‘chaotic’ geometries found in Nature may, in fact, arise from an underlying order that can be mimicked through variable fractal geometry.Figure 1.


Evolving random fractal Cantor superlattices for the infrared using a genetic algorithm.

Bossard JA, Lin L, Werner DH - J R Soc Interface (2016)

(a) Three ways found in Nature for achieving a broadband wavelength-independent reflector in a dielectric superlattice including three quarter-wave stacks, a ‘chirped’ stack and a ‘chaotic’ stack, inspired by Parker [5]. (b) Organisms with broadband optical reflectivity. (Left) Gold chrysalis of the butterfly Euploea core with ‘chirped’ superlattice [13]. (Top right) Ultraviolet photograph of a silvery fish with ‘chaotic’ superlattice [5]. (Bottom right) Gold beetle Anoplognathus parvulus with ‘chirped’ superlattice [5]. (Online version in colour.)
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4759801&req=5

RSIF20150975F1: (a) Three ways found in Nature for achieving a broadband wavelength-independent reflector in a dielectric superlattice including three quarter-wave stacks, a ‘chirped’ stack and a ‘chaotic’ stack, inspired by Parker [5]. (b) Organisms with broadband optical reflectivity. (Left) Gold chrysalis of the butterfly Euploea core with ‘chirped’ superlattice [13]. (Top right) Ultraviolet photograph of a silvery fish with ‘chaotic’ superlattice [5]. (Bottom right) Gold beetle Anoplognathus parvulus with ‘chirped’ superlattice [5]. (Online version in colour.)
Mentions: Superlattices, layers of homogeneous dielectric material that have contrasting refractive indices, have been identified in Nature in the skin of a variety of organisms that give rise to the spectral and polarized scattering of light off the organism [5–11]. Of particular interest is the variety of superlattice structures in Nature identified by Parker that give rise to broadband reflection, including tuned quarter-wave stacks, chirped and ‘chaotic’ multilayers, which are found in the herring, gold beetle shells and certain silvery fish, respectively [5]. Figure 1a illustrates these three types of superlattices found in Nature that give rise to broadband reflectivity, and photographs of several organisms with broadband reflectivity are shown in figure 1b. According to Parker, the first two superlattice types achieve broadband reflectivity by reflecting progressively smaller wavelengths at increasing depths within the superlattice. For instance, in the case of the tuned quarter wavelength stacks, each stack would be tuned to a different colour of light, and for the chirped superlattice, the decreasing layer thicknesses reflect decreasing wavelengths of light. In both cases, this leads to broadband reflectivity from the skin of the organism. In the third case, the superlattice for the silvery fish is characterized by Parker as ‘chaotic’ with no underlying order to the thicknesses of the lattice layers (i.e. they are modelled as purely random). However, such ‘chaotic’ geometries found in Nature may, in fact, arise from an underlying order that can be mimicked through variable fractal geometry.Figure 1.

Bottom Line: Fractal geometry, often described as the geometry of Nature, can be used to mimic structures found in Nature, but deterministic fractals produce structures that are too 'perfect' to appear natural.Furthermore, we introduce fractal random Cantor bars as a candidate for generating both ordered and 'chaotic' superlattices, such as the ones found in silvery fish.We present optimized superlattices demonstrating broadband reflection as well as single and multiple pass bands in the near-infrared regime.

View Article: PubMed Central - PubMed

Affiliation: Department of Electrical Engineering, The Pennsylvania State University, 211A Electrical Engineering East, University Park, PA 16802, USA jab678@psu.edu.

No MeSH data available.


Related in: MedlinePlus