Directionally controlled fluorescence emission in butterflies

University of Exeter, Exeter, England, United Kingdom
Science (Impact Factor: 31.48). 12/2005; 310(5751):1151. DOI: 10.1126/science.1116612
Source: PubMed

ABSTRACT Recently developed, high-efficiency, light-emitting diodes use two-dimensional photonic crystals to enhance the extraction of otherwise internally trapped light and multilayer reflectors to control the direction of light emission. This work describes the characterization of a naturally evolved light-extraction system on the wing scales of a small group of Papilio butterflies. The efficient extraction of fluorescence from these scales is facilitated by a two-dimensional photonic crystal slab that uses a multilayer to help control emission direction. Its light-extraction function is analogous to that of the light-emitting diode.

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    ABSTRACT: Broadband light trapping effect and arrays of sub-wavelength textured structures based on the butterfly wing scales are applicable to solar cells and stealth technologies. In this paper, the fine optical structures in wing scales of butterfly Papilio peranthus, exhibiting efficient light trapping effect, were carefully examined. First, the reflectivity was measured by reflectance spectrum. Field Emission Scanning Electronic Microscope (FESEM) and Transmission Electron Microscope (TEM) were used to observe the coupling morphologies and structures of the scales. Then, the optimized 3D model of the coupling structure was created combining Scanning Electron Microscope (SEM) and TEM data. Afterwards, the mechanism of the light trapping effect of these structures was analyzed by simulation and theoretical calculations. A multilayer nano-structure of chitin and air was found. These structures are effective in increasing optical path, resulting in that most of the incident light can be trapped and adsorbed within the structure at last. Furthermore, the simulated optical results are consistent with the experimental and calculated ones. This result reliably confirms that these structures induce an efficient light trapping effect. This work can be used as a reference for in-depth study on the fabrication of highly efficient bionic optical devices, such as solar cells, photo detectors, high-contrast, antiglare, and so forth.
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    ABSTRACT: A common problem of light sources emitting from an homogeneous high-refractive index medium into air is the loss of photons by total internal reflection. Bioluminescent organisms, as well as artificial devices, have to face this problem. It is expected that life, with its mechanisms for evolution, would have selected appropriate optical structures to get around this problem, at least partially. The morphology of the lantern of a specific firefly in the genus Photuris has been examined. The optical properties of the different parts of this lantern have been modelled, in order to determine their positive or adverse effect with regard to the global light extraction. We conclude that the most efficient pieces of the lantern structure are the misfit of the external scales (which produce abrupt roughness in air) and the lowering of the refractive index at the level of the cluster of photocytes, where the bioluminescent production takes place.
    Optics Express 01/2013; 21(1):764-80. DOI:10.1364/OE.21.000764 · 3.53 Impact Factor
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    ABSTRACT: This study employed a soft lithography technique to fabricate a polydimethylsiloxane (PDMS) replica of the multi-layered scales on the upper surface of a Morpho butterfly. The bionic photonic crystal microstructure of the replicated scales was examined using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The absorptivity, reflectivity and fluorescent characteristics of the wing were measured. The results showed that the microstructural and optical characteristics of the replicated wing qualitatively agree with those of the actual wing. The contact angle for the natural wing structure and the replicated wing were about 143° and 120°, respectively. As a result, it can be inferred that the soft lithography technique employed in this study represents a viable approach for the mass production of artificial photonic crystal structures for a variety of commercial applications, including optical elements for computing and communications purposes, photonic integrated circuits, anti-counterfeiting mechanisms, and so forth.
    Current Applied Physics 03/2010; 10(2-10):625-630. DOI:10.1016/j.cap.2009.08.007 · 2.03 Impact Factor


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